Molecular Design And Self-Assembly Of CO₂-Based Smart Aliphatic Poly (Urethane-amine)s

CO2 is a renewable synthetic feedstock since it is abundant, nonflammable, and a waste product of many chemical processes. The copolymerization of aziridine derivates and CO2 proceeded under supercritical conditions to give a series of aliphatic poly(urethane-amine)s. The aziridine derivates with different substituent were prepared from amino acids via reduction reaction and Wenker synthesis. An aqueous solution of the copolymer underwent a temperature and pH induced phase transition at a LCST. The effects of substituent and Salen-metal catalysts on the copolymerization and LCST have been studied. The urethane content and the tacticity could be regulated by utilizing diverse Salen-metal catalysts. The poly(urethane-amine) catalyzed by Salen-Zn complex, which had a LCST of 45℃in water with 5℃hysteresis between heating and cooling cycles, was obtained. A kind of novel biodegradable smart materials based on renewable resources CO2 and amino acids were produced by utilizing supercritical CO2 and Salen-metal catalysts.On the other hand, there has been a great deal of research activity in the development of smart hybrid materials, especially in those of pH or temperature responsive hybrid materials. CaCO3/alginate/polyurethane hybrid beads with pH-and thermo- responsive drug release properties were prepared using supercritical carbon dioxide. Novel temperature responsive aliphatic poly(urethane-amine)s were employed as thermal composition. The formation of CaCCO3 in the alginate beads was clearly identified through scanning electron microscopy (SEM) and Thermogravimetric Analyzer (TGA). Drug release behaviors using indomethacin as a model drug were found to be pH-and thermo- responsive. The resulting alginate beads could be used as smart hybrid material for sustained dual-responsive drug delivery.