"(wherein 100 to 50 mol % of A stands for defined mesogenic group, 0 to 50 mole % of A is p-phenylene, m-phenylene or trans-1,4-cyclohexylene, B is a defined spacer group, and X is ester bond, carbonate bond, amide bond, urethane bond or urea bond, and a repeating unit of the formula:" . . . .