Intramolecular excimer formation in macromolecules. II. Energy migration and excimer formation in acenaphthylene-methyl methacrylate copolymers

TLDR: In this paper, ancenaphthylene and methyl methacrylate copolymers of content varying over the total composition range were studied and the extent of energy migration was determined by the mole fraction of aromatic chromophore fa.

Abstract: Excimer formation has been studied in a series of ancenaphthylene—methyl methacrylate copolymers of content varying over the total composition range. In accord with a previous model [Reid and Soutar, J. Polym. Sci. Polym. Lett. Ed., 15, 153 (1977)], the excimer formation has been described by a composite function representative of energy migration and excimer site concentration. In tramolecular energy migration in glassy solutions of the polymers was characterized by use of fluorescence depolarization measurements. The extent of energy migration in the acenaphthylene copolymers is determined by the mole fraction of aromatic chromophore fa. A function Σ descriptive of the excimer site concentration has been generated on the assumption that excimer formation results predominantly from next- to nearest-neighbor interactions. Σ is based upon the pentad distribution of aromatic chromophores in the chain and contains pentad fractions appropriately weighted according to the frequency and relative importance of their potential excimer sites. Reactivity ratios of acenaphthylene and methyl methacrylate in copolymerization at 70°C were ra = 0.80 and rm = 0.57.