TRIPLET PROBE STUDY OF COLLISION RATES OF SMALL MOLECULES WITH CHAIN TERMINAL AND CENTRAL GROUPS OF POLYSTYRENE

To study the mechanism of collision rates between small molecules and polymers, the rate constants k for quenching of phosphorescence of benzil by a terminal or central anthryl group attached to polystyrene (degree of polymerization, P=25—10, 000) have been measured in benzene, butanone, and cyclohexane at 20—40°C by using a 10 ns dye laser pulse. The reduced rate constant kη/T for quenching of benzil by a terminal anthryl group of polystyrylanthracene decreases to 1/2—1/3 of that for quenching of benzil by 9-methylanthracene. No difference in kη/T due to the difference in solvent was observed for this case. The curve of kη/T for quenching of benzil by the central anthryl group of PS–A–PS against P shows an additional decrease in kη/T for P>10. This decrease is more marked in poor solvents than in a good solvent. These results are explained consistently by considering the obstructive effect of polymer segments on the diffusion of the reacting benzil molecule through the polymer coil. © 1979, The Society of Polymer Science, Japan. All rights reserved.