Studies Of Novel Functional Polymers Combination Of Enzymatic Polymerization And ATRP

Enzymes have traditionally been used in biochemical studies, molecular biology and related scientific explorations. Biotransformati- ons represent an effective and a preferable alternative to conventional chemical synthesis of the production of fine chemical and optically active compounds. Enzymes are important catalysts in a wide range of reactions because of their catalytic rates, specificity and function under mild conditions. As biocatalysts, enzymes exhibit enantioselectivity, preferentially reacting with only one steroisomer, and regioselectivity, preferentially reacting with only one site on a molecule despite multiple sites of potential reactions.In recent years, investigations have been started on the benefit of enzymes in various reactions related to polymer synthesis. Many new directions are emerging with respect to enzymatic condensation and ring-opening polymerizations. One important feature is the growing range of reaction conditions in which catalysis can be performed. Reactions catalyzed by enzymes in novel environments and nontraditional solvents have also led to the enhancing ability to control molecular weight and dispersity as well as the morphology and architecture of polymer products. In addition, enzyme catalysis in polymer synthesis offers several advantages relative to chemical preparative routes. Enzymes, derived form renewable resources, have promising subtrate conversion efficiency due to their high enantio- and regioselectivity, catalyst recyclability, reacting in bulk without organic solvents and representing important options to meeting environmental regulations.In the work, the general term"polyesterification"is used when polyesters are prepared from monomers, whatever the nature of the reaction. The different reaction mechanisms through which polyesterification reactions are catalyzed by enzyme are discussed as follows: ring-opening polymerizations and condensation polymerizat- ions. Enzyme-catalyzed polymerization represents a growing area of research interest in enzyme chemistry which broadly encompasses reactions such as direct condensation of diacids and diols/actived esters.The synthesis of polymers with well-defined compositions, architectures and functionalties has long been of great interest in polymer chemistry, such as atom transfer radical polymerization (ATRP). A variety of monomers have been successfully polymerized using ATRP. Typical monomers include styrenes, (meth)acrylates, (meth)acryamides, and carylonitrile, which contain substituents that can stabilize the propagating radicals. Therefore ATRP enables the preparation of novel well-defined polymeric materials.A large number of functional polymers could be synthesized effectively by combining two different polymerizations with their respective advantages. Due to their better biocompabilities and controlled structures, these new polymer products are expected to be applied in medicine, biologics, innoxious coating, rheology control agents, and so on.Based on the above reasons, we combined enzymatic polymerization and ATRP to synthesize such new functional polymers as block copolymers and hyperbranched polymers. In Chapter two, enzymatic polycondensation of benzyl-2,2-bis- (methylol) propionate and sebacic acid has been performed using Novozyme-435 as the catalyst in vacuum, subsequently enzymatic ring-opening polymerization was reacted by addingε-caprolactone as the monomer in the same system. Analyses by 1H NMR spectroscopy suggested that the resulting product was derived from the monomers with approximately equivalent–OH and–COOH at both chain ends. According to 13C NMR analyses, the copolymer showed an ordered structure comprising of two blocks. The molecular weight increased regularly from beginning of the ring-opening polymerization to its ending. The reaction monitoring results indicated that two different modes of polymerization successively took place through enzyme catalysis in one-pot to produce the AB diblock copolymer successfully. The self-assembly of the copolymer into aggregation micelles in aqueous media was determined by dynamic light scattering (DLS) and the morphology of these solventless micelles was observed by atomic force microscopy (AFM).In chapter three, the enzymatic cascade polymer product mentioned above was converted to the macroinitiator containingα-bromoester group by the estrification with 2-bromoisobutyryl bromide. The macroinitiator was employed in ATRP of Styrene (St) or glycidyl methacrylate(GMA) with the CuCl/bpy as the catalyst system to obtain the ABC triblock copolymers. The resulting triblock copolymer containing PGMA segment is considered to be amphiphilic, the self-assembly of the copolymer into aggregation micelles in aqueous media was determined by dynamic light scattering (DLS) and the morphology of these solventless micelles was observed by atomic force microscopy (AFM). As a potential surface linker for biomolecules, the triblock copolymer which contains PGMA segment has lots of promising applications in advanced biotechnology, such as DNA separation, targeted drug delivery, enzyme immobilization, and immunological assay, because of the ease in conversion of epoxide groups into a variety of functional of groups, such as -OH, -NH2, and -COOH. In addition, the epoxide-functionalized polymer brushes are promising molecular adhesive.In chapter four, a novel method for the synthesis of hyperbranched polymers was developed by combining enzymatic ring-opening polymerization (ROP) and self-condensing vinyl (co)polymerization (SCV(C)P). Functionalized polycaprolctone (PCL) was prepared by ROP ofε-CL with HEMA as initiator and catalyzed by Novozyme-435, and subsequently converted to AB* macroinimer by the esterification with 2-bromoisobutyryl bromide. The target hyperbranched polymers were obtained by SCVP of AB* macroinime and SCVCP of AB* macroinimer with St or GMA via ATRP. The hyperbranched polymers are a type of dendritic macromolecules which constitute a novel class of highly branched polymers with a multitude of end groups. Because of their highly branched three-dimentional and spherical-like molecular architecture, hyperbranched polymers have shown to exhibited the different properties from those of the linear analogues, such as low viscosity, no inter chain entangling and high solubility. And the hyperbranched polymers have a multiplicity of using range from adhesive improvers and viscosity modifiers to applications in coating, rheology control agents pharmaceuticals, and so on.In conclusion, new functional polymers which possess biocompabilities and controlled structures were produced successfully by the combination of enzymatic polymerization and ATRP.