Photopolymerization quantum yields in two reactive diacetylenes, 3BCMU and 4BCMU, and relation to γ-ray induced polymerization

Photopolymerization initiation yields from neutral excited states ηi are measured; for 4BCMU, ηi ≈ 0.075, but this value is 200 times smaller for 3BCMU, although the γ-ray reactivities of the two materials are similar. This difference is not related to different geometries of the reaction centre. It is proposed that it is due to different strengths of hydrogen bonds between side groups. The importance of ionic initiation under γ-ray irradiation is discussed.