Itaconic acid, a naturally occurring compound mass-produced via fermentation of glucose, was reacted with ethanolamine or ethylene diamine to afford hydroxy-acid or diacid monomers containing the 2-pyrrolidone lactam. Homopolymerization or copolymerization with diols, respectively, yielded polylactam esters with higher glass transition temperatures and faster hydrolytic degradation compared to the commercial polyester polylactic acid (PLA).
Concurrent ring-opening polymerization/polycondensation of lactones and bioaromatic hydroxy-acids yields random copolymers with improved and controlled thermal properties.
Ferulic acid and p-coumaric acid are abundant, biorenewable precursors for the synthesis of polyethylene ferulate (PEF) and polyethylene coumarate (PEC), as well as cognate copolymers with prescribed hydrogenation of the main-chain double bond. By controlling the comonomer feed ratios, copolymers with tunable thermal properties are obtained, including the thermal range occupied by polystyrene (PS). † Electronic supplementary information (ESI) available: Synthetic details, complete polymer characterization data, and method to determine copolymer composition. See
Macroporous photonic crystals with optically bistable states have been fabricated by using thermoresponsive shape memory polymers. The reversible transition between an ordered permanent state and a disordered temporary state results in tremendous changes in the appearance and the optical properties of the membranes.
This study reports unconventional, all-room-temperature shape memory (SM) effects using templated macroporous shape memory polymer (SMP) photonic crystals comprising a glassy copolymer with high-glass transition temperature. "Cold" programming of permanent periodic structures into temporary disordered configurations can be achieved by slowly evaporating various swelling solvents (e.g., ethanol) imbibed in the interconnecting macropores. The deformed macropores can be instantaneously recovered to the permanent geometry by exposing it to vapors and liquids of swelling solvents. By contrast, nonswelling solvents (e.g., hexane) cannot trigger "cold" programming and SM recovery. Extensive experimental and theoretical investigations reveal that the dynamics of swelling-induced plasticizing effects caused by fast diffusion of solvent molecules into the walls of macropores with nanoscopic thickness dominate both "cold" programming and recovery processes. Importantly, the striking color changes associated with the reversible SM transitions enable novel chromogenic sensors for selectively detecting trace amounts of swelling analytes mixed in nonswelling solvents. Using ethanol-hexane solutions as proof-of-concept mixtures, the ethanol detection limit of 150 ppm has been demonstrated. Besides reusable sensors, which can find important applications in environmental monitoring and petroleum process/product control, the programmable SMP photonic crystals possessing high mechanical strengths and all-room-temperature processability can provide vast opportunities in developing reconfigurable/rewritable nanooptical devices.
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