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

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 (SiO 2 ), were investigated using molecular dynamic simulation. The results indicate that binding energy between PI molecules and SiO 2 surface mainly comes from van der Waals interaction. Proper silane coupling agents generate a thin membrane on the surface of SiO 2 , which improves the thickness of the transition layer between PI molecules and SiO 2 surface. And density of the transition layer was enhanced by APTES significantly. In addition, amino group (NH 2 ) improves the electrostatic interaction between PI molecules and SiO 2 surface rather than epoxy group (CHCH 2 O) and methacrylic oxide group (OCOC(CH 3 )CH 2 ). As a result, APTES enhances the binding energy effectively. However, excessive silane coupling agent increases the distance between PI matrices and SiO 2 , which deteriorates performance of the interface. In addition, GOTMS and MPTS generate a thick and dense membrane on SiO 2 surface, which induces the loose transition layer and poor binding energy. Overlap parameter between PI molecules and SiO 2 surface grafted with silane coupling agent can be employed to evaluate the transition layer successfully.