PURPOSE: To obtain a skin model membrane showing improved functions as a skin-like membrane when subjected to an in vitro examination of the permea tion of a drug through the skin by using a polymer of a specified styrene deriva tive having a long-chain alkyl group.

CONSTITUTION: A reaction product of (chloromethyl)styrene with a dialcoholamine compound is reacted with an aliphatic carboxylic acid chloride at room temperature to 100°C in an organic solvent to obtain a styrene derivative having a long-chain alkyl group and represented by the formula (wherein A is a 2-6C polymethylene chain which may be substituted with a methyl or ethyl group; and m is an integer of 10-30). This derivative is polymerized at 40-100°C in the presence of a radical polymerization initiator in an organic solvent to obtain a polymer having long-chain alkyl groups at the side chain positions. A skin-like model membrane is obtained by forming this polymer into a membrane by e.g. a solvent cast process, a melt molding process or by impregnating or coating a porous membrane with a solution formed by dissolving the polymer in a suitable solvent.