Photophysical Processes in Polymers. IV. Excimer Formation in Vinylaromatic Polymers and Copolymers

Abstract

Excimer formation has been investigated in polystyrene, poly(1‐vinylnaphthalene), poly(2‐vinylnaphthalene), and in copolymers of 1‐vinylnaphthalene with styrene and with methyl methacrylate. Solid films as well as solutions were studied over the temperature range 77–298°K. In the solidpolymers, interchain excimer formation is superimposed on the intrachain interaction observed in dilute solutions; intrachain excimer formation is essentially unaffected by the solvent in fluid solutions. Conformations that lead to excimer interaction in a solid solution are fixed by the temperature at which the solid is formed. Activation energies for intramolecular excimer formation for these polymers are somewhat less than those for the corresponding two‐unit model compounds and much less than those for the single‐unit model compounds. While excimer sites act as efficient singlet traps for intramolecularly migrating energy and act to decrease the triplet yield, they do not present a barrier to the transfer of energy to a deep trap within the polymer chain.