ANIONIC POLYMERIZATION OF STYRENE EFFECT OF TETRAHYDROFURAN

Abstract

The propagation step in the butyllithium­initiated polymerization of styrene in benzene solution is thought to be due to a small concentration of highly active free ion-pairs in equilibrium with unreactive dimeric ion­pairs. This work shows that these dimers may be broken down by the addition of tetrahydrofuran. Small quantities of tetrahydrofuran form, first, a low concentration of a monoetherate of the ion­pair with a high reactivity, and this augments the propagation reaction without changing the kinetic order with respect to the initiator. This, at higher tetrahydrofuran concentrations, is followed by the complete breakdown of the dimers to give a dietherate in much higher concentration and lower reactivity compared with the initial ion­pair and monoetherate. The kinetic order with respect to the initial initiator species changes from one half to one during this process, and a maximum appears in the rate as the ether concentration increases.