Synthetic control of cageetwork ratio of poly(methylsilsesquioxane)s for storage stability, hardness, and weather resistance of coating films

摘要

Poly(methylsilsesquioxane) (PMSQ) was synthesized using a two-step process consisting of hydrolysis of methyl trimethoxysilane (MTMS) with aluminum chelate catalyst and successive condensation reactions conducted at elevated temperatures. Results of nuclear magnetic resonance and Fourier transform infrared measurements show that all terminal functional groups were Si=OH in PMSQ. Results show further that PMSQ has both a cage structure and a network structure, and a cageetwork ratio is represented by a height ratio of -64.5/-66.6 ppm. PMSQ of different molecular weight but the same Si=OH concentration is obtainable by varying the condensation reaction conditions such as the concentration, temperature, amount of aluminum chelate catalyst, and the solvent solubility parameter. A difference of the cageetwork ratio occurs. A different cageetwork ratio is dependent on the different reactivities of the intramolecular and intermolecular reactions. The relations of molecular structure of the obtained PMSQ molecular structure were characterized along with functions of storage stability, film hardness, and weather resistance. PMSQ designed with a larger cageetwork ratio is necessary to obtain PMSQ with good storage stability and a coating film having good weather resistance. PMSQ designed with a smaller cageetwork ratio should be prepared to obtain a coating film with high hardness.