Molecular weight dependence of magnetic circular dichroism for polystyrenes in solution

Abstract

The molecular weight dependence of the magnetic circular dichroism (MCD) for polystyrenes (PS) has been studied in various solvents by using the normalized dipole-strength D*. The normalized MCD intensity B* is not so much affected by the molecular weight as the normalized dipole strength D*. The ratio of the Faraday parameter to the dipole strength, B*/D*, decreases as the molecular weight increases to 4,O. lo3 and is constant above it. The increase of the normalized D* with the increase of molecular weight is interpreted in terms of the closer approach of chromophores. These results indicate that MCD for polystyrenes is influenced by the interaction of chromophores in a polymer chain; the decrease of E*/D* comes from the increase of the interaction of chromophores. This tendency is enhanced by solvent effects on MCD.

Interpretation of the excimer kinetics of poly(N-vinylcarbazole) and 1,3-dicarbazolylpropane in dilute solutions

“…Once again, this dissociation process, although small, cannot be ignored. 4 If the analysis is carried out including the second term on the right-hand side of eq 6, the fluorescence decay curves of either excimer obey a linear combination of three exponentials with relaxation rates 1/rj = Mn where kA. = kFA.…”

Singlet Electronic Energy Transfer in Polymers Containing Naphthalene and Anthracene Chromophores

“…With the development of improved methods of measurement of nanosecond fluorescence lifetimes,4'3 transient measurements have been applied to analysis of the kinetics of excimer formation. [6][7][8][9][10][11][12][13][14][15] In all studies of homopolymers of naphthalene-containing monomers, the fluorescence decay function of the monomeric chromophore was not a single exponen-tial8,11,14'13 but could be represented adequately by a sum of two exponential decays. Because it generates decay laws of this functional form, the starting point for the interpretation of excimer kinetics in polymeric systems usually is a mechanism incorporating formation and subsequent dissociation of an excimer, as shown in Scheme I.…”