Effect of Polymer Network Formation in the Two-Photon Polymerization Process on Polymer Properties and Their Applications

Two-photon polymerization (2PP) has been used extensively for a decade to print a wide range of 3D structures with nanoscale features. Less well known is the relationship between molecular networks that are formed and the properties of the resulting polymer. This is due in part to the chemistry of conventional 2PP resins that use photo-generated free radicals to initiate reactions; a process that is difficult to control and results in limited conversion and unwanted side reactions, that in turn causes brittleness and shrinkage-induced stresses and deformation. This work investigates the benefits of using a base-catalyzed polymerization process to improve the structure’s mechanical properties (strength, fracture toughness) and reduced shrinkage (for better control of dimensions). Resins with photogenerated bases encourage highly selective thiol-Michael addition between monomers resulting in uniform chemical networks that are glassy and soften at 60-70C. Examples of applications that are possible with these resins include structures with shape-memory properties that respond external stimuli and microstructured metasurfaces for dry adhesion. Merging high-resolution 3D printing with molecular engineering of shape-memory networks can expand applications for printed structures in microfluidics, photonics, and structures that require tight dimensional control and fine resolution.<br/><br/>This material is based upon work supported by the Department of Energy [National Nuclear Security Administration ] University of Rochester "National Inertial Confinement Fusion Program" under Award Number DE-NA0004144