Intramolecular Complex Formation and Triplet Energy Transfer in Polynorbornenes Incorporating Benzophenone

The photophysical properties of homopolymers ( 2 ) and block copolymers ( 3 ) prepared by ring-opening metathesis polymerization of norbornenes substituted with benzophenone, naphthalene, and phenanthrene groups ( 1 ) have been investigated. When benzophenone is attached to this polynorbornene backbone, its excited state behavior differs from that observed for monomeric benzophenone. A new intramolecular excited state complex can be observed in the transient absorption and emission measurements of the benzophenone-substituted homopolymer. In copolymers bearing benzophenone and naphthalene or phenanthrene substituent blocks, triplet energy transfer from the sensitizer (benzophenone) to the arene is observed. This energy transfer dominates over the intramolecular complexation that characterizes group interactions in the homopolymer.