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The effect of surface modifier on the interphase structure of polyimide/sio2 composites: atomistic simulationтезисы доклада
- Авторы: Komarov P.V., Mikhailov I.V., Y-T Chiu, S-M Chen
- Сборник: Book of abstract, Russian-French Symposium on Composite Materials, July 10-13, 2012 Saint Peterburg
- Тезисы
- Год издания: 2012
- Место издания: N.N. Semenov Institute of Chemical Physics RAS Москва
- Первая страница: 72
- Последняя страница: 72
- Аннотация: The modification of nanoparticles with surface-grafted polymers is a promising method that makes it possible to manage the properties of polymer nanocomposites. The need to change filler properties is caused by the fact that the physical mixtures of polymers and nanoparticles do not always produce nanocomposites. In immiscible heterogeneous systems, the features of intermolecular interaction (polymer–polymer, polymer–nanoparticles, and nanoparticles–nanoparticles) may cause phase separation, which inevitably results in the deterioration of the properties of the composite as a whole. When a surface modifier is used, the thickness of the transition layer can be several orders of magnitude larger than that for unmodified nanoparticles depending on the surface density of the modifier, its molecular weight, and its compatibility with the matrix. In general, the issues associated with the formation of an interface between the polymer matrix and the modified nanoparticles have been less investigated. Theoretical studies of the properties of the interface between the polymer matrix and surface-modified nanoparticles encounter a lot of problems which are caused by the need to take into account many parameters simultaneously. Nevertheless, the large body of facts accumulated recently makes it possible to consider the problem of studying ultrathin polymer films in a direct connection with the research of nanocomposite materials. This analogy is explained by the large contribution of the matrix located in the range of surface forces in the case of both ultrathin films and filled polymers. In this work, we studied the effect of the surface density and molecular weight of a modifier on the properties of a polymer–nanoparticle interface in the frame of atomistic simulation. The model of polyimide–SiO2 nanocomposite was constructed as alternate layers of polymer matrix and inorganic substrate, which may be considered on account of the above analogy. As a matrix we used a polyimide obtained from two monomers: 3,3',4,4'-biphenyltetracarboxylic dianhydride and 1,3-bis(4-aminophenoxy) benzene. For the sake of simplicity, the model of the substrate was built assuming a unit cell of silicon dioxide (in the crystalline form of β-cristobalite) as an infinite layer. Alkylsilyl molecules and hydroxyl groups were used as surface modifiers. The main parameters of our model were i) the molecular weight of alkylsilyl; and ii) the surface grafting density. All simulations were performed by the method of atomistic molecular dynamics using the DL POLY package. The obtained results show that the interface between the polymer matrix and the modified SiO2 surface forms due to the mutual diffusion of the polymer matrix and molecules grafted onto the nanoparticle surface. Upon an increase in the surface density and the weight of the modifier molecules, they can form a separate phase on the surface of the nanoparticles. This indirectly evidences that the aggregation of nanoparticles can occur during the melting–solidification of the material if the molecules of the modifier and polymer matrix are incompatible. http://www.spsl.nsc.ru/FullText/konfe/composites%202012.pdf
- Добавил в систему: Комаров Павел Вячеславович