Synthesis And Characterization Of Block Copolymer By Enzymatic Condensation Polymerization And ATRP

Enzyme have traditionally been used in biochemical studies, molecularbiology and related scientific explorations. Biotransformations represent aneffective and sometimes a preferable alternative to conventional chemicalsynthesis for the production of fine chemical and optically active compounds.Enzymes are important catalysts in a wide range of reactions because of theircatalytic rates, specificity and function under mild conditions. As biocatalysts,enzymes exhibit enantioselectivity, preferentially reacting with only onesteroisomer, and regioselectivity, preferentially reacting with only one siteon a molecule despite multiple sites of potential reactions. In recent years,investigations have been begun on the benefit of enzymes in various reactionsrelated to polymer synthesis. Many new directions are emerging with respectto condensation, ring-opening and controlled free radical polymerizations.One important feature is the growing range of reaction conditions in whichcatalysis can be performed. Reactions with enzymes in novel environmentsand nontraditional solvents have also led to the enhanced ability to controlmolecular weight and dispersity as well as the morphology and architecture ofpolymer products. In addition enzyme catalysis in polymer synthesis offersseveral advantages relative to chemical preparative routes. Enzyme, derivedform renewable resources, have (a) promising subtrate conversion efficiencydue to their high selectivity for a given organic transformation, (b) highenantio-and regioselectivity, (c) catalyst recyclability, (d) can be used in bulkreaction media avoiding organic solvents and (e) represent an important optionin meeting environmental regulations.In the following the general term "polyesterification" is used when apolyester is prepared from monomers, whatever the nature of the reaction. Thedifferent reaction mechanisms through which enzyme catalyzedpolyesterification reactions occur are discussed as follows: (a) ring openingpolymerizations (b) condensation polymerizations and (c) transesterficationreaction of polyester substrates. Enzyme catalyzed condensationpolymerization represents a growing area of research interest in enzymechemistry which broadly encompasses reactions such as direct condensationof diacids and aiols/ hydroxyl acids and condensation polymerization ofactived esters. But, enzyme catalyzed diacids and aiols/ hydroxylcondensation polymerization from racemic low molar esters.The synthesis of polymers with well-defined compositions, architectures,functionalties has long been of great interest in polymer chemistry, such asatom transfer radical polymerization (ATRP). A variety of monomers havebeen successfully polymerized using ATRP. Typical monomers includestyrenes, (meth)acrylates, (meth)acryamides, and carylonitrile, which containsubstituents that can stabilize the propagating radicals. therefore it enables thepreparation of novel well-defined polymeric materials.In chapter 2, Novozyme-435 is used to catalyze the polycondensation ofdiacids/diols, ω-hydroacid and ω-hydroester. It is indicated that the resultingpolyesters are terminated with different groups by means of 1H-NMR,FTIR-IR, GPC analysis, at the same time, that Novozyme-435 is high activecatalyst and have selectivity. In addition, during enzymatic polycondensation,Novozyme-435 enables the degradation of the resulting polyester. And theoptimal reaction condition and polymerization time are chosen via the kineticsstudy of enzymatic polycondensation in order to obtain the highest molecularweight. The resulting polyester have extensive application in modern polymerscience. Moreover, this polymerization method is not reported in previousliterature.In chapter 3 and 4, we firstly reported that block copolymers aresynthesized by the combination of enzymatic polycondensation and ATRP.Polyester macroinitiator is prepared by the modification of end groups andpermits the subsequent block-ATRP of St and GMA. The XRD, DSC, AFM,DLS measurement indicates that the introduce of PSt and PGMA makes thecopolymer crystallinity lower. At the same time, the melting temperatureincreases and the crystallinity temperature decreases. The resulting blockcopolymers can self assembly into nanospheres though supermolecular action.Much attention has been likewise focused on the development of blockcopolymer using as surfactants, adhesives, thermoplastic elastomers anddispersants, because of the fact that their special structures can bring on theunique polymer properties to yield novel materials. Different techniques forthe preparation of copolymer have been developed, in which the difunctionalinitiator carrying two dissimilar monomers has been used. As a potentialsurface linker for biomolecules, poly-(glycidyl methacrylate)(PGMA) haspromising application 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 offunctional of groups, such as -OH, -NH2, and –COOH,In addition, theepoxide-functionalized polymer brushes are promising molecular adhesive.