Computer Simulation Of Polymer Chains In Dilute Solution And Its Applications In Modeling The Elution Behavior Of Polymers In Size Exclusion Chromatography

With the development of high performance computing facilities and computational algorithms, computer simulation has gradually developed into an unique polymer science research method, which is playing a more and more important role in revealing the relationships between structure and properties of polymer and an optimized design of polymer materials. Size exclusion chromatography(SEC) in polymer characterization plays an indispensable role. It is worth noting that, theory and experiment complement and test each other so that we have the opportunity to better understand the ambiguous problems in the experiment. In this paper, by combining the polymer theory and some of the existing research results of size exclusion chromatographic, a further study about computer simulation of polymer chains in dilute solution and its applications in modeling the elution behavior of polymers in size exclusion chromatography has been done. And the research focused on the effect of semi-flexible of polymer chain, the volume exclusion effect of different chain unit and polymer conformation on the elution behavior in size exclusion chromatography.Based on this, we used different molecular models(the wormlike chain model, the all atom model, Kremer-Grest model) and computer simulation algorithms(traditional Monte Carlo simulation, PERM algorithm of Monte Carlo, molecular dynamics simulation and Langevin simulation) to study the following four aspects:(1) The separation mechanism of polymer in confined space, i. e. what size of the separation of polymer in SEC is based on?(2) The relationship between size and molecular weight of polystyrene standards in a good solvent(3) Characterizing geometric properties of porous materials in chromatographic column with the method of inverse-size exclusion chromatography.(4) The dependence between size and polymer conformation of cyclic polymers in a good solvent. The conclusions are as follows:(1) In the range of 0.1 ≤ K ≤ 0.9, there is a good correlation between K and <X> or(Rg<X>)0.5 of semi-flexible polymer chain contains the volume exclusion effect in confined space, and K is partition coefficient of polymer in SEC, <X> is the mean span of polymer. In other words, polymer chains with different flexibility will have a most same partition coefficient in a confined cylindrical pore if they have the same <X> or, more precisely,(Rg<X>)0.5.(2) Relationships between <X>, Rg, <X>/Rg and M of polystyrene in a good solvent has been obtained, respectively. With these results, the <X> can be got easily if the molecular weight M or the root mean square radius of gyration Rg is known.(3) An almost universal formula of elution volume, Ve was developed. And the size information of chromatographic column packing has been obtained with the method of non-linear fitting.(4) Sizes and branching index of four different cyclic polymers have been obtained with the help of coarse-grained Kremer-Grest model and Langevin dynamics simulation. Combing the branching index and the second part results of linear polystyrene, sizes of cyclic polystyrene in good solvent can be further obtained, which laid the foundation for the prediction of the elution behavior of cyclic polymers.