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

Block copolymers has been received great interest because of its unique properties such as impact-resistant plastics, different phase behavior, thermoplastic elastomers, variety of morphologies, polymeric emulsifiers, sol-gel states, and gas permeation membranes.In the first section of Chapter 1, 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.In chapter 2, symmetric linear pentablock copolymers consisting of ploy(ethylene glycol)(PEG), polycaprolactone (PCL) and 2,2,3,4,4,4-Hexafluorobutyl methacrylate (PHFMA) and GMA was synthesized by means of the enzymatic ring-opened polymerization(eROP) combined with atom transfer radical polymerization(ATRP). Dihydroxyl PEG initiated eROP ofε-CL to synthesize the hydroxyl group terminated polyester PCL-b-PEG-b-PCL. Theα-bromoester terminated macroinitiator Br-PCL-b-PEG-b-PCL-Br was obtained in the subsequent modification of end hydroxyl groups that was suitable for block ATRP of fluorinated monomer (PHFMA) and GMA. Pentablock copolymers PHFMA-b-PCL-b-PEG-b-PCL-b-PHFMA and PGMA-b-PCL-b-PEG-b-PCL-b-PGMA was obtained via the further ATRP. 1H NMR and IR measurements were used to confirm the macroinitiator and architecture of the pentablock copolymer .GPC testifies that this method is feasible and its kinetics analysis indicates a living/controlled radical polymerization. The micelle diameter was investigated by virtue of dynamic light scattering(DLS).The self-assembly behavior of the pentablock copolymer was investigated in aqueous media.In chapter 3, Novel Y-shaped block copolymers were synthesized by using dichloropolyester, initially synthesized by ROP of PCL, as macroinitiators for the ATRP of GMA. The structures of all the polymer products were well characterized by means of NMR, GPC, and IR measurement. The combination of these two processes affords well-defined copolymers of a wide array of compositions. The PCL: PGMA ratios of each constituting block significantly influenced the properties of the copolymers, especially micellization properties. These copolymers represented a unique set of PCL/PGMA analogous Y-shaped copolymers, of which the self-assembling behavior in aqueous media had been studied in detail. Self-assembling of Y-shaped block copolymers led to the formation of different morphologies. The morphology of these Y-shaped block copolymers examined by AFM showed various morphologies such as normal spherical micelles, vesicles, lamellae, and large compound micelles (LCMs). Moreover, it was found that both the copolymer composition and the copolymer concentration in THF had a great influence on the morphologies of the aggregates. In addition, experiments aimed at the effect of the solvent nature, temperature, and storage time of the morphologies are under way.The ATRP macroiniitiator effectively initiated ATRP of styrene with CuCl/2,2`-bipyridine as the catalyst system. Linear first-order kinetics, linearly increasing molecular weight with conversion, and low polydispersities (less than 1.29) were observed in this process. The structures and composition of the Y-shaped copolymer were well characterized by means of NMR, IR and GPC measurement. DSC analysis showed that the crystallinity of the copolymer decreased with the introduction of the PSt block. Chemoenzymatic synthesis of Y-shaped block copolymer is a novel technique, which not only allows the variation of the polymer composition by adjusting the ratios between the macroinitiator and monomer, but also can control the structure of polymer exactly. In addition, the research for the morphology of Y-shaped block copolymers is in progress. In Chapter 4, our group proposed a simple strategy for a novel idea, i.e.enzymatic polycondensation was combined with ATRP to inspect further the compatibility between biocatalytic technique and chemocatalytic technique. A novelω-hydroxyester 2,2,2-trichloroethyl 10-hydroxydecanate P(TCE-10-HD) was firstly synthesized and used in eSCP to obtain linear polyester P(TCE-10-HD), whose terminal was occupied by the ATRP initiating groups, -CCl3. The macroinitiator started the ATRP of St and GMA to prepare diblock copolymer P(TCE-10-HD)-b-PGMA. The introduce of eSCP expanded the category of enzymatic polymerization in chemoenzymatic polymerization, which inaugurated a new research domain. Well-defined diblock copolymer poly (2, 2, 2-trichloroethanol 10-hydroxydecanate)-block-poly (glycidyl methacrylate) [P (TCE-10-HD)-b-PGMA] was obtained by combining the enzymatic condensation polymerization and ATRP. P (TCE-10-HD) was firstly prepared by enzymatic condensation polymerization of 10-HD and, within the same step, TCE. This -CCl3 terminated polyester permitted the subsequent ATRP of GMA without other steps. The structures of the polymers were characterized by NMR, FTIR. The kinetic results were measured by GPC. The self-assembly behavior of the amphiphilic diblock copolymer was also investigated. The morphology of the assembly particles were studied by AFM, TEM and SEM.