RAFT Synthesis of Photo Cross-Linkable Tyrosine-Containing Copolymers With Self-Assembling and Thermoresponsive Properties

Tyrosine is a proteinogenic amino acid with phenol functionality. Dityrosine cross-linking is a key component in the development of novel functional biomaterials with tunable assemblies and mechanical properties. Herein, we report the synthesis of two series of photo cross-linkable tyrosine-containing copolymers by reversible addition-fragmentation chain-transfer (RAFT) copolymerization of N-acryloyl-L-tyrosine (ATyrOH) with N-acryloyl-L,L-diphenylalanine (APhePheOH) acting as a self-assembling motif and N-isopropylacrylamide (NIPAM), exhibiting thermoresponsive properties. P(APhePheOH-co-ATyrOH)s with different co-monomer compositions afforded self-assembled structures (rigid and flexible fibers with different diameters and lengths). Dityrosine bond formation of P(APhePheOH-co-ATyrOH) was investigated under LED-UV irradiation (lambda = 265 nm), which was evaluated by comparison of the blue fluorescence excitation-emission at 405 nm. Owing to the presence of the carboxylic acid unit and the phenol functionality of ATyrOH, P(NIPAM-co-ATyrOH)s displayed thermo- and pH-responsive properties, depending on the composition, and blue luminescence induced by the photo cross-linking reaction.