Allan Guymon University of Iowa
Charles Hoyle University of Southern Mississippi
Masamitsu Shirai Osaka Prefecture University
Eric Nelson 3M Optical Sciences Division
Q1: Recent Advances in Photopolymerization
Tuesday AM, April 10, 2007
Room 2007 (Moscone West)
9:00 AM -
Introduction "Overview of New Advances in Photopolymerization" by Charles Hoyle
9:15 AM - **Q1.1
Photopolymerization of Conventional, Nanostructured and Ionic Liquid Monomers.
E. Sonny Jonsson 1 , Huanyu Wei 2 , Hui Zhou 2 , Tai Yeon Lee 2 , Todd Roper 2 , John Pojman 2 , Zulma Jiminez 2 , Charles Hoyle 2 Show Abstract
1 , Fusion UV Systems, Gaithersburg, Maryland, United States, 2 , University of Southern Mississippi, Hattiesburg, Mississippi, United States
9:45 AM - **Q1.2
Reduction of Polymerization Shrinkage Stess in Photo-cured Coatings using Structured Illumination
Peter Ganahl 1 , Chad Smith 1 , Chris Coretsopoulos 1 , Alec Scranton 1 Show Abstract
1 Chemical and Biochem. Eng, University of Iowa, Iowa City, Iowa, United States
Polymerization shrinkage is an important issue in many applications since it can lead to residual stresses which can deform the polymer or its substrate, and can undermine the optical and mechanical properties of a coating. The polymerization stresses developed in a given system depend upon a number of factors, including the molar volume change upon polymerization, the conversion profile, the geometry of the system, the modulus of the cured material and the modulus of the substrate or confinement. Common methods for addressing polymerization shrinkage stress include the use of inert fillers to limit the total volume of the system that undergoes polymerization, large monomers and oligomers to reduce percentage shrinkage, and specialty polymerizations which exhibit relatively low shrinkage (i.e. cationic ring opening polymerizations). In this contribution, a novel approach for reduction of polymerization shrinkage stress for coatings is presented. In contrast to methods which are based upon a change in the formulation to reduce the total amount of shrinkage, this new method is focused on reducing the stress produced by the shrinkage that will inevitably occur, and is therefore applicable to photopolymerization of any monomer. Specifically, the “structured illumination” method is based upon a two-stage illumination process in which the coating is first illuminated in a pattern of light and dark regions. During this structured illumination stage, unreacted monomer from the dark region will migrate in response to the polymerization and the resulting shrinkage thereby preventing the development of stress. At the end of the structured illumination stage, the system contains patterned regions of stress-free polymer among pools of unreacted monomer. After a specified duration of structured illumination, the second, flood cure, stage begins. Here the entire system is illuminated to achieve a consistently high conversion throughout the coating. Shrinkage stress may develop during this flood-cure step, especially in the regions that were dark during the structured illumination step. However the total stress is greatly reduced since much of the polymerization took place during the stress-free structured illumination stage. Experimental results confirm that over 90% of the polymerization shrinkage stress can be eliminated using this approach.
10:15 AM - Q1.3
UV Curing Materials with Thermally Degradable Property
Masamitsu Shirai 1 Show Abstract
1 Department of Applied Chemistry, Osaka Prefecture University, Osaka Japan
UV curing materials are widely used in various applications, e.g., coatings, printing inks, adhesives, photoresists, and solder masks. From the point of conventional use, UV curing systems are low VOC, highly productive, and energy saving. Crosslinked materials are insoluble in solvents and show excellent physical and/or thermal properties. It is difficult or impossible to thoroughly remove the crosslinked materials from the substrate without damaging underlying materials. However, in some cases, we need to remove the crosslinked materials from substrates. In this paper, we report novel UV curing materials which are thermally degradable and are removable from substrates after use. We have synthesized and characterized novel multi-functional epoxy monomers having a linkage of sulfonate ester or tertiary ester of carboxylic acids and multi-functional methacrylate monomers bearing acetal or hemiacetal ester linkages in a molecule. Sulfonate ester, tertiary ester, acetal, and hemiacetal ester units are thermally degradable. Photo- and thermal curing of those monomers and thermal degradation of the cured materials were studied. The UV curing of multi-functional epoxy monomers bearing sulfonate ester linkages was performed using conventional photoacid generators (PAG). The curing efficiency for those monomers was dependent on PAG used and monomer structures. The cured materials became soluble in aqueous alkaline solution due to thermal dissociation of sulfonate ester linkages to sulfonic acid if baked at 120-200 oC. The UV curing of multi-functional methacrylate monomers bearing acetal or hemiacetal ester linkages was carried out using conventional photoradical initiator under nitrogen. The curing efficiency was slightly dependent on monomer structure. The cured materials containing acetal linkages started to thermally decompose at 177-236 oC and the cured ones containing hemiacetal ester linkages thermally decomposed slightly lower temperatures at 156-196 oC. The monomers containing both a photoradical initiator sensitive to 365nm light and a PAG sensitive to 254nm light were cured on irradiation with 365nm light. The cured materials became soluble in solvents if irradiated at 254 nm and followed by baking at given temperatures (60-100 oC), depending on the structure of monomers and PAG used.The present UV curing materials are highly functionalized materials and also those materials are environmentally friendly materials because they can be used as re-workable materials.
10:30 AM - **Q1.4
Photoinduced Stress Relaxation in Crosslinked Polymers
Christopher Bowman 1 2 , Timothy Scott 1 , Christopher Kloxin 1 , Neil Cramer 1 Show Abstract
1 Chemical and Biological Engineering, University of Colorado, Boulder, Colorado, United States, 2 , University of Colorado Health Sciences Center, Aurora, Colorado, United States
Tuesday, April 10New Presenter - *Q1.4 @ 9:30 amPhotoinduced Stress Relaxation in Crosslinked Polymers. Neil Cramer.
11:30 AM - **Q1.5
Photopolymerization in the Presence of Inert Diluents.
Ewa Andrzejewska 1 , Monika Janaszczyk 1 , Izabela Stepniak 1 , Malgorzata Podgorska 1 , Mats Johannson 1 Show Abstract
1 Faculty of Chemical Technology , Poznan University of Technology, Poznan Poland
Tuesday, April 10New Presenter - *Q1.5 @ 10:30 amPhotopolymerization in the Presence of Inert Diluents. Mats Johannson
12:00 PM - **Q1.6
Can We Mimic the UV-curing on a Draw Tower using Kinetics?
Johan Jansen 1 , Theo Zwartkruis 1 , Keqi Gan 2 , Vladimir Ivanov 3 Show Abstract
1 PM-CT, DSM Research, Geleen Netherlands, 2 , DSM Desotech, Elgin, Illinois, United States, 3 , University of Moscow, Moscow Russian Federation
Q2: Cationic/Nanostructured Materials
Tuesday PM, April 10, 2007
Room 2007 (Moscone West)
2:30 PM - **Q2.1
Design of Laser Ablatable Photopolymerizable Polymer Films.
Dean Webster 1 2 , Zhigang Chen 2 Show Abstract
1 Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota, United States, 2 Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, North Dakota, United States
3:00 PM - Q2.2
Structure-Property Relationship in Photopolymerizable Polymer Networks Demonstrating Shape Memory Behavior.
Alicia Ortega 1 , Scott Kasprzak 2 , Christopher Yakacki 1 , Alan Greenberg 1 , Ken Gall 3 2 Show Abstract
1 Mechanical Engineering, University of Colorado, Boulder, Colorado, United States, 2 Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 School of Materials Science and Engineering , Georgia Institute of Technology, Atlanta, Georgia, United States
The goal of this study is to investigate the fundamental relationship between structure and thermomechanical properties of photopolymerizable network polymers demonstrating shape memory behavior. Model system networks were formed by copolymerization of tert-butyl acrylate (tBA) with di(ethylene glycol) dimethacrylate (DEGDMA) or poly(ethylene glycol dimethacrylate) (PEGDMA). The degree of crosslinking was systematically varied by modifying the weight percent (wt%) of the crosslinking agent added to the tBA prior to polymerization. Compositions evaluated contained 0, 2, 4, 10, 20, 40, and 100 wt% of the crosslinking agent, respectively. Polymerization was carried out at room temperature using 2,2-Dimethoxy-2-phenylacetophenone as the initiator. The structure of the resulting material was examined via multiple physical and mechanical characterization techniques and is discussed in the context of the resulting thermomechanical properties. The equilibrium swelling decreased as the weight percent crosslinking agent increased, confirming that an increase in the crosslink density of the system was achieved. Dynamic mechanical analysis of the polymer system showed that the glass transition temperature varied with composition. The glass transition temperature (Tg) increased with increasing DEGDMA content demonstrating that the crosslinking effect was dominate in this network system; however, the Tg decreased with increasing PEGDMA content indicating that a copolymer effect dominates with longer crosslinks. As expected, the rubbery modulus of the networks increased with an increase in crosslink density. The complex nature of crosslinking on the shape memory behavior of this novel network polymer system will be described. Improved understanding of this relationship is critical for optimizing system response for a range of engineering applications including those focused on implantable biomaterials.
