1-heptene, 3-heptenes and cumene as model compounds of SBS block copolymers. Study of their photoreactions in the presence of photoinitiators of polymerization

Abstract

The photoreactions of 1-heptene, 3-heptene and cumene in the presence of unimolecular and bimolecular reaction photoinitiators (1,1-dimethoxy-1-phenyl-acetophenone, DMPA, and benzophenone, BP) has been investigated. Quantum yields of the reactions and identification of the photoreaction products has permitted to elucidate the steps and the mechanism of the mentioned photoreactions. This helps to know the reactions which take place in more complicated systems, such is the case of the photopolymerization of acrylic monomers in SBS block copolymer matrices, of which these compounds could serve as models. For heptene derivatives, the photoreaction in the presence of BP takes place through direct abstraction of an allylic hydrogen atom, and in minor extension, of other hydrogen atoms of the heptene aliphatic chain. As the main form of termination, the heptenyl and the ketyl radicals formed coupled inside the solvent cage. Photoreaction in the presence of DMPA occurs by direct attack of the radicals formed from the initiator (PhCO ∗, Ph(MeO) 2C ∗, and CH 3 ∗ to the heptene double bond. When this double bond is terminal oligomerization occurs. For cumene, the photoreaction takes place through direct abstraction of the benzylic hydrogen atom both cases.