The Synthesis,Separation And Application Of Thermo-responsive Star Polymers

Stimuli-responsive polymers are the kind of polymers reacted to corresponding stimuli of external environment,and have a broad application prospect in the fields of diagnosis,drug delivery and coatings.Thermo-responsive polymers are the most widely used and the most easily obtained ones,which has the basic characteristics of clean,pollution-free and sustainable.There are two main types of thermo-responsive polymers:upper/lower critical solution temperature(UCST and LOST).Two types of monomers were selected in this study:zwitterionic monomer 3-(2methacryloyloxyethyl dimethylamine)propyl sulfonate(DMAPS)and monomer Di(ethylene glycol)methyl ether methacrylate(MEO2MA).Two series of star polymers were synthesized by RAFT polymerization,and the"Arm-first" method.Using the difference of responsive temperature between star and linear polymers,we successfully obtained the pure star polymer with narrow molecular weight distribution by using centrifugal method creatively.Moreover,the thermo-responsive sensitivity of the polymers were greatly improved after centrifugation.The purpose of this study is to provide an efficient method for the purification of star polymers and other complicated topological stimuli-responsive polymers.Obtaining the high thermo-responsive sensitivity zwitterionic star and linear polymers with the natural advantages in polymer chain end-segment via the method of RAFT polymerization,and using the gold nanoparticles(AuNPs)which trends to absorbed polymers with the thiol group,we successfully got the thermo-responsive composite nanoparticles by grafting the thermo-responsive polymers on AuNPs.The aim is to make use of the high efficiency of "extinction rate to light" of gold nanoparticles.With external light source,gold nanoparticles will absorb light and generate heat,which is transferred to the thermo-sensitive polymers,to control the chain state of the thermo-sensitive polymer.It is expected to be applied in the fields of drug carrier to improve the accuracy of targeted drug release,or apply it to molecular motors with the high efficiency of transferring the optical energy to kinetic energy.