3:15 PM - Q2.3
Cationic Photopolymerizations: Long-Lived Cationic Active Centers
Beth Ficek 1 , Alec Scranton 1 Show Abstract
1 Chemical and Biochem. Eng, University of Iowa, Iowa City, Iowa, United States
Photopolymerizations offer many advantages over traditional thermopolymerization, (such as temporal and spatial control of initiation, cost efficiency, and solvent-free systems) and are well-established as the preferred option for a variety of films and coating applications. While the vast majority of commercial photopolymerizations involve free radical active centers, cationic photopolymerizations (in which the propagating active center is positively charged) offer a unique set of attributes. For example, since the cationic active centers do not possess an unpaired electron, they do not react with molecular oxygen, and do not consume one another in termination reactions. This non-terminating nature can lead to very long cationic active center lifetimes (hours or even days). As a consequence, cationic polymerization may proceed long after the irradiation has ceased, leading to extensive dark cure, or post-polymerization. In this contribution, post-polymerization in cationic photopolymerizations of oxiranes and oxetanes is examined and its potential for enabling new applications is discussed.
3:30 PM - **Q2.4
High Performance Photo-curable Polymers and Oligomers Based on Novel Ring-opening Reactions of Oxetanes
Tadatomi Nishikubo 1 , Hiroto Kudo 2 Show Abstract
1 Department of Material and Life Chemistry, Faculty of Engineering, Kanagawa University, Yokohama Japan, 2 Department of Material and Life Chemistry, Faculty of Engineering, Kanagawa University, Yokohama Japan
About 15 years ago, we have interested in developing new reactions of oxetanes, and successfully found certain new ring-opening addition reactions of oxetanes.In this paper, we report synthesis of oxetane monomers, synthesis and photochemical reaction of high performance oligomers and polymers with pendant oxetanyl groups, development of new reactions of oxetanes, and synthesis and photochemical reaction of methacrylate oligomers and polymers based on the reactions of oxetanes, as follows (1 - 4):1. We examined the synthesis and photochemical reaction of poly(ester)s, calixarene derivatives and polyimides with pendant oxetanyl groups, and it was found that the corresponding cured materials were obtained after photo-irradiation in the film state.2. The polyaddition of bis(oxetane)s with dicarboxylic acids and methacrylic acids proceeded under appropriate conditions to produce linear poly(ester)s (oxetane-acrylate) with primary pendant hydroxyl groups in the side chain and terminal (meth)acryloyl groups at the end of the polymer chain. This reaction system can be applied to the synthesis of photo-curable hyperbranched polyesters containing many terminal (meth)acryloyl groups. 3. Hyperbranched poly(ether)s with an oxetanyl group and many terminal hydroxyl groups [poly(EHO) and poly(BHO)] were also synthesized by the anionic ring-opening polymerization of 3-alkyl-3-hydroxymethyloxetane (EHO) or 3,3-bis(hydroxymethyl)oxetane (BHO) using potassium tert-butoxide and 18-crown-6-ether at 120-180 degrees. Poly(EHO) was reacted with (meth)acryloyl chloride to produce new photo-curable hyperbranched poly(ether)s [poly(EHO-MA)]. However, degrees of branching of poly(EHO) were not high enough (0.18-0.30). Therefore, we examined further chemical modification of poly(EHO), and successfully synthesized certain photo-curable pseudo-dendrimers and pseudo-poly(dendron)s. Poly(EHO-Ac) containing one oxetanyl group and many terminal acetoxy groups was synthesized by the reaction of poly(EHO) with acetic anhydride, and then the cationic polymerization of poly(EHO-Ac) and copolymerization with (3-ethyl-3-phenoyethyl)oxetane (EPO) were performed. 4. Pseudo-dendrimers containing many terminal hydroxyl groups were prepared in good yields by the addition reaction of polyfunctional carboxylic acid such as TMA with poly(EHO). Then, photo-curable pseudo-dendrimers containing many terminal (meth)acryloyl groups were synthesized by the reaction of the resulting pseudo-dendrimers with methacrylic anhydride and cyclic carboxylic anhydride. The synthesis of other type of pseudo-dendrimer and photo-curable pseudo-dendrimer were prepared by the cationic copolymerization of poly(EHO-Ac) with small amounts of bis(oxetane), followed by the hydrolysis and the reaction with methacrylic anhydride. The photochemical reaction of the resulting pseudo-poly(dendron)s and pseudo-dendrimers with many terminal (meth)acryloyl groups were examined.
4:15 PM - **Q2.5
Nanostructured Coatings Obtained Via Cationic UV-Curing.
Marco Sangermano 1 , Roberta Bongiovanni 1 , Giulio Malucelli 1 , Aldo Priola 1 , Ezio Amerio 1 , Anna Di Gianni 1 , Doris Pospiech 2 , Brigitte Voit 2 Show Abstract
1 Scienza dei Materiali e Ingegneria Chimica, Politecnico di Torino, Torino Italy, 2 , 2Leibniz Institute of Polymer Research Dresden, Dresden Germany
Nanostructured coatings were prepared by UV-initiated cationic polymerization of epoxy resins. To achieve this goal different methods were followed and here are reported.Silica or titania nanoparticles were directly dispersed in the epoxy resin, followed by photocuring of the mixtures. A homogeneous distribution of the inorganic particles within the polymer matrix and a good interfacial adhesion between the two phases was achieved and attributed to a chain transfer mechanism involving hydroxyl groups present on the surface of the fillers.In parallel, a dual-curing process, which involved photopolymerization and subsequent hydrolysis and condensation reactions of alkoxysilane or alkoxytitanate groups, was used in order to prepare organic-inorganic nano-hybrid networks. TEM analysis indicated the formation of the inorganic phases at nanometric level, which induced an important improvement of the mechanical properties and thermal stability of cured networks. Nanostructured thermoset polymeric coatings were also obtained from nanophased-separated block copolymer/epoxy resin mixtures. The UV-induced curing hindered the mobility of the block-copolymers in the matrix, thus maintaining the nanophase-separated structure in the obtained networks. This latest approach will yield optically transparent homogeneous materials with improved mechanical properties and also strong candidates as template for the production of nanocomposite coatings.
4:45 PM - **Q2.6
Preparation of Polysilane-Inorganic Nano-Hybrid Materials and Their Photo-induced Properties
Kimihiro Matsukawa 1 , Yukihito Matsuura 1 Show Abstract
1 Electronic Materials, Osaka Municipal Technical Research Institute, Osaka Japan
Polysilanes are well-known as photo-functional silicon based polymers, which have a high quantum efficiency of photoluminescence (PL), a high hole drift mobility, a significant photobreaching property, high refractive index, etc. These specific properties are associated with “σ-conjugation” along the Si-Si main chains. And the organic-inorganic nano-hybrids are recently noted as one of most attractive materials with improved properties compared to each single materials. Therefore, the organic-inorganic nano-hybrids, which photo-functional polysilanes as the organic component are molecularly dispersed in the inorganic matrix, are extremely interesting materials with large possibility of new functions. For the preparation of polysilane-inorganic nano-hybrids by a sol-gel method using metal alkoxides, the chemical modification of polysilane is necessary, because polysilane components should be interacted with metal hydroxides. As polysilanes are worked as macro-photoinitiators by silyl radicals generated from their photodecomposition, polysilane block-copolymers with remained half size of polysilane segments can be synthesized by a photopolymezation of acrylic monomers containing reactive groups with metal hydroxides in a sol-gel method. For example, polymethylphenylsilane (PMPS)-acryloxypropyltrialkoxysilane block copolymers were prepared by a radical polymerization with corresponding acrylates, and the PMPS-silica nano-hybrid was formed by a sol-gel method with tetraethoxysilane. The great difference in refractive index between irradiated and non-irradiated part of PMPS-silica nano-hybrid thin films was generated by UV irradiation and development, since the photodecomposed PMPS segments were quite soluble with organic solvents. And the stable refractive index pattern was fabricated from a mask-irradiated PMPS-silica nano-hybrid thin film, followed by overall UV irradiation and heat treatment. In the case of polydihexylsilane (PDHS), the conformation of Si-Si main chains was changed by the temperature, high temperature (cisoid) and low temperature (transoid), and these absorption maxima was shifted as a so-called thermochromism. The conformation of PDHS segments in PDHS-zirconia nano-hybrid thin films was fixed in cisoid structure even at low temperature. It was found that PDHS segment were encapsulated strongly in the rigid zirconia matrix. The refractive index of PDHS-zirconia nano-hybrid was changed linearly compared with a mere PDHS thin film, and the thermo-optics coefficient, the refractive index change depend on temperature, was rather higher than glass and PMMA. On the other, as polysilane has an effective photo-reducing ability of noble metal ions, gold and palladium nanoparticles were prepared by using polysilane block-copolymers with a protective action. The thin films containing palladium nanoparticles formed by UV irradiation and heat treatment could be used for the catalytic layer of the copper electroless plating.
5:15 PM - Q2.7
Effects of Polymerizable Dispersants on Photopolymerized Clay-Polymer Nanocomposite Properties.
