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

This research reports the successful synthesis of the cyclic poly(N-isopropyl acrylamide) (cPNIPAAM) by a new method. For this purpose, alpha\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document}, omega-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 dimethylformamide (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 comparison with 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, (HNMR)-H-1, 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.

Automated summary

This study successfully synthesized cyclic poly(N-isopropyl acrylamide) (cPNIPAAM) using a new method. The synthesis involved the generation of an alpha\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document}, omega-difunctionalized precursor through a free radical polymerization process with methanol solvent and the use of hydroxy-TEMPO as the terminator. The cyclization reaction was achieved through end-to-end equilibrium using a suitable coupling agent in water and dimethylformamide (DMF) solvents. The use of a terminator resulted in controlled molecular weight polymers, leading to smaller rings with improved water solubility and LCST temperature, making them ideal for medicinal purposes. The study also compared the morphology and molecular weight of the synthesized polymers with previous techniques, confirming the formation of polymers with lower molecular weight and higher solubility in water compared to DMF.