Synthesis and rheological analyzes of temperature and light sensitive gels comprising amphiphilic azobenzene polymers, chitosan and pluronic F127

Abstract

This study investigates the reinforcement of pluronic (PF127) based temperature responsive hydrogels with photosensitive functionalities to create smart and injectable materials. For this purpose, 4-[4-[(4-phenyl)azo]phenoxy] methacrylate (PAzPMA) was synthesized and further polymerized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The structures of the copolymers were characterized by several techniques such as Fourier-transform infrared (FT-IR), nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The azobenzene-functionalized copolymer was combined with P127 solid polymer in micelle form and with P127 micelles in solid form to obtain PF127-AzoMx and PF127-AzoPx gels, respectively. When the temperature profiles of the PF127-AzoMx and PF127-AzoPx systems were compared with PF127, sol-gel phase transition were shifted to lower temperatures due to stronger hydrophobic interactions. Additionally, different concentrations of N,N,N-trimethyl chitosan (f-chitosan) were added to the gel systems and their rheological properties were investigated by exposing them to UV light. It has been observed that the presence and concentration of f-chitosan are important for the variation of the interactions\" strength between the micelles. The study highlights the potential of multifunctional hydrogels for specific biomedical applications that combine sensitivity to both thermal and optical stimuli for controlled drug delivery and tissue engineering purposes.