Computer Simulation In Polymer Synthesis And Predication Of Polymer Proprerties

With the fast development of the computer technique, computer simulation has been playing more and more important roles in polymer science. Computer simulation, as another kind of effective research approach besides theory and experiment approach, can not only predict the properties of materials, but also provide insights into how material behavior is related to molecular properties. In this thesis, the applications of computer in polymer science were investigated in five facets. The various functional softwares were developed by using a visible program designing language Visual Basic tool.Firstly,the reactivity ratios of radical copolymerization are determined by intercept-slope method, YBR method, JJ method (linear intersect), TM method (non-linear least squares) and microcomputer dynamic search method using microcomputer. Among these methods ,the TM (non-linear least squares) method and microcomputer dynamic search method can gained the more precision results. Based on the copolymerization integral equation, the relative curves of the monomer composition, copolymer instantaneous composition and copolymer average composition with the monomer conversion are drawn up. In addition, the distribution of the copolymer segment and monomeric unit were simulated and gave their distribution curves.Secondly,Based on the Monte Cairo method ,the simulation of the formation of defective structures in PVC by computer software at different conversion was carried out. The simulation results showed that when the conversion is more than 0.85-0.87, the defective structures generally increase as the monomer conversion increase.Thirdly,the thermal decomposition Kinetics of polymer was studied by means of thermalgravimetry. The cubic spine function can be used in interpolating and differentiating the thermalgravimetry data, and then the resulting data are treated by binary regression, thus we can get the thermal decomposition activation energy E, the reaction order n as well as the frequency factor A. Therefore it is a very simple and convenient method. The thermal decomposition Kinetics parameters can indicate the heat resistance quantitatively and confirm the relation of heat decomposition rate with temperature, it is very useful for application.Forthly,the group contribution method provides a better assistant means for designing and developing the new polymer materials. The Visual Basic software has friendly interface and convenient operation. The group contribution method is a better method for predicting the propertis of the weak polar polymers but not so well for the strong polar polymers. In addition, there are only 33 kinds of basic group in the group contribution method, so it is hardly to predict the properties of complex structure polymers .Finally,Several important physical properties of polymers,such as mole volume, solubility parameter, surface tension, refractive index, dielectric constant and glass transition temperature have been determined by connectivity index method using microcomputer. The correlationcoefficients and standard deviations were determined for evaluating the precision. In this paper ,a kind of novel fluorine-containing polyimides were prepared ,for predicting this kind of polyimids using connectivity index method, a multiple linear regression equation are present by author . In short, the connectivity index method has the more wide application and can get more precise results than group contribution method but its operation is rather complex.