Preparation And Temperature-responsive Performances Of NIPAM-ionic Liquid Copolymers

Temperature-sensitive polymers are a type of stimulus-responsive polymer that can adjust the structure and give feedback when the temperature changes.Because it is easy to adjust the structure and performance of the polymer by changing the temperature,this type of polymer has become the most concerned,one of the most intensively researched stimulus responsive polymers.Among them,poly-N-isopropylacrylamide(PNIPAM)is a typical representative of temperature-responsive polymers.Copolymerization of NIPAM with other monomers is an effective way to adjust the temperature responsiveness of PNIPAM,and ionic comonomers can exhibit unique temperature responsiveness with NIPAM copolymers due to their ionic effect in the solution.In this study,a linear copolymer of NIPAM and imidazole-based ionic liquids was prepared by the reversible addition-fragmentation transfer polymerization(RAFT)method,and the copolymer was analyzed by infrared spectroscopy,hydrogen nuclear magnetic spectroscopy,thermogravimetry and gel permeation chromatography.Its chemical structure,thermal stability and molecular weight were characterized.The temperature sensitivity and response mechanism of the copolymer were studied by dynamic light scattering and rheological methods.The specific research content is as follows:(1)The block copolymer PNIPAM-b-PVBIm-Br was prepared by the RAFT polymerization method.The particle size of the polymer chain in the aqueous solution was observed by the dynamic light scattering method,and the polymer aqueous solution was studied by the rheological method.Rheological properties,the temperature sensitivity and response mechanism of block copolymers were studied.It was found that after the ionic liquid 1-vinyl-3-butylimidazolium bromide([VBIm] Br)was introduced into the NIPAM system,the size of the association formed by the block copolymer chain in the aqueous solution was larger,and its response temperature and response rate were increased,the hysteresis in the reversible process was improved.(2)Block copolymers with different monomer content and different anions were prepared by RAFT polymerization method.The effects of monomer content and anion on the temperature sensitivity and rheological properties of block copolymers were studied by dynamic light scattering and rheological research methods.The results showed that the increase of NIPAM monomer content could increase the LCST;when the ionic liquid monomer content changes less,the effect on LCST was small;the anion mainly affects the size of the copolymer chain association in the aqueous solution.(3)The random copolymer PNIPAM-co-PVBIm-Br was prepared by the RAFT polymerization method.The particle size of the polymer chain in the aqueous solution was observed by the dynamic light scattering method,and the polymer aqueous solution was studied by the rheological method.Rheological properties,the temperature sensitivity and response mechanism of random copolymers were studied.It was found that the random copolymer aqueous solution had a sol-gel change in the rheological test,a wide adjustable range of response temperature,and obvious hysteresis in the reversible process.