Precise Control On Chain Sequence Structures Of Styrene/Butyl Acrylate Copolmers Via A Model-aided Semibatch RAFT Polymerization

Nowadays,the development focus of chemical industry has shifted from the improvement of the efficiency of large-scale production of general products to the development of efficient and green manufacturing technologies for high-performance specialty products.The performance of polymer material is determined by the polymer chain structure,which is fundamentally controlled by its monomer sequence along the chains.Therefore,precisely controlling the connection order of the monomer units in the polymer chain is the key to customizing the material performance.Driven by this industrial demand,this work combines semibatch polymerization method with reversible addition-fragmentation chain transfer(RAFT)model to achieve rapid and precise customization of copolymer composition,while also allowing for precise control of the copolymer sequence structure via model-based monomer feeding strategy.The main research contents of this doctoral thesis include:the development of RAFT solution copolymerization model,which was used to study the effect of chain transfer reactions on molecular weight distribution.This model was validated using styrene(St)/butyl acrylate(BA)RAFT solution copolymerization kinetic data.The resulting model was subsequently combined with a semibatch reactor model,thus making it possible to obtain uniform copolymer composition distribution(CCD)via Policy ? RAFT solution copolymerization of St and BA.Furthermore,in order to achieve green and rapid preparation of polymers,RAFT mini-emulsion copolymerization was conducted to synthesize St/BA copolymers with different uniform copolymer sequence by utilizing programmed monomer feeding processes.The Monte Carlo method was used to visualize the monomer sequence of copolymer chains,and copolymer triads and sequence length distribution(SLD)of St/BA copolymers prepared by RAFT miniemulsion polymerization were calculated.The conclusions achieved in the aforementioned research works include:(1)RAFT solution copolymerization model with chain transfer reactions to monomer and solvent was developed.It was found that as the chain transfer constant to monomer and solvent increased and the monomer concentration decreased,the deviation of the polymer molecular weight from the theoretical value increased and the distribution became broader.In addition,the model developed can predict St/BA RAFT solution copolymerization kinetics well.(2)RAFT solution copolymerization model was coupled with semibatch reactor model.The resulting model was used to apply Policy ? monomer feeding strategy to produce St/BA copolymers having uniform CCD.The use of Policy ? feeding strategy increased the polymerization rate by more than 2 times compared with that of Policy ?feeding strategy was used.(3)Semibatch RAFT miniemulsion sequence model was derived.This model made it possible to prepare St/BA copolymers with uniform number-average sequence length equal to 2(SLn=2)by programmed monomer feeding,and copolymer triads were constant.(4)Using the Monte Carlo method,a visualization technology that can display the structure of the monomer sequence in the copolymer chain was developed.It was found that copolymer sequence drifts during batch polymerization,while SLD of St/BA copolymers with uniform SLn=2 did not change with the increase of conversion.Besides,with the increase of copolymer composition,SLD became broader.