The Study Of Self-assembled Structures And Mechanical Properties Of Polymer Blend Films

Polymer materials, which are formed by blending different kinds of polymer through physical or chemical methods, are regraded as a kind of modified polymer materials with novel performances. The overall properties of such blends can be tailored to exploit the desirable features of the individual components. The research history of polymer materials is more than 100 years. Up to now, the research about the mechanism of blending and application of novel materials are still hot research topics in the research of polymer materials. And it continuously makes new achievements and progress. In recent years, with the wide application of polymer films, self-assembly properties of blend films have attracted more and more attention, and it is widely used in chemical separation of engineering materials, biomedical materials, nano-templates for preparation of materials and so on. Mechanical properties of materials are an important measure indicator of material performance. Therefore, the study of polymer materials is very important. A continuous mesoscopic simulation method, which proceed from the heterogeneous materials and combines the Monte Carlo (MC) method and three-dimensional lattice spring model (LSM), is proposed in this paper to predict the microstructures and mechanical properties of polymer materials.Monte Carlo(MC) simulation is an efficient calculative method to obtain self-assembly structures of polymer blends, it can capture a variety of fine mesostructures. MC simulation is adopted here to investigate the phase separation structures of polymer blends confined in flat plates. Simulation results show that the morphology of the blends can be varied by changing the interaction between neutral wall and polymer blends, blending ratio and film thickness. Several morphologies can be obtained, such as cylindrical structures, hemispherical structures, lamella structures and lamella-cylindrical structures. Our simulation results also have a fair agreement with the experimental observations. The output of MC simulation serves as the input of lattice spring model(LSM).LSM is a numerical method which is adopted from the condensed matter physics. In a way, LSMs have been shown to be algebraically equivalent to simple FEMs, and the calculated results of LSM are in good agreement with the theory of Eshelby. LSMs are particularly are well suited to investigating the mechanical properties in complicated heterogeneous systems. The results of local deformation simulated by LSM show that:the local strain and stress of blend films have close relationship with the tensile direction, blending ratio, mechanical constants of invisudual components. When the tensile direction is perpendicular to the film surface, the strain and stress distribution are similar to the meso-structures. If the tensile direction is parallel to the film surface, the local strain and stress distribution become complex. Different mesoscopic structures can be obtained by adjusting the blending ratio, the varation of blending ratio also results in significant changes of local strain and stress, adjusting the blend ratio is an effective way to achieve the polymer modification and develop new materials with novel applications. The disparity in elastic moduli of the blending components is the main reason to cause the variation in local strain and stress. LSM method can not only investigate the local deformation of materials, but also obtain the global Young's modulus. LSM simulation results can be a good illustration of the local strain and stress around the caves, and it is consistent with the theoretical prediction.LSM method can also be used to predict some other mechanical properties of polymer blend film, such as rupture, stress relaxation, creep and buckling. The strain and stress relations of polymer blends are simulated by combining the probability theory and LSM method. The mechanism of fracture can also be explained by this approach. And we can also get the relationship between the blends film strength, toughness and other characteristics. In simulation, we found that the interfacial toughness of polymer blends has great influence on the strength of materials, which explains the reason that many experiments show that the fracture is more likely to occur in the phase interface in polymer blends. Through the simulation of blend film and porous film, we can also explain the mechanism of wrinkle.These studies will be used in the explaining and improving of mechanical properties of phase-separated blend films.