Preparation Of Graft Copolymers Based On Hyperbranched Polyglycerol

The designing and synthesis of copolymer with complex architecture are always drew much attentions of polymer chemists in past decades. Because of the development of "living"/controlled polymerization technologies, a variety of linear and nonlinear (such as comb-shaped, star-shaped, dendritic,hyperbranched) copolymers have been synthesized and tailored.These special copolymers show quite different morphologies in bulk and self-assembly behaviors in solution, which make them great potential applications in chemistry, materials,physics and biology. But it is still a huge challenge of how to synthesize the three-dimensional graft polymer. Because of the limitation of single polymerization methodology and purification of the products, there are few publications about the three-dimensional graft copolymers. Thus, it is a very significative work to explore a novel synthesis method for these copolymers with complicated three-dimensional structures.In this thesis, a novel kind of graft copolymers with three-dimensional structure is synthesized by the combination of "living"/controlled polymerization (ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer polymerization (RAFT)) and "Click" Chemistry. Our work provided an effective way for the synthesis of three-dimensional graft copolymers.The final products are characterized by 1H NMR, GPC and FT-IR etc.in detail.The essential results obtained are shown as follows:1.The well-defined hyperbranched polyglycerol (HPG) was synthesized by ROP of glycerol using 1,1,1-trihydroxymethyl propane and methanol potassium as initiator. After esterified with 2-bromoisobutyryl bromide by different proportion, a series macroinitiators HPG-g-Br were obtained and then initiated the ATRP of styrene (St) for graft copolymers HPG-g-PS-Br. The HPG-g-PS-N3 was then produced by azidation of HPG-g-PS-Br. 2.The (3-[(1'-Ethoxyethyl)-ethoxyethyl]-1,2-propanediol (EEPD) containing two active and one protected hydroxyl groups was obtained by the ring opening reaction of ethoxyethyl glycidyl ether (EEGE).The EEPD and diphenylmethyl potassium (DPMK) was used as co-initiator to initiate ROP of ethylene oxide (EO) to produce "V" shaped PEO. After end-capping reaction, deprotection and alkyne group modification, the PEO2-alkyne chain with an alkyne group in the middle was obtained.3.The obtained polymer HPG-g-PS-N3 was reacted with PEO2-alkyne via "Click" chemistry in the presence of CuBr/PMDETA in DMF, and then the graft copolymers HPG-g-(PS-b-PEO2) with "Y" shaped side chain was obtained.By detachment of PS-b-PEO2 side chains from the HPG core,the reliable structure and molecular weight of graft copolymers was well characterized.4. The hydroxyl groups of the HPG were also modified to chain transfer agent trithiocarbonate groups HPG-TTC for RAFT polymerization of NIPAM. The graft copolymer HPG-g-PNIPAM shows the Lower Critical Solution Temperature (LCST), and the relationship between the LCST and structure was studied.