Preparation Of Polybutadiene-based Block Copolymer By Coordinative Chain Transfer Polymerization

Cis polybutadiene rubber is an important rubber in the field of synthetic rubber because of its excellent mechanical properties,fatigue resistance and low temperature resistance.However,because polybutadiene is a non-polar polymer,its compatibility with inorganic fillers or other polar polymers is poor.Aliphatic polycarbonate is a kind of important biodegradable polymer material,which is widely used in surgical and medical materials,pharmaceuticals,agriculture and primary packaging.The purpose of this thesis is to introduce polar polycarbonate segments into polybutadiene,so as to improve its blending compatibility with polar materials and increase its added value.The main work is to prepare block copolymers of polybutadiene and polycarbonate through coordination chain transfer polymerization and ring opening polymerization with rare earth catalyst system.The specific research contents are summarized as follows:Butadiene polymerization was catalyzed by Nd?vers?₃/Al?iBu?₂H/Me₂SiCl₂ system.The effects of the amount of monomer butadiene and alkyl aluminum on the polymerization were investigated.The results show that the system has the characteristics of coordination chain transfer polymerization in the range of[Al]/[Nd]=20⁵0.The molecular weight of the obtained polymer is controllable and its distribution is narrow.On average,5⁸ polymer chains can be produced in each active center.Based on the system,the polymerization of butadiene has the characteristics of controllable polymerization,and the PBD-b-PCHO copolymers with different compositions are prepared by the stepwise feeding method.FTIR,¹H NMR,DSC and other test results show that the molecular weight composition is close to the feed ratio,and the molecular weight of the polymer is monodisperse.After optimizing the catalytic system and feeding method,the second-stage polymer was introduced with the cocatalyst PPNCl in the original catalytic system,and simultaneously introduced with CHO and CO₂,and finally a series of monodispersed PBD-b-PCHC copolymers were obtained.Further,the various factors affecting the catalytic efficiency were investigated in detail.The experimental results show that the catalytic efficiency can reach up to 2217 g/?mol-Nd h?under the conditions of 40 ^oC,CO₂pressure of 12 atm,and polymerization for 24 h..The appearance of-C=O and C-O in the FTIR curve and the NMR curve both attribute the characteristic peaks.After the introduction of the PCHC segment,two Tg appeared in the DSC curve,and the Tg of the polybutadiene segment increased from-106.4 ^oC to-91.56 ^oC.In addition,TGA test results show that PBD-b-PCHC has high thermal stability below 240 ^oC.A series of block copolymers?PBD-b-PTMC?of monodisperse polybutadiene and polycarbonate cyclohexene ester were prepared by using Nd?vers?₃/Al?iBu?₂H/Me₂SiCl₂ as catalyst system,and the composition of the copolymers can be controlled by the feeding ratio.The copolymerization of BD and TMC catalyzed by rare earth catalyst system was studied systematically.The results showed that the highest catalytic efficiency was 14216h^-1 at 35 ^oC.The results of FTIR and NMR showed that PBD-b-PTMC block copolymers were successfully prepared.Two glass transition temperatures appeared in DSC curves,which further verified the structure of block copolymers.