Ultraviolet Absorption and Fluorescence Emission Spectroscopic Studies of Macrocyclic and Linear Poly(9,9-dimethyl-2-vinylfluorene). Evidence for Ground-State Chromophore Interactions

Abstract

UV absorptivities of macrocyclic and matching linear poly(9,9-dimethyl-2-vinylfluorene) prepared from the same precursors show decreases of 30 and 15%, respectively, as degrees of polymerization (DPn's) increase from 12 to 142. The strong increase in hypochromism with molecular weight for the macrocycles indicates an increase in ordering of the large pendent aromatic chromophores. The emission intensities of the low-DPn macrocycles were found to be enhanced up to 20% compared to the matching linear polymers. This is attributed to both decreased excimer formation and lower rates of radiation-less decay especially in the smaller rings.