Development of a Versatile Methodology for the Synthesis of Poly(2,5-benzophenone) Containing Coil−Rod−Coil Triblock Copolymers

A short, simple, versatile methodology was developed for the synthesis of poly(2,5-benzophenone) containing coil−rod−coil triblock copolymers. After a model study, poly(2,5-benzophenone) macroinitiators were synthesized via end-capping poly(2,5-dichlorobenzophenone) synthesized by Ni(0)-catalyzed polymerization and functionalization of the chain ends utilizing phase transfer chlorination. Varying molecular weights of polystyrene-b-poly(2,5-benzophenone)-b-polystyrene were synthesized using the macroinitiators in the atom transfer radical polymerization of styrene. The materials were characterized by gel permeation chromatography, nuclear magnetic resonance, differential scanning calorimetry, and transmission electron microscopy. Applications were explored through dynamic mechanical analysis and the construction of a distributed junction photovoltaic device

Photoresponsive Polyesters for Tailorable Shape Memory Biomaterials

The synthesis of a library of poly­(ester urethane)­s (PEUs) containing pendant photoresponsive moieties afforded through the incorporation of one of two novel bifunctional monomers resulted in degradable materials with a range of tunable thermal and mechanical properties. Utilizing light irradiation, macroscopic temporary shapes were fixed by increasing the cross-link density of a thermoset network via photoinduced reversible [2 + 2] cycloaddition of cinnamamide or cinnamate pendant groups under UV light (λ = 302 nm). Further irradiation with UV light (λ = 254 nm) led to the cleaving of the temporary cross-links and recovery of the original shape. Examination of these materials under physiological conditions displayed tunable degradation with rates faster than PCL-based materials, and initial biocompatibility studies exhibited negligible cytotoxicity for HeLa cells based on results of ATP assay. The ability to tune thermal properties also allowed specific polymer compositions to boast transition temperatures within a range of applicable temperature for thermal shape memory