Kwame Owusu-Adom 1 , Allan Guymon 1 Show Abstract
1 Department of Chemical & Biochemical Engineering, University of Iowa, Iowa City, Iowa, United States
Clay-polymer nanocomposites are a new class of materials that has higher mechanical and thermal properties than pristine polymers. Recent interest in these nanocomposite materials arise from the fact that significant improvement in thermal and mechananical properties occur when small concentrations of clay are added. In this study, nanocomposite materials were modified with polymerizable surfactants that copolymerize into the nanocomposite network. Effects of the immobilized polymerizable dispersants and nanoclay morphology on thermo-mechanical and photopolymerization kinetics of polyacrylate-clay nanocomposites were studied. Results show that exfoliation behavior of the clay nanoparticles depended on the surfactant chemistry. Higher storage modulus materials were obtained for highly exfoliated systems. The extent of exfoliation/inetercalation affected the photopolymerization kinetic behavior. Organoclays that retained their ordered morphology during photopolymerization showed increased polymerization rates in a series of reactive quaternary ammonium surfactants. The proximity of the reactive group on the surfactant also influenced the polymerization behavior. Even with disordered clay morphology, surfactants bearing the polymerizable dispersants at the end of their aliphatic chain showed increased polymerization rates. These polymerizable surfactants open new avenues for enhancing thermo-mechanical properties of nanocomposites while controlling the photopolymerization behavior of the nanocomposite materials.
5:30 PM - Q2.8
The Study of an Oxetane Toughened Cationic UV Curable Coating Material for Anti-fouling and Fouling Release Applications
Zhigang Chen 1 , Bret Chisholm 1 Show Abstract
1 Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, North Dakota, United States
A difunctional oxetane monomer was used to copolymerize with an epoxy siloxane oligomer during cationic photopolymerization, the resulting material shows enhanced coating properties and promising anti-fouling/fouling release performance. UV curable materials are promising candidates for future non-leaching, environmental friendly, anti-fouling/fouling release coatings for marine vehicles, which is due to their higher productivity, versatile material properties and inherent low VOC levels. Cationic UV curable materials excel free radical UV curable ones due to their better adhesion, no oxygen inhibition and low monomer/oligomer sensitization. Commercially available cationic UV curable release coatings based on epoxy-siloxane chemistry show good release performance but suffer from poor coating mechanical properties. A difunctional oxetane monomer was used to copolymerize with the epoxy-siloxane oligomer at loading levels varying from 10% to 40% weight. The resulting coating material remained hydrophobic before and after water immersion, with enhanced solvent resistance, impact resistance, hardness and modulus. These oxetane toughened coatings have macroscopic smoothness but surface micro-domains were found on the coatings containing 10% and 20% oxetane by Atomic Force Microscopy (AFM). The pseudo-barnacle shear release force for the coating containing 10% oxetane is similar to the original epoxy-siloxane release coating. The release force increases with increasing oxetane level in the coating. No leachate toxicity was found for these coatings in C. lytica and Navicula bioassay, while reduced Navicula biofilm growth was observed on oxetane containing coating surface.
Q3: Poster Session: Advances in Photo Initiated Polymer Processes and Materials
Tuesday PM, April 10, 2007
Salon Level (Marriott)
9:00 PM - Q3.1
UV-curable Organic-Inorganic Hybrid Materials by Ene-Thiol Reaction
Kimihiro Matsukawa 1 , Takeshi Fukuda 2 , Hideki Goda 2 Show Abstract
1 Electronic Materials, Osaka Municipal Technical Research Institute, Osaka Japan, 2 , Arakawa Chemical Industries Ltd., Osaka Japan
Organic-inorganic hybrids are molecularly dispersed nano-composites of organic and inorganic components, which are recently noted as most attractive materials with improved properties compared to each single materials. They are expected to become new functional materials for versatile advanced applications in the electronic and optical fields. The organic polymer-silica hybrids are generally prepared from dispersing polymers or progressing polymerization in a sol-gel reaction. However, as alcohol and water are generated by the hydrolysis and condensation of metal alkoxides in a sol-gel reaction for the formation of inorganic components, it is difficult to produce a thicker film of organic-inorganic hybrids because of a occurrence of crack by shrinking the hybrid materials. Furthermore, disadvantages of the sol-gel reaction are the need of longer time and heat treatment. For resolving these defects, we have studied the preparation of organic-silica hybrids using photocurable silsesquioxanes that are pre-condensed from trialkoxysilanes. In order to prepare the less shrinking hybrids from the crosslinking reaction of silsesquioxanes with organic components, the photo-initiated addition reaction is preferable to the photo-radical polymerization. In this work, Ene-Thiol reaction with thiol-containing silsesquioxanes and multifunctional allyl compounds was carried out without any photoinitiators. The thiol-containing silsesquioxanes could be prepared from the condensation of mercaptopropyltrimethoxysilane by several reaction conditions. When triallyl isocyanurate as multifunctional allyl compounds was reacted with the thiol-containing silsesquioxanes under UV irradiation, the photo-cured hybrid materials showed some specific properties in addition to low shrinkage, such as high transparency, high refractive index, good adhesion toward glass, and thick film formation. Furthermore, the light resistance of these photo-curable hybrids was superior to the case of photocured acrylate because these hybrids have no coloration due to the decomposition of photoinitiators. And also, these hybrid materials had the high heat resistance compared to the usual Ene-Thiol cured materials. Therefore, these photo-curable hybrids are expected to be one of new candidates for the optical materials.
9:00 PM - Q3.10
Demonstration of Polymerization for Signal Amplification in a Diagnostic Test for Influenza.
Hadley Sikes 1 , Ryan Hansen 1 , Leah Johnson 1 , Robert Jenison 2 , John Birks 3 , Kathy Rowlen 4 5 , Christopher Bowman 1 6 Show Abstract
1 Chemical and Biological Engineering, University of Colorado, Boulder, Colorado, United States, 2 , Inverness Medical-Biostar, Louisville, Colorado, United States, 3 , 2B Technologies, Boulder, Colorado, United States, 4 Chemistry and Biochemistry, University of Colorado, Boulder, Colorado, United States, 5 , InDevR, LLC, Boulder, Colorado, United States, 6 Restorative Dentistry, University of Colorado Health Sciences Center, Aurora, Colorado, United States
9:00 PM - Q3.11
Controlled Photolytic Degradation of PEG-based Hydrogels.
April Kloxin 1 , Andrea Kasko 3 , Kristi Anseth 1 2 Show Abstract
1 Dept of Chemical and Biological Engineering, University of Colorado at Boulder, Boulder, Colorado, United States, 3 Department of Bioengineering, University of California at Los Angeles, Los Angeles, California, United States, 2 The Howard Hughes Medical Institute, University of Colorado at Boulder, Boulder, Colorado, United States
9:00 PM - Q3.12
Bicolor(Red-Yellow) Fluorescence Patterning in Polymer Film Based on Phthalimido Carbamate as a New Group of Photobase Generator.
Kyu Ho Chae 1 , Yoo Ho Kim 1 Show Abstract
1 Applied Chemistry, Chonnam National University, Kwangju, Chonnam, Korea (the Republic of)
In recent years, the formation of fluorescent micropatterns in thin polymer film has attracted considerable interest due to their possible application in the areas of photonic/electronic devices, biosensor chips, and optical data storage. A number of methods for the formation of fluorescent micropattern have been reported. The fluorescence patterning methods can be divided into three categories such as using acid sensitive fluorescent dyes, using functional conjugated polymers, and UV irradiation induced reactions. Similar to fluorescent micropattern formation based on photogenerated acids, fluorescent micropatterning based on photogenerated base is also possible. Previously, we reported on the fluorescence micropatterning based on a photobase generator containing oxime-urethane groups using fluorescamine, a pre-fluorescent dye for amino groups. A copolymer film containing oxime-urethane groups on a silicon wafer was covered with a photomask, and irradiated with 254 nm of UV light. A latent image was produced in the irradiated area through the formation of amino groups. Treatment of the irradiated film with fluorescamine resulted in the formation of a fluorescent micropattern.In this presentation, we report on the bi-color fluorescent micropatterning based on a new polymeric photobase generator containing phthalimido carbamate groups through the use of fluorescamine and rhodamine. The photobase generation from phthalimido carbamates was studied by examining the changes in pH, fluorescence intensity, and photo-crosslinking of poly(glycidyl methacrylate) (PGMA). The photoproducts analysis of a model compound indicates that amine was produced from the photolytic cleavage of the phthalimide carbamate group. The polymer containing the phthalimido carbamate groups was prepared by the copolymerization of methyl methacrylate and phthalimido methacryloyloxyethylcarbamate, and applied to a bi-color fluorescent patterning material. A thin copolymer film on a silicon wafer was covered with a photomask and irradiated by UV light. A latent image was formed in the irradiated area through the formation of amino groups. Treatment of this latent image with fluorescamine and rhodamine, consecutively, led to the formation of the dyed image. The dyed image was observed by a conforcal microscope. Different colored, fluorescent micro-patterns were observed by the selective excitation of the dyes. The fluorescent micropattern on a polymer film showed a different fluorescent color, such as green, red, or red-yellow, depending on the excitation wavelength. This means that fluorescent images with various colors can be stored within one kind of polymer film and selectively shown by varying the excitation wavelength. We hope that this bi-color fluorescent imaging method has potential use in the development of multiple optical data storage media or full-color displays.
9:00 PM - Q3.14
Negative Tone Photodefinable Titania/polymer Nanocomposite with Block Copolymer as Binder.
