Synthesis Of Novel Functional Block Copolymer And Self-Assembly Study

In chapter 1, we sum up the development of the Combining Enzymatic Polymerization and ATRP and Its Self-Assembly Behavior.Enzyme have traditionally been used in biochemical studies, molecular biology and related scientific explorations. Biotransformations represent an effective and sometimes a preferable alternative to conventional chemical synthesis for 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 begun on the benefit of enzymes in various reactions related to polymer synthesis. Many new directions are emerging with respect to condensation, ring-opening and controlled free radical polymerizations. One important feature is the growing range of reaction conditions in which catalysis can be performed. Reactions with enzymes in novel environments and nontraditional solvents have also led to the enhanced 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. Enzyme, derived form renewable resources, have (a) promising subtrate conversion efficiency due to their high selectivity for a given organic transformation, (b) high enantio- and regioselectivity, (c) catalyst recyclability, (d) can be used in bulk reaction media avoiding organic solvents and (e) represent an important option in meeting environmental regulations.In the following the general term"polyesterification"is used when a polyester is prepared from monomers, whatever the nature of the reaction. The different reaction mechanisms through which enzyme catalyzed polyesterification reactions occur are discussed as follows :(a) ring opening polymerizations (b) condensation polymerizations and (c) transesterfication reaction of polyester substrates. Enzyme catalyzed condensation polymerization represents a growing area of research interest in enzyme chemistry which broadly encompasses reactions such as direct condensation of diacids and aiols/ hydroxyl acids and condensation polymerization of actived esters. But, enzyme catalyzed diacids and aiols/ hydroxyl condensation 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 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 it enables the preparation of novel well-defined polymeric materials.In chapter 2,the chemoenzymatic synthesis of block copolymers from bilfiunctional initiator using enzymatic ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) in two consecutive steps was investigated. First, the novel bifunctional initiator 2,2,2,-trichloroethanol (TCE) was used via an biocatalyst novozyme-435 ring-opening polymerization (ROP) ofε-caprolactone (ε-CL),then which initiated ATRP of methylmethacrylate (MMA). AB-type diblock copolymers of polycaprolactone (PCL)-block- polymethylmethacrylate (PMMA) was obtainted .The structure was determined by NMR spectrum and GPC. polydispersity index of diblock copolymers Kinetic analysis of ATRP of MMA indicated a living/controlled radical polymerization .In chapter 3, the chemoenzymatic synthesis of pentablock copolymer of [poly(4-vinylpyridine)-block-poly(?-caprolactone)-block-poly(ethyleneglycol)-block-poly(?-caprolactone)-block-poly(4-vinylpyridine)](PVP-b-PCL-PEG-PCL-b-PVP) was prepared by combining of enzymatic ring-opening polymerization( ROP ) of ?-caprolactone (?-CL) and atom transfer radical polymerization( ATRP) of 4- vinylpyridine(4-VP) in sequential. Firsty, polyethyleneglycol (PEG) initiated enzymatic ROP of ?-CL in the presence of the biocatalyst Novozyme-435. And then the hydroxyl group of terminal of PCL-b-PEG-b-PCL are modified by 2-Bromopropionyl bromide as macroinitiator of ATRP and Br-PCL-b-PEG-b-PCL-Br effectively initiated ATRP of VP with CuCl/ HMTETA as the catalyst system. GPC analysis of block copolymerization indicated that this is a living/controlled process, the polydispersity is 1.18. 1H NMR spectroscopy was used to determine the chemical composition of the block copolymers. XRD resulte showed threeblock copolymer is crystal ,diffraction appear at 2θ=21°和2θ=24°. Wten the moleculer weight of pentablock copolymer is 23000,the diffraction became low. Wten the moleculer weight of pentablock copolymer is 26000, the dispersion appear. The resulting pentablock copolymer can self-assemble into"crew-cut"aggregates. the sphere morphologies were observed.PNIPAM - PCL―PEO―PCL―PNIPAM pentablock copolymer were synthesis vary morphologies were observed such as normal spheres, nonarods, , nanowire etc. To our knowledge, this is the first example of crew-cut aggregates of amphiphilic symmetric pentablock copolymers. The study showed the morphologies of"crew-cut"aggregates were affected by the block copolymer composition as well as the copolymer concentration in the initial solution THF and DMF. The higher content in pentablock copolymer and the lower copolymer concentration in THF enabled the change of the aggregates for the more stable morphologies, from sphere to rod, In conclusion, the copolymer composition ,solvent and solvent concentration played a major role in determining the morphologies of the aggregates; however, the copolymer concentration was also relevant.In chapter 4, the homopolymer brushes of poly(4-vinylpyridine) (PVP) was prepared by the"graft from"method using atom transfer radical polymerization (ATRP) on the modified silicon wafer by the initiator which was prepared by vapor method (the silicon gel was treated with the vapor of 3-aminopropylthiethoxysilane, followed by amidization with the 2-bromopropionyl bromide). And PVP metal complex was formed by subsequent treatment with either aqueous AgNO3 or CuCl2. Attachment of Ag+ or Cu2+ to he PVP brush was confirmed using IR, water contact angle, XPS and AFM. These surface functionalized brushed have stimulated significant theoretical but limited experimental interest. Such surfaces potential use is in the synthesis of inorganic metalnanoparticles by reduction. These samples were characterized by FT-IR, XPS, water contact angle and AFM. The results of the brushes before and after reduction demonstrates that upon treatment with NaBH4 the brush surface changes from smooth and featureless to having definite surface features, which we attribute to the formation of metal nanoparticles with in the polymer brush. These surface contained metal nanoparticles may have important applications in fields such as"smart"coatings, biosensors, and colloid stabilization.