LADDER-LIKE LOWER ALKYLPOLYSILSESQUIOXANES AND PROCESS FOR THEIR PREPARATION

摘要

A ladder-like lower alkylpolysilsesquioxane having a repeating unit of formula:

(in which R and R min are the same or different and each represents a lower alkyl group) has the ability to form thin films having good heat resistance when from 15 to 30% by weight of the lower alkylpolysilsesquioxane is constituted by a lower molecular weight portion having a standard polystyrene-reduced molecular weight of 20,000 or less, as measured by gel permeation chromatography. The ladder-like methylpolysilsesquioxane (in which R and R min both represent methyl groups) is prepared by dissolving methyltrichlorosilane in an organic solvent comprising a ketone or an ether, adding water to the solution to hydrolize the methyltrichlorosilane, condensing the hydrolyzate and, if necessary, adjusting the molecular weight distribution to achieve the right proportion of said low molecular weight portion.