Yasuharu Murakami 1 , Jie Yin 2 Show Abstract
1 , Hitachi Chemical Co., Ltd., Hitachi Japan, 2 , Shanghai Jiao Tong University, Shanghai China
9:00 PM - Q3.15
Photo Fries Rearrangement of Aryl Esters in Functional Polynorbornene: Tuning the Optical and Surface Properties of Polymeric Thin Layers.
Thomas Griesser 1 , Thomas Hoefler 1 , Georg Jakopic 2 , Wolfgang Kern 1 , Gregor Trimmel 1 Show Abstract
1 Institute for Chemistry and Technology of Organic Materials, Graz University of Technology, Graz, Styria, Austria, 2 Institute for Nanostructured Materials and Photonics, Joanneum Research, Weiz Austria
9:00 PM - Q3.16
Photopolymerization of Silicate Particles.
Charles Hoyle 1 , Tolecia Clark 1 , Sergei Nazarenko 1 , Huanyu Wei 1 , A. Senyurt 1 Show Abstract
1 , University of Southern Missisisppi, Hattiesburg, Mississippi, United States
An analysis of the photopolymerization of caged silicates will be presented. A variety of techniques including DMA, tensile, PALS and hardness measurements will be used to define the morphology effects fo the film on physical properties.
9:00 PM - Q3.2
Behaviour of Type I- and Type II-Photoinitiators in photopolymerizable aqueous Formulations
Beate Ganster 1 , Gerald Ullrich 1 , Ullrich Salz 2 , Norbert Moszner 2 , Robert Liska 1 Show Abstract
1 Inst. of Applied Synthetic Chemistry, Vienna University of Technology, Vienna Austria, 2 , Ivoclar Vivadent AG, Schaan Liechtenstein
The photoreactivity of the widely-used camphorquinone (CQ)-amine-based Type II photoinitiator (PI) system decreases significantly when used in dental acidic aqueous primer formulations. By variation of the water content and the amount of acidic monomer it has been demonstrated that the presence of water is mainly responsible for the low reactivity of the classical PI system consisting of CQ and ethyl dimethylamino benzoate (DMAB). The low reactivity of DMAB might be explained by the solubilisation and thus separation of the radical ions and hindrance of the subsequent proton transfer. Protonation of the radical anion in aqueous formulation might also be a reason. Therefore, the commercially available type I photoinitiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BAPO) was evaluated. This photoinitiator shows excellent photoreactivity and storage stability, but poor solubility in aqueous dental compositions. To overcome this problem, new oligo(ethyleneglycol)-substituted bisacylphosphine oxides were synthesized and investigated. Beside good solubility and significantly increased reactivity in aqueous acidic formulations, sufficient storage stability for industrial application was found
9:00 PM - Q3.3
New Alkyne-based Initiators for Single- and Two-Photon-induced Photopolymerization.
Niklas Pucher 1 , Christian Heller 1 , Bernhard Seidl 1 , Robert Infuhr 1 , Ladislav Kuna 2 , Anja Haase 2 , Volker Schmidt 2 , Helga Lichtenegger 3 , Juergen Stampfl 3 , Robert Liska 1 Show Abstract
1 Inst. of Applied Synthetic Chemistry, Vienna University of Technology, Vienna Austria, 2 Institute of Nanostructured Materials and Photonics, Joanneum Research, Weiz, Austria, Weiz Austria, 3 Institute of Materials Science and Technology, Vienna University of Technology, Austria, Vienna Austria
9:00 PM - Q3.4
Type II Photoinitiators with Glycine residues.
Sigrid Jauk 1 , Robert Liska 1 Show Abstract
1 Inst. of Applied Synthetic Chemistry, Vienna University of Technology, Vienna Austria
Over the last decades radiation curing became an important technique for industrial applications like protective or decorative coatings, printing inks or modern applications like the fabrication of three dimensional models in stereo lithographic processes. A key component in the radiation curable formulation is the photoinitiator (PI), which affects curing speed and double bond conversion. Benzophenone derivatives together with tertiary amine coinitiators are cheap, widely-used Type II initiators. These PIs suffer from diffusion controlled limitation of reactivity especially in viscous formulations or at higher degrees of conversion. This difficulty can be overcome by covalently binding the tertiary amine group to benzophenone using a methylene spacer. A second limitation in the activity originates from deactivation by back electron transfer. This can be avoided by using glycine based coinitiators which react under spontaneous decarboxylation after the electron transfer step. In the present studies, several chromophores like benzophenone-, benzil-, thioxanthone- and acridone derivatives were linked to various glycine based amines. An outstanding performance (polymerization rate tripled compared to industrially applied reference initiators) was observed for benzophenone with covalently bound phenylglycine coinitiator. This can be attributed on one hand to the suppressed back electron transfer caused by the decarboxylation process and on the other hand to a β-vinylogous cleavage process. Mechanistic investigations and performance studies of the new PIs in comparison with industrially applied PIs will be presented.
9:00 PM - Q3.5
Singlet Oxygen Scavengers for Reduced Oxygen Inhibition in Radical Photopolymerization.
Michael Hoefer 1 , Robert Liska 1 Show Abstract
1 Inst. of Applied Synthetic Chemistry, Vienna University of Technology, Vienna Austria
9:00 PM - Q3.6
Development of Bone Replacement Materials using Stereolithography.
Monika Schuster 1 , Claudia Turecek 2 , Franz Varga 2 , Helga Lichtenegger 3 , Juergen Stampfl 3 , Robert Liska 1 Show Abstract
1 Inst. of Applied Synthetic Chemistry, Vienna University of Technology, Vienna Austria, 2 Ludwig Boltzmann Institute of Osteology, Hanusch-Krankenhaus, Vienna Austria, 3 Institute of Materials Science and Technology, Vienna University of Technology, Vienna Austria
9:00 PM - Q3.7
Morphology of Tthiol-ene Based Reflective H-PDLCs.
Jeremy Wofford 1 2 , Lalgudi Natarajan 1 3 , Pamela Lloyd 1 4 , Vincent Tondiglia 1 3 , Richard Sutherland 1 3 , Dean Brown 1 2 , Timothy Bunning 1 , Rachel Jakubiak 1 , Richard Vaia 1 Show Abstract
1 AFRL, Materials and Manufacturing Directorate, WPAFB, Ohio, United States, 2 , SOCHE, Wright-Patterson, Ohio, United States, 3 , Science applications International corporation, Dayton, Ohio, United States, 4 , UES, Beavercreek, Ohio, United States
9:00 PM - Q3.8
Polymerizable Lyotropic Liquid Crystals for the Creation of Nanostructured Materials.
Lucas Sievens-Figueroa 1 , C. Guymon 1 Show Abstract
1 Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa, United States
Lyotropic liquid crystals (LLC) have generated significant interest for the creation of new organic nanomaterials because of the nanometer size scale structures that they form. Several applications have been explored ranging from catalysis to chemical protection suits and nanocomposite synthesis. The primary reason that these materials have not been used more often is due to entropic limitations during the polymerization process. Therefore, before materials with controlled lyotropic structure can be created in a controllable way, the polymerization process needs to be understood. Polymerizable versions of these systems could enable the creation of new nanostructured materials by fixing the original structure using covalent bonds. In this study the effect of the polymerization kinetics and crosslinking used in the photopolymerization process on the resulting polymer structure is examined. The order/stability of the polymerized system is an important factor to consider when studying structure evolution for polymerizable surfactants. The polymerization kinetics are dependent on the order of the system, being the fastest in more ordered phases. At the same time, the stability of the phase when adding a crosslinkable mesogen has an effect on the reaction kinetics. For binary systems (polymerizable surfactant and water) the structure retention is dependent on the order while for tertiary systems (polymerizable surfactant, crosslinker, and water) the structure retention is mostly dependent on the crosslinking effect. Enhancement in the physical properties was observed for the resulting polymer, some directly related to the retention of the hexagonal structure. SEM pictures show a decrease in the voids when adding the crosslinker to the system. This behavior suggests the use of these materials for tuning pore sizes in separation applications.
9:00 PM - Q3.9
Preparation and Characterization of Poly(alkyl urethane) Acrylate oligomers for UV Curable Coating Agent
Mi Na Park 1 , Hyo Sim Kang 1 , Sun Wha Oh 2 , Young Soo Kang 1 , Byung Hyun Ahn 3 , Myung Jun Moon 4 Show Abstract
1 Chemistry, Pukyong National Univ., Busan Korea (the Republic of), 2 , Basic Science Research Institute, Busan Korea (the Republic of), 3 School of Material Science and Engineering, Pukyong National Univ., Busan Korea (the Republic of), 4 Department of Industrial Chemistry, Pukyong National Univ., Busan Korea (the Republic of)
Allan Guymon University of Iowa
Charles Hoyle University of Southern Mississippi
Masamitsu Shirai Osaka Prefecture University
Eric Nelson 3M Optical Sciences Division
Q4: Liquid Crystalline Materials
Wednesday AM, April 11, 2007
Room 2007 (Moscone West)
9:00 AM - **Q4.1
Polymer/liquid Crystal Ccomposites Based on Thiol-ene Photopolymerization.
