EFFECT OF TEMPERATURE AND SOLVENT ON THE CYCLIZATION OF A POLYSTYRENE CHAIN

Cyclization rate measurements were carried out on a polystyrene chain (M(n) = 4500; M(w)/M(n) = 1.08, both ends labeled with 1-pyrenyl groups) in toluene, cyclopentane, cyclohexane, and methylcyclohexane, between 22 and 95-degrees-C. The solvent-polymer interaction energy changes with temperature, influencing both excluded volume effects, chain flexibility, and hydrodynamic properties of the chain. Excluded volume effects suppress the chain end pair distribution function for short distances, retarding the cyclization rate constant and accelerating the ring opening process. However, excluded volume effects alone are not able to explain all aspects of the cyclization process. It is necessary to invoke the variation of chain flexibility and hydrodynamic properties of the polymer chain with temperature.