A material for use in forming organic semiconductor, charge transporting or light emitting polymers comprising: a photopolymerizable material having the molecular structure B-S-A-S-B, characterised in that B is a crosslinkable end group; S is a flexible spacer; and A is an aromatic molecular nucleus having the structure -(Ar-D) n- Ar- wherein n = 1 to 6; Ar is an aromatic diradical, a heteroaromatic diradical bonded linearly to adjoining diradicals, or a single bond; wherein D are each independently chosen from the group: or and wherein X is independently selected from N, CH, or CR 1 where R 1 is independently selected from hydrocarbyl groups, C j H 2j+1, branched hydrocarbyl groups, or hydrocarbyl groups with one or more heteroatoms of S, N, O, P, or Si with j = 1 to 6; and R is independently selected from hydrocarbyl groups, C m H 2m+1, branched hydrocarbyl groups, or hydrocarbyl groups with one or more heteroatoms of S, N, O, P, or Si, with m = 1 to 15, and the Ar and D diradicals are independently selected in each of the n subunits of the aromatic molecular nucleus A. B is a crosslinkable end group; S is a flexible spacer; and A is an aromatic molecular nucleus having the structure -(Ar-D) n- Ar- wherein n = 1 to 6; Ar is an aromatic diradical, a heteroaromatic diradical bonded linearly to adjoining diradicals, or a single bond; wherein D are each independently chosen from the group: or and wherein X is independently selected from N, CH, or CR 1 where R 1 is independently selected from hydrocarbyl groups, C j H 2j+1, branched hydrocarbyl groups, or hydrocarbyl groups with one or more heteroatoms of S, N, O, P, or Si with j = 1 to 6; and R is independently selected from hydrocarbyl groups, C m H 2m+1, branched hydrocarbyl groups, or hydrocarbyl groups with one or more heteroatoms of S, N, O, P, or Si, with m = 1 to 15, and the Ar and D diradicals are independently selected in each of the n subunits of the aromatic molecular nucleus A. n = 1 to 6; Ar is an aromatic diradical, a heteroaromatic diradical bonded linearly to adjoining diradicals, or a single bond; wherein D are each independently chosen from the group: or and wherein X is independently selected from N, CH, or CR 1 where R 1 is independently selected from hydrocarbyl groups, C j H 2j+1, branched hydrocarbyl groups, or hydrocarbyl groups with one or more heteroatoms of S, N, O, P, or Si with j = 1 to 6; and R is independently selected from hydrocarbyl groups, C m H 2m+1, branched hydrocarbyl groups, or hydrocarbyl groups with one or more heteroatoms of S, N, O, P, or Si, with m = 1 to 15, and the Ar and D diradicals are independently selected in each of the n subunits of the aromatic molecular nucleus A. X is independently selected from N, CH, or CR 1 where R 1 is independently selected from hydrocarbyl groups, C j H 2j+1, branched hydrocarbyl groups, or hydrocarbyl groups with one or more heteroatoms of S, N, O, P, or Si with j = 1 to 6; and R is independently selected from hydrocarbyl groups, C m H 2m+1, branched hydrocarbyl groups, or hydrocarbyl groups with one or more heteroatoms of S, N, O, P, or Si, with m = 1 to 15, and the Ar and D diradicals are independently selected in each of the n subunits of the aromatic molecular nucleus A.