Lalgudi Natarajan 1 2 , Vincent Tondiglia 1 2 , Jeremy Wofford 1 , Richard Sutherland 1 2 , Pamela Lloyd 1 3 , Timothy White 4 , Allan Guymon 4 , Timothy Bunning 1 Show Abstract
1 Materials and Manufacturing Directorate, AFRL, Wright-Patterson AFB, Dayton, Ohio, United States, 2 , Science Applications International Corporation, Dayton, Ohio, United States, 3 , UES Inc., Dayton, Ohio, United States, 4 Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa, United States
9:30 AM - **Q4.2
Laser Light Scattering: Realtime Non-destructive Probe of Evolving Liquid Crystal and Polymer Dispersion Micro-structure.
Joe Whitehead 1 , Garfield Warren 1 , Funda Senyurt 2 Show Abstract
1 Physics & Astronomy, University of Southern Mississippi, Hattiesburg, Mississippi, United States, 2 Polymer Science, University of Southern Mississippi, Hattiesburg, Mississippi, United States
Liquid crystal and polymer dispersions (polymer dispersed liquid crystals and holographically formed polymer dispersed liquid crystals)are typically made utilizing one of three methods of phase separation. We use laser light scattering as a non-desctructive realtime method to probe evolving micro-structure of phase separating liquid crystal and monomer/polymer mixtures. The phase separation is induced with photon-initiated polymerization. We report on the evolving morphology of phase separating mixtures of the liquid crystal E7 and thiol-ene based monomer/polymer mixtures.
10:00 AM - Q4.3
The Formation and Performance of Thiol-ene Based Holographic Polymer Dispersed Liquid Crystals (HPDLCs) Containing Fast Reacting Vinyl Monomers.
Timothy White 1 , Lalgudi Natarajan 2 , Vincent Tondiglia 2 , Pamela Lloyd 3 , Timothy Bunning 4 , Allan Guymon 1 Show Abstract
1 Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa, United States, 2 , SAIC, WPAFB, Ohio, United States, 3 , UES Inc., WPAFB, Ohio, United States, 4 ML Directorate, Air Force Research Labs, WPAFB, Ohio, United States
Thiol-ene based holographic polymer dispersed liquid crystals (HPDLCs) have recently been shown to form long-lasting diffraction gratings with improved optical properties. Previous examination of the formation of thiol-ene based HPDLCs has shown that fast polymerization kinetics and moderate polymer gel point yield polymer/LC morphology that results in better optical performance in HPDLC reflection gratings. This work examines the contribution of vinyl (ene) monomer structure to the electro-optical performance of HPDLC reflection gratings. HPDLC reflection gratings based on triallyl-1,3,5-triazine-2,4,6(1H, 3H, 5H)-trione (triazine) have 90% transmission at 450 nm, a 50% increase over gratings made from pentaerythritol allyl ether (triallyl ether). However, the diffraction efficiency (DE) of HPDLCs based on triazine is low (~10%) due to poor definition of the polymer and LC lamellae in the grating morphology. Mixing triazine monomer into HPDLC formulations containing trimethylolpropane diallyl ether (diallyl ether) produces HPDLC reflection gratings with high baseline transmission (>80% transmission at 450 nm) and overall DE of greater than 70%. As determined by real-time IR spectroscopy, adding triazine to HPDLC formulations containing diallyl ether increases both the polymerization rate and the rate of liquid-liquid demixing. Ultimately, adding triazine monomer increases the extent of LC phase separation while also decreasing LC droplet size. Adding small amounts of triazine (2 wt%) to HPDLC formulations based on NOA65 is shown to increase overall DE by 7%.
10:15 AM - Q4.4
Holographic Polymer Dispersed Liquid Crystal (HPDLC) Gratings Formed by Visible Light Initiated Thiol-ene Photopolymerization.
Jeremy Wofford 1 2 , Lalgudi Natarajan 1 3 , Vincent Tondiglia 1 3 , Stephen Siwecki 1 3 , Pamela Lloyd 1 4 , Richard Sutherland 1 3 , Timothy Bunning 1 Show Abstract
1 AFRL, Materials and Manufacturing Directorate, Wright-Patterson, Ohio, United States, 2 , SOCHE, Wright-Patterson, Ohio, United States, 3 , Science Applications International Corporation, Dayton, Ohio, United States, 4 , UES, Beavercreek, Ohio, United States
10:30 AM - Q4.5
Scattering Model for a Transmission Mode Holographic Polymer Dispersed Liquid Crystal Spectrometer.
Kashma Rai 1 , Anna Fox 1 , Adam Fontecchio 1 Show Abstract
1 ECE , Drexel University, Philadelphia, Pennsylvania, United States
Switchable and stacked holographic polymer dispersed liquid crystals(HPDLCs) act as wavelength filters, and along with a detector form a practical and useful transmission mode spectrometer. Here we develop a model using the Berreman 4x4 matrix method to theoretically formulate the scattering behavior of the stacked HPDLCs and compare it to the experimentally measured behavior of the stacks. HPDLCs are volume holograms composed of alternating layers of liquid crystal droplets and polymer-rich regions. Their refractive index mismatch creates a Bragg grating. The index mismatch is erased by applying an electric field perpendicular to the grating vector and the entire incident spectrum is transmitted through. In the field-off state the transmission notch corresponding to the grating wavelength is reflected while the rest of the source wavelengths are transmitted. The prepolymer syrup of the HPDLC is a uniform blend of monomers, photosensitive dye and liquid crystals(LCs). A grating structure is formed inside a prepolymer cell by creating a standing wave interference pattern using a laser source. Photo-polymerization of the monomers in regions of constructive interference pushes the LCs to the destructive interference regions. Multiple HPDLC gratings are thus formed with their reflection peak separated by their individual full-width-half-maximum to span a given range of spectrum. They are stacked together with an index matching fluid between them and switched individually. Sequentially switching the individual HPDLCs in the stack determines the presence or absence of particular source wavelengths. This optical setup can have applications in in-situ medical spectroscopy and in remote sensing applications such as the determination of the presence of particular essential compounds based on the characteristics of the detected wavelengths.Coherent and diffused scattering of the incident light in the HPDLCs depends on multiple parameters including the density, size, shape of the LC droplet, the index mismatch between the polymer and LC regions and the orientation of the LC droplets. The electro optic property of single HPDLCs has been studied using methods including anisotropic coupled wave theory, scattering analysis including the effects of dye doped HPDLCs and scattering based on the anisotropic size and distribution of the LCs. Traditionally in the modeling methods the grating dielectric profile is assumed to be a square wave or sinusoidal in nature. One of the advantages of using the Berreman 4x4 matrix method for modeling is the flexibility of designing different grating profiles to more closely match the experimentally observed grating structures. The modeling of the stacked cells will give us a deeper understanding of the sensitivity of the transmission spectrometer application we have developed to detect the required wavelengths of light along with an examination on the losses, optical coupling and interaction behavior due to stacking.
11:15 AM - **Q4.6
Some Advances in Liquid Crystal Elastomers: From Crosslinks Affected Ordering to Carbon Nanoparticles Enabled Actuation.
Slobodan Zumer 1 2 , Martin Chambers 1 , George Cordoyiannis 4 2 , Heino Finkelmann 3 , Zdravko Kutnjak 2 , Andrija Lebar 2 3 , Maja Remskar 2 , Bostjan Zalar 2 Show Abstract
1 Physics Department, University of Ljubljana, Ljubljana Slovenia, 2 , Jozef Stefan Institute, Ljubljana Slovenia, 4 Department of Physics and Astronomy, Katholieke Universiteit Leuven, Leuven Belgium, 3 Institute for Macromolecular Chemistry, Albert-Ludwigs-Universität, Freiburg Germany
Liquid crystal elastomers are currently of great interest due to their large thermally stimulated changes in shape. There is a number of questions related to the orientational ordering and to possible actuation that need to be answered. Therefore calorimetry and deuteron-nuclear magnetic resonance were used to study isotropic-nematic phase transition of uniformly ordered liquid crystal elastomers. We demonstrate that density of both rodlike and pointlike crosslinks strongly affect the nematic-isotropic phase transition. The observed smeared criticality is a result of a dispersion of local mechanical fields that yields a weakly disordered orientational state composed of regions that exhibit temperature profiles of the nematic order parameter ranging from first order to supercritical. On increasing crosslinks density the predominantly first order thermodynamic response transforms into a predominantly supercritical one.Further we show how one can address the question of electrical actuation of liquid crystal elastomers. We demonstrate that an existing liquid crystal elastomer can be reprocessed using conducting carbon nanoparticles dispersed in a solvent with high swelling capability. A surface layer of a network that includes a high concentration of carbon nanoparticles is formed. The repossession allows the effective resistivity of a stripe made of liquid crystal elastomer to be reduced from highly insulating values to the values useable for electrical actuation. This layer in addition withstands large changes in geometrical shape both in contraction and expansion. Utilizing a resistive “Joule” heating effect, the reprocessed system exhibits an indirect electromechanical effect characterized by a 150% length change that can be cycled for more than 10000 times.
11:45 AM - **Q4.7
Photo-initiated Polymerization and Polymerization-induced Diffusion Towards Responsive Optical and Mechanical Devices.
