Synthesis Of Thermo-Responsive Polymers With Both Tunable UCST And LCST

The research on the polymers with thermo-responsive behavior is one hot topic in recent years. The well-defined thermo-responsive polymers could be easily synthesized via the reversible addition-fragmentation chain transfer polymerization. The totally hydrophilic thermo-responsive polymer and zwitterionic polymer have the potential to be used in the biomedical field due to their excellent biocompatibility. Based on the research of precursors, this master thesis describes the synthesis of thermo-responsive polymer with both tunable UCST and LCST. The main results of this thesis are as follows:1. Well-defined random copolymer with lower critical solution temperature (LCST) of poly[2-(2-methoxyethoxy)ethyl ethacrylate-co-oligo(ethylene glycol) methacrylate], [poly(OEGMA-co-MEO₂MA)] was prepared via reversible addition-fragmentation chain transfer polymerization. The LCST of random copolymer was tunable by changing the feed molar ratio. The structure, molecular weight and distribution of polymer were characterized by 1H nuclear magnetic resonance and gel permeation chromatograph (GPC). The thermo-responsive behavior of random copolymer was studied by temperature-dependent turbidity measurement. The LCST values increased with increasing OEGMA feed molar ratio. Moreover, the correlation between the observed LCST and the feed molar ratio of OEGMA was found to be simple.2. The block copolymer of poly{N-[3-(dimethylamino)propyl] methacrylamide}-b- poly[2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol) methacrylate], poly(DMAPMA)-b-poly(OEGMA-co-MEO₂MA) was prepared by using the poly(OEGMA-co-MEO₂MA) as macro-chain transfer agent (macro-CTA). Similarly, the structure, molecular weight and distribution of polymer were characterized by 1H nuclear magnetic resonance (NMR) and gel permeation chromatograph (GPC). Because of containing copolymer, quaternization by adding 1,3-propanesultone changed tertiary amine block into zwitterionic block . The zwitterionic polymer displayed UCST behavior due to electrostatic interaction. The UCST behavior of zwitterionic polymer was researched by dynamic laser light scattering and temperature-dependent turbidity measurement. The results shoe that the UCST values increased with increasing the degree of quaternization (DQ). In the intermediate temperature range, that is, above the UCST and below the LCST, copolymers were observed to exist as soluble unimers in water, the hydrodynamic diameter was below 10 nm. But beyond this range, copolymers precipitated as collapsed associations in water, the hydrodynamic diameter was about 100 nm.