The effect of Trimethylchlorosilane as a reactive additive on solution behavior of polyamide acid and properties of corresponding polyimide

Trimethylchlorosilane (TMSCL) with different volume ratios was added to polyamide acid (PAA) solutions which were obtained by polymerization of Pyromellitic dianhydride (PMDA) and 4, 4'-Oxydianiline (ODA) in N-methyl-2-pyrrolidone (NMP) solvent. With the addition of TMSCL, the apparent viscosity of PAA solutions shows a sharp fall ranging from 137.6x10(4) to 1.0x10(4) cP with a substantial decline up to about 99 %. Gel permeation chromatography (GPC) measurements indicate that the molecular weights change little with the different addition ratios of TMSCL. The results of X-ray photoelectron (XPS) and Fourier Transform Infrared (FTIR) show that TMSCL reacts with carboxyl groups of PAAs to form silicon ester bonds, which results in two aspects of positive effects. For one hand, the consuming of carboxyl groups weakens the intensity of inter-chain hydrogen bonds among macromolecules, which leads to a sharp fall in apparent viscosity of PAA solutions. For the other hand, as carboxyl groups were consumed, the decomposition in a rational way of hydrolysis and exchange reactions catalyzed by carboxyl groups is prevented. Therefore the storage stability of PAA solution is also improved. The results of X-ray diffraction (XRD) show that the mean intermolecular distance of PAA chains increases with increase in TMSCL, which farther confirms the intensity of interchain hydrogen bonds among macromolecules decreases with the addition of TMSCL. The results of mechanical properties measurements, thermo gravimetric analysis (TGA) and dynamic mechanical analysis (DMA) indicate that the outstanding mechanical and thermal properties of polyimide films corresponding to PAA with TMSCL were still maintained well.