Dirk Broer 1 2 Show Abstract
1 Biomolecular Engineering, Philips Research, Eindhoven Netherlands, 2 Polymer Technology, Eindhoven University of Technology, Eindhoven Netherlands
12:15 PM - **Q4.8
Nanoporous Catalysts and Membranes via Photo-initiated Radical Polymerization of Lyotropic Liquid Crystal Assemblies
Douglas Gin 1 2 Show Abstract
1 Chemical & Biological Engineering, University of Colorado, Boulder, Colorado, United States, 2 Chemistry & Biochemistry, University of Colorado, Boulder, Colorado, United States
Lyotropic liquid crystals (LLCs) are amphiphilic molecules that have the ability to self-assemble in the presence of water to form fluid, yet highly ordered phase-separated assemblies with predictable nanoporous geometries. By making polymerizable analogs of LLC mesogens, LLC assemblies can be stabilized by photo-initiated radical cross-linking to generate nanoporous polymer materials with unique application properties. In this talk, we present our latest results in the design and development of photo-cross-linked LLC assemblies with new functional capabilities for heterogeneous catalysis and molecular level fine separations.
12:45 PM - Q4.9
Polymer Nanostructures through Photopolymerization in Lyotropic Liquid Crystals.
Allan Guymon 1 Show Abstract
1 Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa, United States
The ability to control nanostructure in materials has recently generated significant excitement over the past few years. While development of inorganic materials with specific structures on the nanometer size scale has been repeatedly demonstrated, similar structures in organic materials have been much more elusive. Promising routes to such materials will be discussed that utilize a combination of photopolymerization and liquid crystals to allow templating for nanostructured organic and inorganic polymers. The dynamics that govern control of the polymeric structure are strongly dependent on both liquid crystalline phase and photopolymerization behaviour. This work will focus on using lyotropic liquid crystals (LLCs), or high concentration surfactant/water mixtures, and photopolymerization to template the polymer structure. The photopolymerization behavior plays a critical role in understanding and controlling the ultimate polymer morphology. Typically, the fastest polymerization rates are observed in the more ordered phases. In fact, in certain systems, polymerization rate is ten times faster in the ordered phases when compared to an isotropic polymerization. These large increases in polymerization rate are induced by segregation and increased ordering effects that limit diffusion of growing polymer chains. Additionally, the polymerization rate substantially alters the ultimate polymer structure and physical. Using photopolymerization allows formation of periodic structures on the nanometer size scale while slower polymerization techniques such as thermal polymerization induce gross phase separation with little indication that a nanostructured template was used.
Q5: Two-photon and Photopatterning
Wednesday PM, April 11, 2007
Room 2007 (Moscone West)
2:30 PM - **Q5.1
Photopolymers for UV-Imprint Lithography and Nanofabrication
Kenneth Carter 1 , Sarav Jhaveri 1 , Isaac Moran 1 Show Abstract
1 Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts, United States
UV-assisted imprint lithography has the potential to be a breakthrough new nanofabrication technology and critically relies on the nanometer scale control of polymer properties, interfacial bonding and deformation characteristics of polymeric materials at near molecular dimensions, for their successful performance. Nanoimprint lithography is intriguing from a cost perspective since imprint systems do not require the sophisticated optics of conventional photolithography systems which reduce the image on a mask by four times with either projection or reflection optics. Rather, imprint lithography uses polymers that harden while conforming to a physical template upon exposure to ultraviolet light or upon a thermal transition. We have developed a nano-contact molding (NCM) imprint lithographic technique for the replication of nanometer-scale features using functional crosslinked photopolymer materials (figure 1). The NCM process offers many advantages over other imprint lithographic processes including the ability to utilize inexpensive templates, excellent control of the chemistry of the molded polymer and the ability to perform surface transformations via the incorporation of reactive functionality into patterned crosslinked polymers. The most critical material component in the imprint lithographic process is the photopolymerized resist layer. The photopolymer must (1) be able to undergo rapid photocuring to high conversion; (2) have good adhesion to the substrate while good release from the mold; (3) mechanical properties for image fidelity; and (4) sufficient etch resistance for pattern transfer. Our group has been investigating both acrylate and methacrylate cure chemistry as well as some alternative cure chemistries. We have also investigated the incorporation of non-silicon containing organometallic etch resistant monomers such as phosphazene ring systems. We now report our latest results in the development of alternative imprint resists as well as new advances in lift-off patterning techniques in imprint lithography.
3:00 PM - **Q5.2
Fabrication of Functional Metal/polymer Composite Microstructures.
Stephen Kuebler 1 2 , Yun-Sheng Chen 2 , Amir Tal 2 Show Abstract
1 Chemistry, University of Central Florida, Orlando, Florida, United States, 2 CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, Florida, United States
3:30 PM - **Q5.3
Single- and Two-Photon Initiated Polymerization in Rapid Prototyping
Robert Liska 1 , Monika Schuster 1 , Robert Infuhr 1 3 , Claudia Turecek 2 , Nicklas Pucher 1 , Christian Heller 1 , Bernhard Seidl 1 , Christina Fritscher 3 , Ladislav Kuna 4 , Anje Haase 4 , Volker Schmidt 4 , Helga Lichtenegger 3 , Franz Varga 2 , Juergen Stampfl 3 Show Abstract
1 Inst. of Applied Synthetic Chemistry, Vienna University of Technology, Vienna Austria, 3 Institute of Materials Science and Technology, Vienna University of Technology, Vienna Austria, 2 Ludwig Boltzmann Institute of Osteology, Hanusch-Krankenhaus, Vienna Austria, 4 Institute of Nanostructured Materials and Photonics, Joanneum Research, Weiz Austria
4:30 PM - **Q5.4
The Design of Photopolymers for Imprint Lithography.
C. Willson 1 Show Abstract
1 Chemical Engineering, The University of Texas, Austin, Texas, Texas, United States
Step and Flash Imprint Lithography is an interesting low cost alternative to traditional microlithographic processes that offers the ability to efficiently produce nanostructures at unprecedented resolution. New photopolymerizable formulations are required to enable this process. This paper will describe progress in the design and development of acrylate and vinyl ether based platforms for this application together with efforts to prepare photopolymerizable, thermally stable, materials with low dielectric constants for use in an efficient new method for fabricating the interconnect structures in microprocessors.
5:00 PM - **Q5.5
Development of OMNiMIPs: One MoNomer Molecularly Imprinted Polymers
David Spivak 1 , Melissa Collins 1 , Jason LeJeune 1 Show Abstract
1 Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana, United States
There is a tremendous interest in the analytical applications of molecularly imprinted polymers (MIPs), which can serve as the molecular recognition element of sensors, immunoassays, and separation media. However, difficulties with formulation variables and the need for empirical optimization have inhibited the widespread use of MIPs by the general scientific community. While investigating new crosslinkers for molecular imprinting, we have recently discovered a much simpler approach to MIP formation which utilizes a single crosslinking monomer, NOBE, in addition to template, solvent and initiator. We have given this molecular imprinting method the acronym “OMNiMIPs” which stands for one monomer molecularly imprinted polymers. This new formulation eliminates variables such as choice of functional monomer (FM) and crosslinker (XL), the ratio of functional monomer/crosslinker (FM/XL), and the ratio of functional monomer/template which normally complicates MIP design. The results show that the amide functionality in the crosslinker NOBE interacts sufficiently with most templates to afford molecular recognition without the need of introducing any other functional monomer. Furthermore, investigation of performance variables of OMNiMIPs toward molecular recognition indicate significant differences between these new materials and traditionally formulated MIPs. These differences and the utility of OMNiMIPs will be discussed.
5:30 PM - Q5.6
Patterning of Thin Photocurable Films into Pillar Arrays Utilizing Electrohydrodynamic Instabilities.
Elizabeth Collister 1 , Michael Dickey 1 , Allen Raines 2 , C. Willson 1 Show Abstract
1 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States, 2 Mechanical Engineering, University of Texas at Austin, Austin, Texas, United States
With the acceptance that there are physical limitations to photolithography, other patterning techniques are being sought. Directed-assembly techniques are attractive alternatives since they harness a natural phenomenon to create structures. A directed-assembly technique was found which utilizes electrohydrodynamic instabilities in thin films to create arrays of polymeric pillars. This technique may be applicable to fabricating MEMS, microfluidic devices and photonic crystals.Pillar formation is a result of the destabilization of the thin film due to an external electric field. The external electric field is created by placing electrodes above and below the thin film, leaving a small gap between the film and the top electrode. The electric field applied across the thin film amplifies the inherent undulations in the film. Once the strength of the electrostatic force is sufficient to overcome the stabilizing surface tension force the undulations span the gap and pillar arrays form. The process of pillar formation is on the order of seconds once the electric field is applied.The general material requirements for the photocurable system are the ability to form a stable thin liquid film, to cure efficiently, and to form mechanically stable structures once cured. Control of the the diameter and spacing of the pillars can be accomplished through knowledge of a variety of parameters. Photocurable systems discussed include acrylate, thiol-ene, vinyl ether, and maleimide acceptor/donor systems. The design of top electrode patterns that induce long range order will be discussed.
