11:15 AM - SB07.02.04
Nanophase Separation in Triblock Copolymers—A Strategy to Achieve Low Modulus, Elastic Deformation and Good Mobility in Polymer Semiconductors
Franziska Lissel1,2
Leibniz Institute of Polymer Research1,Dresden University of Technology2
Show Abstract
The elastic modulus of polymer semiconductors (PSCs) (0.1 - 1 GPa for typical PSCs) is still orders of magnitudes away from human skin (0.1 - 10 MPa). Also, PSCs are brittle and structurally fragile, prohibiting their application in mechanically strenuous environments, or leading to the break-down of electric functionality.
Different pathways were explored to lower the modulus of PSCs, e.g. non conjugated spacers [1], changing the regioregularity of the backbone [2], or modifying the sidechains [3], to name a few. Lowering the modulus is generally associated with a decrease in mobility, and balancing the requirements of high mobility and low modulus when designing a PSC is challenging.
Here, we draw on an old concept in polymer engineering to approach the problem: Covalently linking two polymer chains into a block copolymer leads to separation on the nanoscale due to the thermodynamic incompatibility of the chains. The phases retain their respective properties (Tg, etc). A similar approach was used before to realize elongability (plastic deformation) in PSCs [4].
Combining PSCs with biocompatible elastomers in block copolymers gives materials that have a low modulus, can be deformed elastically and retain good mobility [5]. We synthesized triblock co-polymers (TBCs) by covalently end-capping poly-diketopyrrolopyrrole-thienothiophene (PDPP-TT), a high-performance D-A PSC, with two elastomeric polydimethylsiloxanes (PDMS) blocks to combine favorable electrical and mechanical properties in one system. The resulting nanophase segregation of both components, preserves the features of both moieties (PDPP-TT and PDMS) in their respective domains. The TBCs are soft and durable: the TBC with the highest PDMS content has a low modulus (6 MPa) in the range of mammalian skin and shows no crack formation up to 85% strain. The TBC achieves a mobility of 0.1 cm2V-1s-1, in the range of the fully conjugated reference polymer (0.7 cm2V-1s-1). In a doped state, the block copolymer maintains electronic functionality over more than 1500 cycles at 50% strain. Also, the TBC can be shear-coated at high speeds (up to 10 s cm-1) and still reliably give smooth films [6]. While the high speeds result in increased film thickness (up to 600 nm), no degradation of the electrical performance was observed, as was frequently reported for polymer−based OFETs.
Finally, using physisorption, organic field-effect transistor (OFET)-based biosensors can be fabricated which detect both SARS-CoV-2 antigens as well as anti-SARS-CoV-2 antibodies in less than 20 minutes. The biosensor was produced by functionalizing an intrinsically stretchable and semiconducting tri-block copolymer (TBC) film either with the anti-S1 protein antibodies (S1 Abs) or receptor-binding domain (RBD) of the S1 protein, targeting CoV-2-specific RBDs and anti S1 Abs, respectively.. The device demonstrates a high sensitivity of about 19%/dec and limit of detection (LOD) 0.36 fg/mL for anti-SARS-Cov-2 antibodies, and at the same time, a sensitivity of 32%/dec and LOD of 76.61 pg/mL for the virus antigen detection [7].
References:
[1] Mun, Wang, Oh, Katsumata, Lee, Kang, Wu, Lissel, Rondeau-Gagné, Tok, Bao: Adv. Funct. Mater. 2018, 28, 1804222.
[2] Kim, Kim, Lee, Yu, Kim, Song, Shin, Oh, Jeon, Kim, Kim: Macromolecules 2015, 48, 13, 4339.
[3] Savagatrup, Makaram, Burke, Lipomi: Adv Funct Mater 2014, 24, 1169.
[4] Müller, Goffri, Breiby, Andreasen, Chanzy, Janssen, Nielsen, Radano, Sirringhaus, Smith, Stingelin-Stutzmann: Adv. Funct. Mater. 2007, 17, 2674.
[5] Ditte, Perez, Chae, Hambsch, Al-Hussein, Komber, Formanek, Mannsfeld, Fery, Kiriy, Lissel: Adv. Mat. 2021, 2005416
[6] Ditte, Perez, Hambsch, Kiriy, Mannsfeld, Voit, Krukskaya, Lissel: Polymers 2021, 13 (9), 1435
[7] Ditte, Nguyen Le, Ditzer, Sandoval Bojorquez, Chae, Bachmann, Baraban, Lissel: under review 2021