Preparation Of Stimuli-Responsive Polymers And Functional Polyolefins Via RAFT Polymerization

Stimuli-responsive polymers and functional polyolefins are one of extraordinary active fields of polymer chemistry. In recent years, the development of controlled/living polymerization has made it possible that a large number of monomers can be synthesized in controlled manner and a diverse range of stimuli-responsive polymers and functional polyolefins have been prepared via reversible addition-fragmentation chain transfer polymerization. The dissertation includes following four parts:1 . Stimuli-responsive hyperbranched polymers were synthesized via RAFT polymerizaiton in one pot, corresponding hydrogels formed simply by adding water into the above systems. The produced PEG-based polymers are temperature-sensitive,and they became less soluble in water and aggregated into nanoparticles when heated above the LCST. Subseqently, the disulfide exchanges inside nanoparticles ocuured to crosslink the nanoparticles into nanogels. The resulting hydrogels particles are temperature-, photo-, and redox-responsive.2. Disulfide-contained PEG-based hyperbranched polymer was prepared via RAFT polymerization. Temperature-responsiveness and self-crosslinking property were investigated. Then, the PEG-coated silica nanoparticles were obtained simply by heating the silica nanoparticles aqeous dispersion system and controlling pH,temperature, polymer concentration and continuous drip-injection. Corresponding PEG-based hollow and bioreducible nanocapsules formed by etching the silica core.3. Propylene sulfide/N-isopropylmethacrylamide copolymer [P(PS-co-NIPMAM)]and propylene sulfide/N,N-dimethylacrylamide copolymer [P(PS-co-DMA)] were prepared via the combination of anionic ring-opening reaction(ROP) and RAFT polymerization in one-pot reaction, in which S-1-dodecyl-S'-(?,?'-dimethyl-?,?-acetic acid) trithicarbonate not only acted as chain transfer agent of RAFT polymerization but also an initiator of ROP. Due to the hydrophobicity of PPS segment,P(PS-co-NIPMAM) can self-assemble into micelles in water at room temperature.When exposed to ROS, P(PS-co-NIPMAM) micelles disassembled because PPS chain was oxidixed into poly(propylene sulphone)(PPP) and became water-soluble.Moreover, the new micelles formed when heating solution to above LCST of PNIPMAM. Therefore, the kind of copolymer has potential applications for control release of drugs.4. A series of functional polyethylenes were successfully prepared via RAFT copolymerization of ethylene and fuctional vinyl monomers under mild conditions(T=70 ?, P<30 bars). This method not only obtained high molecular weight polymers(Mn> 10000 g/mol, PDI<1.3) with narrow molecular weight distribution, but also,could control the incorporation ratio of the polar monomer, which expands the way of synthesis of functional polyolefins.