Synthesis And Property Adjustment Of Carbon Dioxide-Cyclohexene Oxide Copolymer

Fixing CO2 into polymers through the copolymerization of carbon dioxide and epoxide is appealing.Such approaches not only make use of the greenhouse gas,meeting the need of carbon neutrality,but also turn CO2 into Cl resources,reducing the consumption of fossil resource.CO2-based copolymers,especially propylene oxide/CO2 copolymers(PPC)have attracted considerable attention due to their excellent properties such as biodegradability and high barrier properties.However,owing to the low glass transition temperature(Tg<40 ℃),PPC cannot be utilized in high temperature.In contrast,poly(cyclohexene carbonate)(PCHC)derived from the copolymerization of CO2/CHO shows a high Tg of above 110℃ with good mechanical strength but suffers from high brittleness.This thesis focuses on the modification of PCHC in order to enhance PCHC properties.We had synthesized PCHC with different topological structure in various methods,and investigated the performance of PCHC.The detailed results are summarized as follows:1.We obtain linear soft PCHC-based polymers by terpolymerization.A green porphyrin aluminum catalyst was used in the terpolymerization of CHO/CO2/terminal epoxide to get a gradient terpolymer with random distribution of CHC segments in the polymer backbone.The molecular weight and segment structure composition of the terpolymer could be controlled by adjusting the initial feed ratio and reaction time.Moreover,by adjusting the terminal epoxide side group length/CHC bond content,we successfully synthesized polycarbonates with glass transition temperatures from-14℃ to 113℃without loss of thermal stability.Through tensile testing,we confirmed the effectiveness of the toughness improvement through modification.When 70%butylene oxide was inserted,the elongation at break could be increased to 200%.2.We report a facile and feasible strategy to transform brittle plastic PCHC into functional elastomer through the ingenious introduction of Cu-S dynamic metal reversible bonds.As a proof-of-concept,4-vinyl cyclohexene oxide(VCHO)with vinyl side group was introduced into the backbone of PCHC via the terpolymerization of CHO/VCHO/CO2 catalyzed by a high activity double metal cyanide catalyst.Given the high efficiency of thiol-ene click chemistry,thiols with long alkyl chain were attached to the vinyl blocks to tailor the flexibility and functionality of PCHC.Notably,the sulfur atom can naturally form Cu-S dynamic reversible metal coordination bonds to afford a cross-linking PCHC network with thermoplastic elasticity when simply mixing with Cul.The resulting polymers displayed tunable thermal and mechanical properties,depending on the amount of metal,with Tg ranging from-3 to 41℃,mechanical strength ranging from 1.7 to 23 MPa,and elongation at break ranging from 9%to 1210%.Especially,the polymer with 20%CuI addition had excellent elastic recovery at 75℃ and remained 86%of its initial mechanical performance after five cycles of tensile testing.Moreover,the polymer possessed the ability of self-healing,reprocessing and other functions.3.Applying the method of macromolecular chain transfer agent to generate ABA block copolymer with polyethylene glycol(PEG)as the soft segment.Combining the characteristics of immortal polymerization,we introduced PEG with different molecular weight into the CHO/CO2 copolymerization.We studied the effects of catalysts and macromolecular chain transfer agents on polymerization activity and products.By adjusting the initial feed ratio,we gained the block copolymer PCHC-b-PEG-b-PCHC with PCHC as the hard segment.In conclusion,this paper enriches the modification methods and develops the topological structure based on PCHC,which has a certain enlightening effect on the on PCHC structure and feature research.