Synthesis Of Heteroarm Star-shaped Copolymers Based On PEO

Controlled/"living" polymerization technology continues to develop, allowing people to design and synthesize a variety of structures of new copolymers (comb-shaped, star, dendritic, etc.).The copolymers have special structures, and can be used in chemistry, physics, biology and pharmaceutical sectors. Polyethylene oxide (PEO) both soluble in water can also dissolve in most organic solvents, but also has good biocompatibility. PEO with other polymer chains coupled together, can have its features to be transferred to the entire copolymer, so it become the research hotspot in recent years. In this paper, based on PEO a series of A2B2 type and A2B2C2D2 type heteroarm star-shaped copolymers were synthesized, and characterized their structures.The main task of this article:1.By anionic ring-opening polymerization(AROP) techniques, protected two hydroxyl pentaerythritol and diphenyl methyl potassium (DPMK) as initiator agent were used to synthesize two arms of PEO2.As hydroxyl ends of the PEO2 would affect the synthesis of the next block, so we had to close them.Benzyl bromide was used to react with the end of hydroxy-terminated. First, The protection hydroxy-terminated was deprotected in acidic solution, so that the original protection two hydroxyl of pentaerythritol can be deprotected. Second,3-benzyl-3 thio-carbonate-propionic acid (BSPA) was condensed with the deprotected PEO2 to obtain macromolecular chain transfer agent (PEO-BSPA)2. Third, (PEO-BSPA)2 was used to initiate 2-(dimethylamino) ethyl methacrylate (DMAEMA) polymerization by RAFT. PEO2-b-PDMAEMA2 was obtained, and studied its reaction kinetics to determine the controllability of the reaction. These polymers'structure, molecular weight and molecular weight distribution were character By NMR and GPG.The results prove that the polymers have clear structure, narrow molecular weight distribution and molecular weight controlled.2.ATRP macroinitiator (PEO-Br)2 had been synthesized by the esterification reaction of PEO2 with dibromo-isobutyryl bromide. First, under acidic conditions, the protection of two hydroxyl pentaerythritol were decompressed,and synthesized heteroarm copolymer PEO2-b-PS2 by ATRP reaction. Second, with the solution out of two hydroxyl protection, through the coordination ring-opening polymerization(CROP), the polycaprolactone (PCL) block was synthesized Heteroarm copolymer PCL2-b-PEO2-b-PS2 was obtained. Second, PCL hydroxyl end of the refine to make it with the reaction of macromolecular chain transfer agent BSPA obtained macromolecular RAFT chain transfer agent. It was used to initiate methacrylate monomer 2-(dimethylamino) ethyl methacrylate (DMAEMA) polymerization to obtain a new type of heteroarm copolymer PDMAEMA2-b-PCL2-b-PEO2-b-PS2.By nuclear magnetic resonance spectroscopy, infrared spectroscopy and GPC, structure of the new heteroarm copolymers and molecular weight were proofed, and molecular weight distribution were very narrow. And reaction kinetics studies show that molecular weight increases linearly with the conversion rate, that is consistent with the characteristics of living polymerization.