Synthesis and characterization of graft copolymer hydrogel by “grafting from” atom transfer radical polymerization using brominated macro monomeric initiator and investigation of hydrogel properties

Abstract

In this study, poly(ɛ-caprolactone-g-2-hydroxy ethyl methacrylate) [P(CL-g-HEMA)] graft copolymer hydrogels were successfully synthesized through multi-step reactions. For this purpose, firstly, hydroxyl-terminated poly(ɛ-caprolactone) (PCL-OH) was obtained by ring-opening polymerization (ROP) method of ɛ-caprolactone using 3-chlor-1,2-propanediol initiator, which is suitable for ring-opening polymerization method. Then, from the reaction of synthesized PCL-OH and 3-bromopropionyl chloride, a new brominated poly(ɛ-caprolactone) (PCL-Br) was synthesized for use as a functionalized atom transfer radical polymerization (ATRP) initiator. Poly(ɛ-caprolactone-g-2-hydroxy ethyl methacrylate) [P(CL-g-HEMA)] graft copolymer hydrogels were synthesized by “grafting from” atom transfer radical polymerization (ATRP) of 2-hydroxy ethyl methacrylate (HEMA) presence the new synthesized functionalized ATRP initiator (PCL-Br) and hydrogel properties were investigated. The synthesized functionalized initiators and graft copolymer hydrogel were characterized by spectroscopic methods such as 1H-NMR, FT-IR, TGA, DSC and SEM. The observation of two different decomposition temperatures, respectively, from the TGA analysis results may support the formation of the biblock graft copolymer. A glass transition temperature (Tg) of the graft copolymer hydrogel was found by DSC, and this value is between the Tg values of the homopolymers forming the graft copolymer hydrogel. Water swelling values of graft copolymer hydrogels were measured and calculated every 24 h in pure water with pH = 7 at from + 4 to 65 °C. Considering the weight of dry graft copolymer hydrogels, it was seen that water was absorbed at most at + 4 °C. As the temperature increased, the water absorption or swelling of the hydrogel decreased.