Chemoenzymatic Synthesis Of Nonlinear Architectures Block Copolymer And Its Self-Assembly Behavior Study

The relationship between the structure and properties of copolymers have attracted more attentions and make a deep investigation,such as self-assembling behavior in solution and the morphologies of microdomain, while the synthesis of copolymers with well-defined structure is primary work in the polymer science. The development of various polymerization techniques provided the reliable experiment basis for synthesis of a series of copolymers with complicated structure, such as the cyclic, comb, star and multiblock copolymers. However, it is difficult to use a single polymerization mechanism to synthesize these copolymers, and the monomers suited for a single polymerization is also limited. Thus, it has important significance to combine the multiple polymerization mechanism to synthesize copolymers with complicated structure. By this way, the monomers available for designing are expanded and the merits of different polymerization mechanism are combined together.The combination of enzymatic ring-opening polymerization (eROP) and atom transfer radical polymerization (ATRP) have been the most potential synthesis technique.'Green'biocatalyst enzymes has been used in wide variety of polymerization reaction due to there high activity, nontoxicity, recyclability, (enatio-, regio- and chemo-) selectivity while also being environmentally friendly than conventional organometallic catalysts. Also, the process can be carried out under mild conditions. The aim of this paper is to study the chemoenzymatic synthesis of nonlinear functional multiblock copolymer by the combination of eROP and ATRP techinque。In addition, the self-assembly behavior of the relulting nonlinear block copolymers were also investigated in different conditions.In Chapter 1, we described the synthesis methods of the Y-shaped block copolymer and H-shaped block copolymer,and introduced the ATRP reaction in detail. We enumerated the virtues of biocatalyst enzyme and reviewed enzymatic polymerization in organic media. At the same time, chemical polymerizations (e.g., ATRP) appeared in chemoenzymatic synthesis reported previously were summarized in brief. Subsequently, we introduced in detail chemoenzymatic polymerization given in previous reports. More importantly, we sum up the strategies, synthesis method, functionality and potential application of chemoenzymatic synthesis related to ATRP. Finally, we sum up the self-assembly morphology of copolymer in different conditions.In Chapter 2, end-group modification method was used successfully in the synthesis of Y-shaped diblock copolymer by the combination of eROP and ATRP。The synthetic procedure involved eROP ofε-caprolactone (ε-CL) in the presence of biocatalyst Novozyme 435 and initiator 1H,1H,2H,2H-perfluoro-1-octaoxy (THPFO), subsequently the resulting PCL was converted to a macroinitiator by esterification of it with 2,2-dichloro acetyl chloride (DCAC), and lastly Y-shaped diblock copolymer THPFO-PCL-b-(PSt)2 and THPFO-PCL-b-(PGMA)2 were synthesized by the ATRP of St or GMA with CuCl/2, 2′-bipyridine as the catalyst system. The structure and composition was confirmed by NMR,IR and GPC analysis。The thermal and crystallization properties was investigated with DSC and XRD。The self-assembly behavior of Y-shaped diblock copolymer THPFO-PCL-b-(PGMA)2 was investigated in different solvents and at different concentrations. The aggregates of various morphologies (spheres, wormlike patterns, dendritic patterns and cylinders) were observed.In Chapter 3, we synthesized novel Y-shaped triblock copolymer by the chemoenzymatic route. First, CCl3-terminated PCL were prepared by eROP ofε-CL in the presence of initiator 2.2.2-trichloroethanol (TCE) and biocatalyst Novozyme 435, followed by the quantitative esterification of the resulting macromonomer with DCAC to obtain trifunctional macroinitiator. The well-defined Y-shaped block copolymer PSt-b-PCL-b-(PSt)2 and PGMA-b-PCL-b-(PGMA)2 was then synthesized by ATRP of styrene or GMA. The macromolecular structures and physical properties have been characterized by HNMR and FTIR, DSC. GPC was used to measure the molecular weight and molecular weight distribution. In addition, the self-assembly behavior was investigated in different solvents and at different concentrations. The aggregates of various morphologies (spheres, wormlike patterns, network patterns and cylinders) were observed.In Chapter 4, we carried out the chemoenzymatic synthesis of amphiphilic ABC2-Y-shaped triblock copolymer PEO-b-PCL-b-(PSt)2 , PEO-b-PCL-b-(PGMA)2, the strategy was the same as that used in the preparation of dibolck copolymer in Chapter 2, except that the initiator THPFO was replaced with monohydroxyl PEG (CH3O-PEO-OH) during eROP; For the PSt-b-PCL-b-(PGMA)2, a CCl3-trichloromethyl-terminated PCL macroinitiator was synthesized by the eROP ofε-CL from a bifunctional initiator TCE. Subsequently, the resulting PCL macroinitiator was used to initiate the ATRP of styrene to obtain AB diblock copolymer, which converted to a dichlorine-ended macroinitiator by esterification of it with DCAC,which was used for the following ATRP of GMA. The self-assembly behavior of resulting polymer was investigated in different conditions. The aggregates of various morphologies (spheres, wormlike patterns, network patterns and ring-shape pattern) were observed. In the process, solvent greatly influenced the morphologies of the films. For example, for PSt-b-PCL-b-(PGMA)2, as the solvent was changed from DMF to dioxane, the morphology of copolymer 4 changed from spheres into wormlike patterns. In THF, the network patterns were formed. Also, the surface morphologies showed strong dependence on the solution concentration: with increasing concentration, the ring-shape patterns were changed into cylinders in acetonitrile.In Chapter 5, we carried out the chemoenzymatic synthesis of amphiphilic C2BABC2-type pentablock copolymer (PSt)2-b-PCL-b-PEO-b-PCL-b-(PSt)2 and (PGMA)2-b-PCL-b-PEO-b-PCL-b-(PGMA)2 with dihydroxyl PEG (HO-PEO-OH) as initiator during eROP. The structures and properties have been characterized by HNMR, FTIR, and GPC. In addition, the self-assembly behavior was investigated in different solvents and at different concentrations. Surprisingly, the aggregates of various morphologies (spheres, wormlike patterns, network patterns and cylinders) were observed. In this work, the successful synthesis of block copolymers indicated the good compatibility between eROP and ATRP.