The Chemical Control In Polyester Materials Synthesis

Polyester materials have attracted much attention because of the widely available and green/sustainable properties of their raw materials,along with their good degradable properties.With the consumption of petroleum resources and the huge pollution to the environment,the research and usage of polyester materials have attracted extensive attention from both academia and industry.Although there are many synthetic methods for the synthesis of polyester materials,it has becoming more and more challenging to access new polyester materials through the development of new catalysts and new monomers.Therefore,it is particularly important to develop novel regulatory strategies for the synthesis of polyester materials.In this thesis,we introduced new strategies to prepared polyester materials with novel structures and excellent properties in their synthetic processes.Among them,the strategies we studied mainly include tandem catalysis,cocatalyst control and photoresponsive control.The successful application of these regulatory strategies in the synthesis of polyester materials may also be extended to other catalysis fields.The specific innovation achievements are summarized as follow:1.Firstly,a tandem catalysis concept was introduced to the system of copolymerization of epoxy compounds and cyclic acid anhydrides for the synthesis of polyester materials.A simple and readily-available Mn-salen complex could catalyze copolymerization of epoxides with unsaturated cyclic anhydrides to prepare a series of unsaturated polyesters;The Mn-Salen catalyst can continue to catalyze the epoxidation or ring-opening aminolysis reaction to generate epoxy-or arylamine-functionalized polyesters by one-pot method;curing of the epoxy-functionalized polyesters with cyclic anhydrides to prepare cross-linked epoxy resins;transesterification induced dynamic exchange of cross-links in the epoxy resins to afford a vitrimers system.This tandem catalysis system required minimum workup and intermediate isolation,making it a highly efficient method to prepare various polyester materials with great properties using one catalyst in one pot.2.Secondly,a cocatalyst strategy was introduced to the system of preparing polyester materials by the ring-opening metathesis polymerization(ROMP)/cross-metathesis(CM)of cycloolefins in the presence of substrates such as chain-transfer agents(CTAs).A commercially available cocatalyst(NaBArF)interacts with a variety of ruthenium catalysts to form ruthenium metal cation centers.Compared with the system without the addition of cocatalyst,the higher catalytic efficiency in the copolymerization of cyclooctene and chain transfer reagent with electron withdrawing group,resulting in the preparation of telechelic polymers with controllable molecular weight and degradable random copolymers.Furthermore,the polymer microstructure can be regulated in situ through cocatalyst enabled reactivity differences of catalyst towards substrates.3.Subsequently,the above-mentioned polymerization methods and regulatory strategies was combined organically.We prepared unsaturated terpolymers using epoxy compounds and acid anhydrides.The unsaturated terpolymers can serve as reactive macromonomers for the introduction of polyolefin segments by taking advantage of this metathesis cocatalyst strategy,leading to the formation of multi-block polyethylene-polyester copolymers.These saturated multi-block polymers demonstrated great compatibilization effects for mixtures of different polymers,which may be applied to solve the difficult issues of mixed plastic recycling.4.Finally,photoresponsive strategy was applied the ring-opening polymerization of lactide.A series of(thio)ureas bearing dithienylcyclopentene optical molecular switch moiety were designed,synthesized,and characterized.It was found that the photoresponsive(thio)ureas catalyst exhibited higher catalytic efficiency in the ring-opening polymerization of lactide than the original catalyst,and the resulting polylactic acid had a narrower molecular weight distribution.More importantly,the regulation of the lactide polymerization process can be achieved by using the selective responsiveness of the catalyst towards UV/visible light.