Study On Synthesis And Morphology Of Amphiphilic Copolymers

Amphiphilic polymers are useful materials, which are composed of both hydrophobic and hydrophilic segments. It has been successfully applied in many fields such as drug delivery, surfactant, coating and nanotechnology, and so forth. Particularly, phase separation of amphiphilic copolymers has received increasing attention due to their ability to spontaneously form periodic morphologies. Our research focus is to synthesize copolymer with gyroid structure, because of his special microstructure and physicochemical properties. In this thesis, amphiphilic copolymers, such as PS-PNIPAM copolymers, polyether block copolymers and dextran copolymers with polyether as side chains, were prepared by RAFT and AROP. And the morphology of the copolymers was studied by many means. The details are as follows:(1) Diblock copolymers PS-b-PNIPAM were synthesized by RAFT. The structure and morphology of block copolymers were characterized by means of 1H-NMR, infrared spectroscopy, GPC and TEM. The experiment results implied that the morphology of PS-b-PNIPAM copolymers is closely related to block structure, The mass ratio of St to NIP AM was 0.38,1.49 and 0.60 respectively forming spherical, lamellar and gyroid morphology. Water and oil absorption of copolymer with gyroid structure was higher than others. And the dynamic contact angle results further indicated that copolymer with gyroid structure had good hydrophilic and hydrophobic performance(2) The polymerization of alkylene oxide was carried out through anionic ring-opening polymerization using potassium tert-butoxide as initiator. The results of polymerization conversion and GPC analysis indicated that the rate of the reaction increased in the presence of catalyst and the polymer had a clear structure with controllable molecular weight and narrow distribution. Therefore the anionic ring-opening polymerization of alkylene oxide is a living process in the catalyst system. The catalyst effect of PEG is similar to crown. Triblock copolymer PSTO-PEG-PSTO, PBO-PEG-PBO and PPGE-PEG-PPGE were synthesized by AROP, using KO-PEG-OK as macroinitiator.(3) Graft modified dextran amphiphilic copolymer were synthesized by ring-opening polymerizaition using dextran potassium alcoholate as initiator and STO (or PGE) as monomer. Good hydrophilic and hydrophobic performance of these graft copolymers (31wt%-78wt% dextran unit) were verified by the dynamic contact angle and swelling behavior. Meanwhile both water and oil absorption of graft copolymers films increased with the increasing of the hydrophilic dextran segment, suggesting formation of gyroid morphology in the copolymer films. In addition, Dextran-g-PPGE has good protein adsorption resistance.(4) IR spectrum was initially recorded to measure the composition of PS-b-PNIPAM block copolymers. It was found that the composition calculated based on the IR spectra of the copolymers was quite different from that obtained by 1H-NMR measurement. Transmission IR spectra of block and graft copolymers showed blue and red shift. From this discovery, we researched the relation between the peak intensity in IR spectrum of copolymers and its phase separation morphology. The MATLAB technique was used to calculate the interfacial length (L) in a TEM image of phase separated copolymer. Then the L value was linked with the shift degree of IR characteristic peaks. It was found that the intensity of the shifted peak incread with the increasing of the interfacial length. Therefore, infrared spectroscopy could be used as a means to predict the phase separation morphology of amphiphilic copolymer in real time.