VISCOELASTIC PROPERTIES OF TELECHELIC IONOMERS .2. QUATERNIZED ALPHA,OMEGA-BIS(DIMETHYLAMINO)POLYISOPRENE

A short-length polyisoprene (MBAR(n) = 5000) was selectively end-capped at both ends by a dimethylamino group. Quaternization of these end groups by a series of n-alkyl iodides deeply affected the dynamic mechanical behavior. The glass transition temperature (T(g)) of polyisoprene and the storage modulus (G') in the glassy state were found to be largely dependent on the length of the n-alkyl group of the quaternization agent: both of these properties increased as the n-alkyl group was shortened. Furthermore, as a result of the quaternization of the tertiary amine end groups a rubbery plateau emerged in the isochronous curves of G' vs temperature. An ionic relaxation peak was also displayed by the thermal dependence of the loss modulus (G"), in a range depending on the length of the n-alkyl group and on the functionality of the quaternization agent.