Interface of polyimide–silica grafted with different silane coupling agents: Molecular dynamic simulation

ABSTRACT In this article, the effects of different silane coupling agents: 3‐glycidyloxypropyltrimethoxysilane (GOTMS), 3‐aminopropyltriethoxysilane (APTES), and 3‐methacryloxypropyltrimethoxysilane (MPTS), on the interface between polyimide (PI) and silica (SiO2), were investigated using molecular dynamic simulation. The results indicate that binding energy between PI molecules and SiO2 surface mainly comes from van der Waals interaction. Proper silane coupling agents generate a thin membrane on the surface of SiO2, which improves the thickness of the transition layer between PI molecules and SiO2 surface. And density of the transition layer was enhanced by APTES significantly. In addition, amino group (NH2) improves the electrostatic interaction between PI molecules and SiO2 surface rather than epoxy group (CHCH2O) and methacrylic oxide group (OCOC(CH3)CH2). As a result, APTES enhances the binding energy effectively. However, excessive silane coupling agent increases the distance between PI matrices and SiO2, which deteriorates performance of the interface. In addition, GOTMS and MPTS generate a thick and dense membrane on SiO2 surface, which induces the loose transition layer and poor binding energy. Overlap parameter between PI molecules and SiO2 surface grafted with silane coupling agent can be employed to evaluate the transition layer successfully. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45725.