Synthesis Of Dual Thermo-and Ph-sensitive Network-grafted Hydrogels As Drug Delivery System

Intelligent hydrogels, among stimulus-response hydrophilic polymer materials, are of interest in drug delivery system. Recently, due to the research development of multi-sensitive and quick-responsive polymer hydrogels, the application of intelligent hydrogels is a hot topic. Based on the research of the precursors, this dissertation describes the synthesis and application of the dual thermo-and pH-sensitive network-grafted hydrogels. The main results of this thesis are listed as follow:1. Dual thermo- and pH-sensitive network-grafted hydrogels made of poly(N, N-dimethylaminoethyl methacrylate) (PDMAEMA) network and poly(N-isopropylacrylamide) (PNIPAM) grafting chains, the opposite as well, were successfully synthesized by the combination of atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) polymerization and click chemistry. PNIPAM or PDMAEMA having two azide groups at one chain end was prepared with an azide-capped ATRP initiator. Alkyne-pending poly(N,N-dimethylaminoethyl methacrylate-co-propargyl acrylate) [P(DMAEMA-co-ProA)] or poly(N-isopropylacrylamide-co-propargyl acrylate ) [P(NIPAM-co-ProA)] was obtained through RAFT copolymerization using dibenzyltrithiocarbonate as chain transfer agent. The subsequent click reaction led to the formation of the network-grafted hydrogels. The dual stimulus-sensitive hydrogels exhibited fast response, high swelling ratio and reproducible swelling/deswelling cycles under different temperatures and pH values.2. By interchanging the network chain and graft chain and varying the composition of precursors, the influences of degree of crosslinking, graft chain length as well as chain architecture of network-grafted hydrogels on the properties of the hydrogels were investigated in terms of morphology and swelling/deswelling kinetics. The influences of temperature and pH on swelling/deswelling behavior, were also studied.3. The uptake and release of ceftriaxone sodium by PDMAEMA-g-PNIPAM hydrogels, showed both thermal and pH dependence, suggesting the feasibility of these hydrogels as thermo- and pH-dependent drug release devices.