Polymer Cyclization

My first entry into polymer science was the study of end-to-end cyclization of polymers. We prepared polymers of narrow molar mass distribution with pyrene groups on both ends, and used time-resolved fluorescence methods to study the kinetics of intramolecular excimer formation. This project continued over more than a decade, and examined the influence of solvent, polymer structure, unlabeled polymer concentration, and other factors on the cyclization rate and cyclization probability of these polymers. [see Accounts Chem. Res., 18, 73-79 (1985)] Our two most important contributions were the demonstration of the large influence of excluded volume effects on polymer cyclization, and the determination of the power law exponents (in good and theta solvents) in the chain-length dependence of the cyclization rate. [see J. Amer. Chem. Soc., 107, 5798-5800 (1985)] Our last effort in this area [see Macromolecules, 30, 2633-2641 (1997)] looked at cyclization of two points in the polymer interior. We prepared a series of polymers with two pyrenes separated by a common PEO chain with tails of varying length, and compared chain dynamics of interior segments of the polymer with that of segments at the chain ends.