Aqueous Radical Addition-Coupling Polymerization For The Synthesis Of Hydrophilic Periodic Polymer

Control on the molecular weight and unit sequence is two key issues in controlled polymer synthesis. Radical addition-coupling polymerization (RACP) is a kind of rapid and efficient reaction which has been proposed for synthesis of polymer with specific structures, such as periodic polymer, block copolymer, macrocyclic polymer and so on. In this dissertation, We performed RACP in aqueous media to synthesize well-controlled hydrophilic periodic polymers with a regular unit sequence [ABxAC]n from water-soluble monomers, which was not applicable by conventional condensation polymerization.Water-soluble dibromo monomers (Br-PEG600-Br, Br-PEG1000-Br, Br-PEG2000-Br) were prepared by reaction of a-bromo isobutyryl bromide with α,ω-dihydroxyl poly(ethylene glycol). N-(2-hydroxyl ethoxyethyl) 2-pyridyl methanimine (HEEPMI) and N-(2-hydroxyl ethoxyethyl)-bis(2-picolyl) amine (HEEBPA) were synthesized, both of them were water-soluble due to the hydroxy group.Me-β-CD is able to host nitrosobenzene (NB) and form water-soluble host-guest complex (Me-β-CD/NB) due to its hydrophobic cavity and hydrophilic exterior. Me-β-CD/NB was reacted with Br-PEG-Br by aqueous RACP promoted by different initiation systems, and Cu/HEEPMI was proved to be the best initiator, which could give polymer with the highest DP (17) and narrow molecular-weight distribution (2.08). Finally, Me-β-CD was removed from the crude polymer by dialysis to obtained pure hydrophilic polymer. The polymer has repeating sequence of [ABxAC]n which is evidenced by NMR analysis and thermal degradation.2-methyl-2-nitrosopropyl-2-hydroxyacetate (MNPHA) with hydroxyl group was synthesized. When MNPHA was reacted with Br-PEG-Br by aqueous RACP promoted by different initiation systems, the results showed that Cu/HEEPMI was the best initiator, which could give polymer with the highest DP (24) at appropriate condition (50 ℃,0.05 M), and the conversions were more than 97% for all the polymerizations. This method could not only produce themodegraded hydrophilic periodic polymer directly, but also introduce hydroxyl group into the main chain of polymer, which could be further modified.Aqueous radical addition-coupling polymerization has been realized by above two approaches and hydrophilic periodic polymer possessing [ABxAC]n (A=ester, B=ethylene oxide, C=N-O) repeating sequence was synthesized.