5:45 PM - Q5.7
Photo-patternable Imaging Layers for Controlling Block Copolymer Microdomain Orientation
Padma Gopalan 1 , Paul Nealey 2 , Insik In 1 , Young-Hye Na 2 Show Abstract
1 Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States, 2 Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
Block copolymer (BCP) thin films with vertical orientation of microdomains are of considerable interest as one of the microdomains can be easily removed resulting in patterned structures such as nanopores or nanochannels. One way of controlling the orientation of microdomains in a BCP thin film is by surface modification to tune the interfacial energies. We recently demonstrated the feasibility of using a third comonomer (C) in the random copolymer brush P(A-r-B-r-C) to precisely adjust the interfacial and surface energies of a diblock copolymer P(A-b-B) thin films over the brush layer. Here, we present a substrate independent photo-crosslinking chemistry based on a side-chain type random copolymer brush. Photo-crosslinking chemistry used in conventional photolithography was exploited to formulate patterned neutral surfaces. The photo-crosslinkable imaging layer was synthesized by esterification of HEMA hydroxy groups with acryloyl groups in a P(S-r-MMA-r-HEMA) random copolymer. The composition of the copolymer was fine tuned to tailor the wetting behavior of the top symmetric P(S-b-MMA) block copolymer film and to optimize the photo-crosslinking process. The random copolymer layer was patterned by exposure to UV irradiation through a TEM grid as a photo-mask. The exposed region resulted in a hydrophobic surface with a contact angle of 76 degrees and the unexposed region showed a contact angle of 36 degrees. A thin film of symmetric P(S-r-MMA) deposited and annealed on the patterned substrate showed vertical lamella on the exposed region and parallel lamella in the unexposed region with a clear transition at the interface. The advantages of this approach are the accessibility to (a) substrate-independent neutral surfaces for BCPs containing temperature sensitive monomers, and (b) photo-patterned substrates (silicon, gold, glass, etc) with regions of different interfacial energies resulting in patterned BCP morphologies.
Allan Guymon University of Iowa
Charles Hoyle University of Southern Mississippi
Masamitsu Shirai Osaka Prefecture University
Eric Nelson 3M Optical Sciences Division
Q6: Thiolene/Biological Applications
Thursday AM, April 12, 2007
Room 2007 (Moscone West)
9:00 AM - Q6.1
Ternary Thiol-Ene-(meth)Acrylate Systems for High Tg Low Stress Applications
Neil Cramer 1 , Jacquelyn Carioscia 1 , Christopher Bowman 1 2 Show Abstract
1 Chemical and Biological Engineering, University of Colorado, Boulder, Colorado, United States, 2 , University of Colorado Health Sciences Center, Denver, Colorado, United States
The objective of this work was to investigate ternary thiol-ene-(meth)acrylate photopolymer systems as high performance polymer and composite materials. One of the applications for these types of systems is dental materials. Modern polymer composite dental materials are composed of dimethacrylate based monomer systems that are an improvement to the more invasive amalgam fillings. However, the polymer composites have several shortcomings, including that the methacrylate monomer system leads to high polymerization shrinkage and subsequently high shrinkage stress. Ternary thiol-ene-(meth)acrylate systems proceed via a mixed mode step-chain growth radical polymerization mechanism that combines the advantages of both step-growth thiol-ene and chain growth (meth)acrylate systems. They exhibit rapid polymerization kinetics, low oxygen inhibition, and high functional group conversion. One of the primary benefits of the ternary thiol-ene-(meth)acrylate systems is a significant reduction in the polymerization shrinkage and shrinkage stress while retaining or improving physical properties as compared to di(meth)acrylate-based resin systems. Recently, we synthesized several norbornene functionalized monomers, bisphenol-A ethoxylated dinorbornene (BPAEDN) and trimethylolpropane trinorbornene (TMPTN), to improve the mechanical properties of binary thiol-ene systems. These thiol-norbornene systems utilized the thiol monomer pentaerythritol tetra(3-mercaptopropionate) (PETMP) and were shown to exhibit extremely low polymerization shrinkage and shrinkage stress. The PETMP/BPAEDN and PETMP/TMPTN systems exhibited 1.6 and 3.0% volume shrinkage respectively, relative to 5.0% volume shrinkage for a 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropyl)phenyl]propane (BisGMA)/ triethylene glycol dimethacrylate (TEGDMA) system. Additionally, the PETMP/BPAEDN and PETMP/TNPTN systems exhibited 0.4 and 0.2 MPa shrinkage stress respectively, relative to 1.8 MPa shrinkage stress for the BisGMA/TEGDMA system. Ternary thiol-norbornene-mechacrylate systems comprised of 30 wt% of a stoichiometric mixture of PETMP and TMPTN or BPAEDN, and 70 wt% EBPADMA were evaluated and found to exhibit high Tg’s. The PETMP/TMPTN/EBPADMA system exhibits a final stress of 0.35±0.12 MPa, an 80% decrease in polymerization stress relative to the BisGMA/TEGDMA dimethacrylate system. The results of our work to date show that ternary thiol-ene-(meth)acrylate systems have great promise for polymer systems requiring both good mechanical properties and low shrinkage and stress.
9:15 AM - Q6.2
Thiol-Vinyl Ether Hybrid Photopolymerization
Qin Li 1 , Huanyu Wei 1 , Moriam Ojelade 2 , Samy Madbouly 1 , Joshua Otaigbe 1 , Paige Phillips 3 , Charles Hoyle 1 Show Abstract
1 School of Polymers and High Performance Materials, University of Southern Mississippi, Hattiesburg, Mississippi, United States, 2 Department of Natural Science, University of Houston-Downtown, Houston, Texas, United States, 3 Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, Mississippi, United States
The photopolymerization kinetics of mixtures containing a trithiol and a trivinyl ether (in different molar ratio) with a cationic photoinitiator were investigated by real-time infrared and real-time rheology. This represents the first example of a thiol-ene radical/ene cationic two-step hybrid photopolymerization process in which thiol copolymerizes with vinyl ether functional groups in a rapid radical step growth process followed by vinyl ether cationic homopolymerization. The combination of the thiol-vinyl ether copolymerization and the vinyl ether cationic polymerization resulting in crosslinked networks with thermal and mechanical properties combinations of each system are unique.
9:30 AM - Q6.3
Polymerization Kinetics and Network Evolution Process of Thiol-Allyl ether-Methacrylate ternary systems
Tai Yeon Lee 1 , Zachary Smith 1 , Sirish Reddy 1 , Jacquelyn Carioscia 1 , Christopher Bowman 1 2 Show Abstract
1 Chemical and Biological Engineering, University fo Colorado, Boulder, Boulder, Colorado, United States, 2 Dental School, University of Colorado Health Science Center, Aurora, Colorado, United States
The evolution of the polymerization induced shrinkage stress and mechanical properties of thiol-allyl ether-methacrylate ternary systems and their relationship to the polymerization kinetics have been investigated. The thiol-allyl ether-methacrylate ternary systems uniquely exhibits two different polymerization regimes, a methacrylate homopolymerization dominated regime coupled with chain transfer to thiol followed by a second thiol-ene polymerization dominated regime. This polymerization mechanism is primarily due to the combination of the chemical nature of the methacrylate and allyl ether double bonds. Other ternary thiol-vinyl-vinyl systems exhibit the conversion of all functional groups increases from the initial stage of polymerization. Because methacrylate homopolymerization with chain transfer reactions to thiols dominates the initial stage of polymerization (up to 60 % of the methacrylate conversion) the concentration and structure of the thiol significantly affects the polymerization processes and polymer network structure. The methacrylate chain length significantly decreases from 20 to 1.5 with increasing thiol content, and the methacrylate conversion rate during the first polymerization regime depends linearly on the [SH]o/[methacrylate]o ratio. The overall polymerization rates and glass transition temperature increase significantly with increasing thiol functionality while the methacrylate final conversion decreases more than 20 % due to the formation of the highly crosslinked network. Due to the two distinct polymerization regimes of the ternary systems, the mechanism for the evolution of polymerization induced shrinkage stress is unique as compared to other thiol-ene and methacrylate systems. During the first polymerization stage, only intermediate molecular weight methacrylate oligomers are produced, resulting in delayed gelation and near zero shrinkage stress. Immediately following the first polymerization stage, the allyl ether begins to polymerize and shrinkage stress increases in correspondence with the increased allyl ether conversion. It is observed that the shrinkage stress of the ternary systems exhibits approximately 50 % of the shrinkage stress of the current dental restoration systems. Also, due to the two polymerization regimes, the mechanical properties evolve uniquely as compared to other ternary systems. It is noted that glass transition temperatures of the ternary systems (~ 100 oC) are much higher than traditional thiol-ene polymers and comparable to the current polymeric composites for dental restorations, indicating that the thiol-allyl ether-methacrylate systems are an excellent candidate for dental restorations. Ultimately, this work shows that thiol-allyl ether-methacrylate ternary systems have significant potential for the development of high performance polymeric resins with low shrinkage stress and enhanced mechanical properties comparable to methacrylates.
9:45 AM - **Q6.4
Development of Physical and Mechanical Properties in Photocured Adhesives.
John Woods 1 Show Abstract
1 , Henkel Corporation, Rocky Hill, Connecticut, United States
10:15 AM - **Q6.5
Photopolymerization of Monomers Derived from Natural Resources.
