A new approach for synthesis of cyclic poly (N-isopropylacrylamide), for applying in biomaterial applications

Abstract

This research reports the successful synthesis of the cyclic poly (N-isopropyl acrylamide) (cPNIPAAM) by a new method. For this purpose, α, ω-difunctionalized precursor was synthesized, applying a free radical polymerization process in the methanol solvent, and using the nitroxide component, hydroxy-TEMPO, as the terminator for the first time. Then, end-to-end equilibrium, with an appropriate coupling agent was utilized for cyclization reaction in the two solvents of water and dimethylforamide (DMF). Using a terminator to produce functionalized chains led to controlled molecular weight polymers. As a result, reduced molecular weight precursors were created, resulting in smaller rings with improved water solubility, LCST temperature and more environmentally compatible friendly products, particularly in medicinal objectives. In compared to previous techniques, these characteristics represent the precise innovation of our study. The yield and optimum polymerization conditions were provided. The polymer products were characterized by FTIR, 1HNMR, GPS, TLC, DSC, DLS and viscometry methods. The morphology and molecular weight were compared with the previously produced polymers. The results confirmed the formation of polymers with lower molecular weight compared to previous methods. Despite its lower cyclization yield, water was a better solvent compared to DMF.