INTRAMOLECULAR EXCIMER FORMATION IN MODEL COMPOUNDS FOR POLYESTERS PREPARED FROM 2,6-NAPHTHALENE DICARBOXYLIC-ACID AND 8 DIFFERENT GLYCOLS

Fluorescence has been measured in dilute solutions of model compounds for polymers of 2,6-naphthalene dicarboxylic acid and eight different glycols. The glycols are HO-(CH2)i-OH, i = 2-6, and H-(OCH2CH2)j-OH, j = 1-4. The ratio of excimer to monomer emission depends on the glycol used. Studies as functions of temperature and solvent show that, in contrast with the analogous polyesters in which the naphthalene moiety is replaced with a benzene ring, there can be a substantial dynamic component to the excimer emission. Extrapolation to media of infinite viscosity shows that in the absence of rotational isomerism during the lifetime of the singlet excited state, there is an odd-even effect in the series in which the flexible spacers differ in the number of methylene units, but not in the series in which the flexible spacers differ in the number of oxyethylene units. © 1990.