ACID BASE-INDUCED ASSOCIATION OF AMINO-TERMINATED POLYSTYRENES .1. LINEAR-CHAINS AND RING FORMATION

The associating coupling process of tertiary-amino-terminated polystyrene (PS) chains with monofunctional and bifunctional dinitrophenol reagents has been studied by means of UV-vis spectroscopy and light-scattering measurements as a function of polymer concentration. The mechanism of coupling was first checked with monofunctional PS chains. The equilibrium constants of the two functional groups of the coupler were found to be slightly different from each other; but with the same average value as for the monofunctional phenol compound. The increase of molecular weight agreed well with predictions from Flory's theory. Much smaller weight average molecular weights were found, however, for the coupling of telechelic PS chains, and the deviations are stronger for the short chains than for the longer ones. The effect is explained by ring formation and three approximations were applied. These are (a) a mean field approximation, (b) the Jacobson-Stockmayer (JS) approach, and (c) the JS approach including excluded volume effect and its influence on Gaussian statistics. Molecular weights were also calculated from the weight fraction of rings and fitted to those obtained by LS where the effective bond length b was chosen to be the adjustable parameter. In the original JS treatment the effective bond length increased with the chain length of the primary chain. In treatment c this could be eliminated by consideration of excluded volume, but absolute values of b are unrealistically low.