Study On The Synthesis Of Poly （Carbonate-Ether） Polyols Via Copolymerization CO₂/1,2-Butylene Oxide Over Double Metal Cyanide Catalyst

Poly（carbonate-ether）polyols is a kind of polymer material containing ester bond and ether bond.It is mainly used as precursor for synthesis of polyurethane,which is widely applied in the fields of automobile,medical instrument,electronic material and so on.The synthesis of poly（carbonate-ether）polyols by the copolymerization of CO₂ and epoxy-alkanes is the main way to realize the chemical utilization of CO₂ and the preparation of degradable polymer materials.In this thesis,a double metal cyanide（DMC）catalyst was employed to solve the problems in the synthesis of（1,2-butylene oxide）-based poly（carbonate-ether）polyols via CO₂ and 1,2-butylene oxide（BO）copolymerization,such as the difficulty of ring-opening for BO and activation for CO₂,low catalytic efficiency and poor thermal stability of the copolymer.The activity-structure relationship of the catalyst and the reaction mechanism were studied.In addition,the third monomerε-caprolactone（CL）was introduced to study the ternary copolymerization of CO₂/BO/CL,which improved the thermal properties of the copolymer.The study provides a theoretical reference for the green synthesis of（1,2-butylene oxide）-based poly（carbonate-ether）polyols.The main research progress and conclusions are as follows:（1）DMC bearing alpha hydroxyl acid（AHA）complexing agents was used for synthesis of（1,2-butylene oxide）-based poly（carbonate-ether）polyols by CO₂ and BO copolymerization.The introduction of AHA not only changed the crystallinity of the catalyst,but also changed the electronic environment of Zn atom in the catalyst and the coordination mode with the complexing agents,as well as increased the molar fraction of CO₂ in copolymer(f _CO2).Under the reaction condition of 90°C and 3 MPa initial CO₂ pressure,DMC-MA-P123 containing double carbonyl group achieved BO conversion of 91.0%,f _CO2 of 30.9%and catalytic productivity of 275 g polymer/g catalyst.It was confirmed by COSY NMR that DMC-catalyzed CO₂/BO copolymerization belonged to cationic ring-opening polymerization.（2）Layered Zn-Co double metal cyanide（L-DMC）catalyst with acetic acid as complexing agent was also used in the copolymerization of CO₂ and BO.Activity-structure relationship analysis showed that L-DMC had more active sites due to its smaller particle size and larger specific surface area.In addition,acetic acid complexing agent affected the catalytic activity and f _CO2 by affecting the active center of Zn.Under the optimum conditions,f _CO2 could reach 35.5%and catalytic productivity could reach 1500g polymer/g catalyst.In-situ FTIR results showed that there was a competitive relationship between target product and BC by-products,and it was speculated that the existence of carboxylic acid in acetic acid complexing agent of L-DMC was the key factor to realize efficient fixation of CO₂.（3）The CO₂/BO/CL ternary copolymerization was studied by introducing the third monomer CL into the CO₂/BO copolymerization system.Characterization results showed that the increase of CL could increase the content of polycaprolactone units（PCL）,decrease the content of carbonate units（PBC）and decrease the content of polyether units（PBO）.The maximum weight loss temperature(T_d,nmax)of the terpolymer was mainly affected by the content of polycaprolactone units and polyether units.It was suggested that the introduction of CL improved the thermal stability of the copolymer.