4.80 g of phenyltrimethoxysilane, 70.71 g of tetraethoxysilane, 17.20 g of methyltriethoxysilane, 0.14 g of trimethoxysilylpropyl succinic anhydride, 5.78 g of mercaptopropyltriethoxysilane, and 150 g of acetone were charged into a 500 ml flask to be dissolved and the resultant mixed solution was warmed while stirring the mixed solution with a magnetic stirrer to reflux. Next, 32.31 g of a 0.01 M hydrochloric acid aqueous solution was added to the mixed solution. The reaction was carried out for 240 minutes and then the resultant reaction solution was cooled down to room temperature. Then, 200 g of propylene glycol monoethyl ether was added to the reaction solution, and ethanol, water and hydrochloric acid being reaction by-products were distilled off under reduced pressure to obtain a hydrolysis-condensation product. To the hydrolysis-condensation product, 1.36 g of a 10% by weight triphenylsulfonium hydroxide aqueous solution was added to obtain a triphenylsulfonium succinic acid salt-containing Si polymer. The obtained polymer corresponded to a polymer having five types of unit structures of Formula (3-31). The molecular weight Mw of the obtained polymer measured by GPC was found to be 1,500 in terms of polystyrene.
