yamide acid having organopolysiloxane side chain with repeating units shown by the formulas VIII and IX ##STR22## in which R8 is an alkyl group, A1 is a tetravalent aromatic group, A3 is a divalent aromatic group and A2 is a divalent organic group shown by the formula V below, ##STR23## in which Z and m have their previously defined meanings, the molar ratio of repeating unit VIII to repeating uni