Mats Johansson 1 , Neil Simpson 1 , Karl Hult 2 , Mohamad Takwa 2 , Mats Martinelle 2 , Eva Malmström 1 Show Abstract
1 Fibre & Polymer Technology, Royal Institute of Technology, Stockholm Sweden, 2 Biotechnology, Royal Institute of Technology, Stockholm Sweden
Increased environmental concern in society and cost for raw materials from fossil resources has increased the interest in the development of new materials either from natural resources or by the use of biochemical reactions. The use of natural monomers has a long tradition in coating science and renewed interest in this field has evolved.(1) This has interest has also been seen in photocurable coating systems where the cationic polymerization of epoxy functional fatty acid derivatives such as vernonia oil or epoxydized soy bean oil are the most explored examples.(2) Other examples are modification of epoxy or hydroxyfunctional fatty acids with acrylates to make these free radically crosslinkable.(3)This presentation describes two approaches in the development of new photocurable systems using either natural monomers or monomers made using biocatalysis.The first part describes the use of unsaturated fatty acids as enes in photopolymerizable thiol-ene systems. The reactivity of the 1,2-disubstituted alkenes in fatty acids with thiols is rather low compared to many conventional monomers. The rate determining step in the thiol-ene reaction is in this case shown to be the abstraction of the thiol hydrogen by the secondary carbon centred radical. The thiol-ene reaction is, although slow, shown to be efficient enough for thin layer surface modification of thiol functional surfaces with very thin layers of linseed oil covalently attached to the surface. The photoinduced surface attachment of layers as thin as 40 Å is shown to be easily made and exhibit very good frictional properties for certain application.The second part describes the synthesis of acrylate and thiol functional oligomers via enzyme catalyzed reactions(4) and the photopolymerization of these monomers. The effect of variation in structure of the oligomers on the curing performance and final properties will be discussed. Oligomers with dithiol-, diacrylate- or thiol/acrylate-functionalities are readily made and photopolymerized to give polymers with properties depending on the exact structure. 1.Derksen, J. T. P.; Cuperus, F. P.; Kolster, P. Renewable resources in coatings technology: A review Prog. Org. Coat. 27, 45 (1996).2. Crivello, J. V.; Narayan, R. Chem. Mater. 4, 692 (1992)3.Khot, S. N.; Lascala, J. J.; Can, E.; Morye, S. S.; Williams, G. I.; Palmese, G. R.;Kusefoglu, S. H.; Wool, R. P. J. Appl. Polym. Sci. 82, 703 (2001) 4.Takwa, M.; Simpson, N.; Malmström, E.; Hult, K., Martinelle, M. Macromol. Rapid Commun., in press 2006
10:45 AM - Q6.6
Novel Thiols and Their Copolymerization Reactions.
Charles Hoyle 1 , Hui Zhou 1 Show Abstract
1 , University of southern missisisppi, Hattiesburg, Mississippi, United States
11:00 AM - Q6.7
Photointiated Thiol-Ene Polymerization of Perfect Networks.
Charles Hoyle 1 , Huanyu Wei 1 , Hui Zhou 1 Show Abstract
1 , University of Southern Missisisppi, Hattiesburg, Mississippi, United States
The photopolymerization of mixtures of multifunctional thiols and enes proceeds rapidly in the presence of nitrogen and air. The free-radical step growth polymerization mechanism is unique and leads to materials with highly uniform crosslink density. Due to the ability of thiols to copolymerize with virtually any ene, there is significant latitude in formulating coatings and other crosslinked materials with a wide range in physical properties. Recently, we have evaluated a variety of thiol-ene combinations including new classes of reactive enes. In addition, we have functionalized silicon derivatives to enhance and control the reactivity of photoinitiated thiol-ene systems. An overview of traditional thiol-ene polymerization will be presented to establish the basis for consideration of new processes recently developed in our lab.
11:30 AM - **Q6.8
Photoinitiated Polymerizations for the Synthesis of Hydrogel Niches for Cell Encapsulation and Tissue Engineering.
Charles Nuttelman 1 , Mark Rice 1 , Darshita Shah 1 , Benjamin Fairbanks 1 , Kristi Anseth 1 2 Show Abstract
1 Chemical and Biological Engineering, University of Colorado at Boulder, Boulder, Colorado, United States, 2 Howard Hughes Medical Institute, University of Colorado, Boulder, Colorado, United States
12:00 PM - Q6.9
Structure Property Relationships of Biomaterials Photopolymerized within Nanostructured Lyotropic Liquid Crystalline Templates
Jason Clapper 1 , Allan Guymon 1 Show Abstract
1 , The University of Iowa, Iowa City, Iowa, United States
One of the more promising methods available for the synthesis of materials with sub-micron morphologies is through the use of self-assembling media such as lyotropic liquid crystalline (LLC) solutions. In this work, various nanostructured LLCs were used as photopolymerization templates, structuring the formation of polymer networks into the specific geometry of the parent LLC. Photopolymerization is critical to the LLC templating method as it allows both rapid polymerization and temperature independence, enabling kinetic trapping of the polymer network within the temperature sensitive liquid crystalline geometry. Both commercial monomers and synthesized biodegradable monomers were templated using nanostructured LLCs, and the resulting properties and behavior of these materials were studied as a function of their induced morphology.Using select LLC mesophases to structure a common poly(ethylene glycol) diacrylate (PEGDA) hydrogel system, unique and advantageous hydrogel properties were observed with the templated gels. Specifically, as the LLC parent template and hydrogel network were directed into highly-ordered hexagonal and lamellar geometries, the resulting material exhibited a three fold increase in modulus, a 100% increase in swelling, and a three fold increase in permeability when compared to isotropic PEGDA hydrogels. By substituting biodegradable block macromers in place of non-degradable PEGDA monomers in the templating scheme, highly ordered biodegradable hydrogels were fabricated, and an increase in swelling, permeability, and degradation rate were observed over isotropic networks of the same polymer. In addition, by orientating the biodegradable macromers within nanostructured LLC mesophases, the photopolymerization rate and conversion of the forming biohydrogels were significantly increased. Due to their highly organized arrangement of polar and non-polar phases on the nanometer scale, LLC templates were also explored as a compatibilization platform for immiscible monomer blends to form polymer composite materials. It was observed that the hexagonal LLC mesophase not only served to compatibilize two commercial immiscible monomers, hexanediol diacrylate (HDDA) and PEGDA, but also yielded a composite material with additive properties from each crosslinking constituent, suggesting the formation of a type of interpenetrating network. Furthermore, by compatibilizing two immiscible biodegradable monomers within the nanodomains of a LLC mesophase, a versatile biomaterial was constructed in which the water uptake, degradation time, and mechanical strength of the composite were tightly controlled. Throughout this work, the use of LLC templates and photopolymerization resulted in biomaterials that have new and exceptional properties that can be closely tailored by selecting the geometry of the parent LLC template, or through the addition of a second polymer network uniquely compatibilized through the inherent nature of the LLC.
12:15 PM - Q6.10
New Radiation-Curable Monomers Made via Enzyme-Catalyzed Reactions.
Neil Simpson 1 , Mohamad Takwa 2 , Eva Malmstrom 1 , Karl Hult 2 , Mats Martinelle 2 , Mats J. Johansson 1 Show Abstract
1 Polymer Chemistry, Royal Institute of Technology, Stockholm Sweden, 2 School of Biotechnology, AlbaNova, Stockholm Sweden
12:30 PM - Q6.11
Feasibility and Cytocompatibility of Poly(ethylene glycol) Dimethacrylate Crosslinked Networks for Orthopedic Graft Fixation and Vascular Repair
Christopher Yakacki 1 , Robin Shandas 1 2 , Michael Lyons 1 , Alicia Ortega 1 , Ken Gall 3 4 Show Abstract
1 Mechanical Engineering, University of Colorado, Boulder, Colorado, United States, 2 Division of Cardiology, The Children's Hospital Denver, Denver, Colorado, United States, 3 School of Materials Science and Engineering, The Georgia Institute of Technology, Atlanta, Georgia, United States, 4 Woodruff School of Mechanical Engineering, The Georgia Institute of Technology, Atlanta, Georgia, United States
Photoinitiated networks exhibiting shape-memory offer the ability to improve graft fixation and vascular repair clinically. This study investigates feasibility and cytocompatibility of poly(ethylene glycol) dimethacrylate (PEGDMA) crosslinked networks for the aforementioned applications. PEGDMA was copolymerized with methyl methacrylate or tert-butyl acrylate to create shape-memory networks. The networks demonstrated a high degree of thermomechanical tailor-ability; the glass transition temperature and rubbery modulus are shown to be independently variable by controlling the amount and molecular weight of the PEGDMA crosslinker. For high force applications, such as ACL graft fixation, the rate of shape recovery was highly dependent on the glass transition temperature while the crosslink density controlled the force of shape memory. For soft tissue applications, such as stenting and vascular grafts, the rate of recovery was highly dependent on both the glass transition temperature and crosslink density. Optimized networks were selected for each application and underwent various methods of sterilization including steam, ethylene oxide, low temperature plasma, gamma and e-beam irradiation, and low temperature 'Noxilizer' gas sterilizations. Samples sterilized by all the methods showed a favorable and negative cytotoxic response except for the low temperature plasma sterilization. Dynamic mechanical analysis and FTIR-ATR were run on the irradiated and plasma-sterilized samples and indicated mechanical and chemical alterations of the network during sterilization. Finally, the results and experiences of our initial implantations in animal models are discussed. Shape-memory ACL graft fixation devices were implanted in a sheep model while vascular stents were implanted in a porcine model.