Polymerization of ?-Methylstyrene in Tetrahydrofuran with Potassium as Initiator. II. Gel-Permeation Chromatographic Analyses of Polymers

Publisher Website
Google Scholar
Abstract
Polymerization of α-methylstyrene initiated with potassium and potassium naphthalene in tetrahydrofuran as solvent has been carried out in the temperature range of -78 to 55°C. The type of propagation-whether reversible or irreversible-has been verified in these polymerizations at -78, -25, -5, and 25°C by comparing the gel-permeation chromatographic molecular weight distributions of polymers before and after depropagation. It has been postulated that in the polymerization of a-methylstyrene at 25°C with potassium alone as initiator, the propagation attributed to contact ion-pair mechanism is irreversible in nature. Contribution towards propagation at -25°C where solvent-separated ion-pairs are known to be active has been shown to be completely reversible. It has also been shown that at -78°C, where free ions are most reactive, the propagation may also be irreversible. In the presence of naphthalene in reactions at 25°C, the extent of reversibility has been shown to increase. This has been attributed to the tendency of naphthalene to form coordinate complexes with potassium, which are quite capable of propagating the polymerization reaction thus leaving lesser monomer for the contact ion-pair propagation which is irreversible.

This publication has 11 references indexed in Scilit: