(1) a repeating unit having the formula (1): ##STR1## in which R11 is the hydrogen atom or an alkyl group containing 1-6 carbon atoms; Q1 is --COO--, --CON(R11)--, or an arylene group containing 6-10 carbon atoms; L1 is a divalent group containing at least one linkage selected from the group consisting of --COO-- and --CON(R11)-- and containing 3-15 carbon atoms, or a divalent atom containing at l