Synthesis Of A New Family Of Thermo-responsive Polymers Based On Poly[N-(4-vinylbenzyl)-N,N-dialkyamine] And The Application

Thermo-responsive polymers represent an important class of stimuli-responsive materials, which receive significant attention both in polymer science and in practical application. The polymers bearing the amide group form the largest group of thermo-sensitive polymers. Compared with millions of the general polymers showing neither LCST nor UCST, the thermo-responsive polymers are very limited, In this study, a new family of thermo-responsive polymers based on poly[N-(4-vinylbenzyl)-N,N-dialkylamine] are synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, and their thermo-response upon heating or cooling in the alcohol/water mixture and in acetone is introduced. Then, corona-shell-core nanop articles of the temperature-sensitive triblock copolymer were prepared by seeeded dispersion polymerization, and the reversible nanoparticle-to-vesicle transition of the triblock copolymer is investigated. The content of this dissertation involves the following three aspects:1. Synthesis and property study of a new family of the thermo-responsive polymers based on poly[N-(4-vinylbenzyl)-N,N-dialkylamine]In this section, a new family of the thermo-responsive polymers based on poly[N-(4-vinylbenzyl)-N,N-dialkylamine] with the pendent amine group were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. These polymers showed the LCST and/or the UCST in alcohol and in the alcohol/water mixture. The polymer molecular weight, the polymer concentration, the cosolvent/nonsolvent and the deuterated solvent affecting the LCST and/or UCST were investigated, and their great influence on the LCST/UCST was demonstrated. The origin of the phase transition of poly[N-(4-vinylbenzyl)-N,N-dialkylamine] at LCST upon heating was investigated and the possible reason was proposed. The proposed polymers based on poly[N-(4-vinylbenzyl)-N,N-dialkylamine] are anticipated to broaden the thermo-responsive polymer range and will be useful in polymer science. 2. Seeded dispersion RAFT polymerization of thermo-responsive corona-shell-core triblock copolymer nanoparticlesIn this section, a new kind of heterogeneous RAFT polymerization called seeded dispersion RAFT polymerization to prepare triblock copolymer corona-shell-core nanoparticles of the temperature-sensitive PDMA-b-PS-b-PVEA is proposed. Well-controlled seeded dispersion RAFT polymerization as indicated by the pseudo-first-order kinetics, the linear increase in the triblock copolymer molecular weight with the monomer conversion and the narrow molecular weight distribution of the synthesized triblock copolymer was performed, and triblock copolymer corona-shell-core nanoparticles, in which the temperature-sensitive PVEA block forms the core, the solvophobic PS block forms the shell, and the solvophilic PDMA block forms the corona, were prepared.3. Temperature induced nanoparticle-to-vesicle transition of triblock copolymer corona-shell-core nanoparticlesIn this section, the reversible nanoparticle-to-vesicle transition of the triblock copolymer is investigated. When the corona-shell-core nanoparticles were dispersed in alcoholic solvent at temperature below the lower critical solution temperature (LCST) of the core-forming PVEA block, the nanoparticle-to-vesicle transition occurred, and the unsymmetrical ABC triblock copolymer vesicles were formed. The nanoparticle-to-vesicle transition is ascribed to the initial nanoparticle swelling in the alcoholic solvent and the subsequent out-migration of the core-forming PVEA block from the core layer to corona, which was confirmed by the real-time1H NMR analysis and XPS analysis. The parameters affecting the nanoparticle-to-vesicle transition were investigated, and it was found that the nanoparticle-to-vesicle transition took place in the alcoholic solvent at temperature below LCST when the triblock copolymer containing a long core-forming PVEA block.