Synthesis Of Hyperbranched Polymers By Chemoenzymatic And Its Self-assembly Behavior Study

Generally, dendrimers have a three-dimension structure, of which the molecule displays the character of symmetry and tightness, as well as the special physical and chemical character. Thereby, much attention is paid to the synthesis and application of dendrimers. However, the hyperbranched aliphatic polyesters synthesized by enzymatic ring-opening technique have a shortage of low molecular weight, which couldn't present the characteristic of polyester. Hence, enzymatic ring-opening polymerization and chemistry technique were combined to synthesize hyperbranched copolymers with functional groups in the study.Enzyme is a kind of protein that produced by living cells and with the character of catalyze and living/control. It is often used as biologic catalyst. Enzymatic catalyzed polymerization is a kind of reaction that catalyzed by enzyme. So far, the control of reaction condition and the optimization and selection of enzyme still need to be investigated in the further study. However, as a new polymerization technique, enzymatic catalyzed polymerization provides a new and friendly-condition way for the synthesis of macromolecule. It can be widely used in medicine, environmental protection and national defence. Sunny Skaria et al used Novozyme435-catalyzed ring-opening (ROP) polymerization of BHB (2,2-bis(hydroxymethyl) butyric acid at 85℃in an oil bath .They obtained different DB of hyperbranched aliphatic polyesters.As a living/controlled method of polymerization, ATRP is attractive for its characteristics of low polydispersity and controlled molecular weight. ATRP is applied to the most of (meth) acrylate and styrene monomers because of its gentle reaction condition. Therefore it is suitable for designing and synthesizing the functional materials. So we use ATRP and enzymatic ring-opening polymerization technique together to synthesize the functional materials with special characteristics.Based on the above reasons, we combined enzymaticpolymerization and ATRP to synthesize several new functional hyperbranched polymers.In Chapter two,the hyperbranched aliphatic polyester P(ε-CL)was synthesiszed by means of Novozyme435-catalyzed ring-opening (ROP) polymerization of BHB (2,2-bis(hydroxymethyl) butyric acid. Analyses by 1H NMR,13C NMR,WAXD,DSC,POM,IR. In the DSC curves, with increasing the length of PCL, the crystallization and melting temperature of PCL block increased significantly. The isothermal melt-crystallization at 25 oC of hyperbranched polymers was observed by POM. The growth rate of the hyperbranched polymers spherulites decreased sharply with decreasing the length of PCL.In chapter three, The chains ended with hydroxyl of P(ε-CL)were modified by the esterification ofα-bromopropionyl bromide to obtain hyperbrancheds difunctional macroinitiator, which was used in the ATRP of St. CuCl/HMTETA was used as the catalyst system in the reaction of ATRP to acquire the hyperbranched copolymers polystyrene-block-poly (2,2-bis(hydroxymethyl) butyric acid). The PSt structure determined by 1H,GPC. The self-assembly of the hyperbranched polymers into aggregation micelles in aqueous media was determined by Spectrofluorometer,SEM,TEM,AFM,DLS,XRD, AFM. The hyperbranched polymers have lots of promising applications in advanced biotechnology, such as DNA separation, targeted drug delivery, enzyme immobilization, and immunological assay.In chapter four, a novel method for the synthesis of hyperbranched PMMA and PGMA were developed by combining ROP and ATRP. Both polymers structure were determined by 1H and GPC. The critical association concentrations (CAC) were determined by pyrene monomer fluorescence probe technology. The self-assembly of the hyperbranched polymers were determined by SEM,TEM,AFM,DLS. Hyperbranched polymers have shown to exhibite the different properties from those of the linear analogues, such as low viscosity, high solubility. And the hyperbranched polymers have a multiplicity of using range from adhesive improvers and viscosity modifiers to applications in coating, rheology controlagents pharmaceuticals, and so on.