Study On RAFT Polymerization Of Acrylates By Gradient Polymer Elution Chromatography

With the increasing requirements for precise control of the polymer structure and polymerization process,people have paid more and more attention to various low-probability reactions in the polymerization process of acrylate.Reactions such as head to head addition and chain transfer in acrylate polymerization significantly affected the structure and properties of the polymer in reversible deactivation radical polymerization especially.In this paper,benzyl N-carbazole dithiocarboxylate(BCBD)was used as the RAFT agent,and the combination of RAFT polymer block derivatization and Gradient polymer elution chromatography(GPEC)was used to determine the head addition incidence(?1)of methyl acrylate(MA)and its dependence on temperature.The above method was also used to determine the transfer rate constant of PMAduring polymerization of ethyl acrylate(EA).BCBD was used as the RAFT agent and 2-methoxyethyl acrylate(MOEA)as the block-derived monomer.The GPEC separation condition of the RAFT polymerization product RPMA and the block RPMA-b-PMOEA was improved.The content of dead dormat species(DDS)due to head addition during MAFT polymerization of MA was calculated,and the ?1 of MA at different temperatures were estimated.The results showed that the ?1 of MA at 60,70,80 and 90? was 2.04 × 10-3,2.37 × 10-3,2.72 ×10-3 and 3.28 × 10-3 respectively,and the activation energy was 15.8 kJ/mol.The ?1 of MA is the highest of the alkyl acrylate,which is consistent with the smallest steric hindrance of its ester group.Isopropanol was used as the chain transfer agent to prepare a low molecular weight PMA with tertiary hydroxyl groups(named as iPr-PMA),and BCBD was used as the RAFT agent to conduct RAFT polymerization of EA in the presence of iPr-PMA.The GPEC separation conditions were determined,and the use of dichloroethane/methanol can eliminate the strong adsorption of terminal hydroxyl groups of iPr-PMA on silica gel.We successfully completed the separation and content determination of RAFT polymerization product RPEA and the block iPr-PMA-b-RPEA generated by chain transfer.The intermolecular chain transfer constant of PEA growth radicals to iPr-PMA at different temperatures were estimated,about 3.5 × 10-5 during bulk polymerization at 100?.The establishment of this method provided a feasible method for in-depth study of dynamics and influencing factors of intermolecular chain transfer.