PURPOSE: To provide an allylic oligomer useful as the material of an org. glass which has a higher refractive index than that of conventional org. glasses and is suitable for a high-impact optical material.
CONSTITUTION: An allylic oligomer of the formula: CH 2 =CHCH 2 O(COACOOR 1 SR 2 O) n COACOOCH 2 CH=CH 2 [wherein A is an org. group derived from a dicarboxylic acid; R 1 and R 2 are each a divalent org. group derived from a 2-10C aliph. hydrocarbon; and n is 1-20] contg. sulfur atoms is used as the material of an org. glass.