side chains produced by irradiation of light, and having a repeating unit derived from a diacetylene monomer of the formula: Ra--C.tbd.C--C.tbd.C--Rb where Ra and Rb are respectively -X-Y-Z, wherein X is a spacer group --(CH2)n --, --(Cm H2m--2)--, --(Cm H2m--4)--, --(Cp H2p O)--, or --(Cp H2p--2 O)--, n is an integer equal to 1 or more, m is an integer from 2 to 12, and p is an integer from 1 to