Polymeric photoinitiators of the formula I or II wherein n and m independently of one another are 3-5; o is 10-16; p is 4-8; R is phenyl-CO--CO--O--; Y and Y' independently of one another are C.sub.1-C.sub.10alkylene or --[(CH.sub.2).sub.a--O--(CH.sub.2).sub.b].sub.c-- wherein a is 2-10, b is 0-10, c is 1-3; with the proviso that they are, however, at least 1 if the methylene group in question is between two oxygen atoms.