Model polyisoprenes with associating end-groups

Abstract

A series of narrow distribution ω-functionalized linear polyisoprenes were prepared by converting the tertiary amine group of polyisoprene - obtained by anionic polymerization of isoprene with 3-(dimethylamino)propyl lithium - to the highly polar sulfo-zwitterion group by treatment with cyclopropane sultone. The dilute solution properties of these polymers were mainly examined in cyclohexane and cyclohexane/1-heptanol mixtures. In cyclohexane the sulfo-zwitterion polymers were highly aggregated. The degree of association generally decreases with increasing base chain length, due to excluded volume repulsions of the polymeric tails, except at very low molecular weights (2 400–4 800) where the different microstructure of these polymers may play a role. Depending on the molecular weight of the linear precursor, the aggregates may resemble star polymers or may exhibit a more extended core morphology. These findings, regarding the shape of the aggregates, are also supported by melt viscosity mesurements and x-ray scattering studies.