Investigation of the Structure and Properties of Polyisobutylene-Based Telechelic Ionomers of Narrow Molecular Weight Distribution .1.

The solid state morphology of recently developed sulfonated polyisobutylene (PIB) telechelic ionomers with narrow molecular weight distribution (MWD) (\u3c(M)over bar (w)\u3e/\u3c(M)over bar (n)\u3eapproximate to 1.15) was investigated. A small angle X-ray scattering (SAXS) peak often associated with the aggregation of the ionic species in the bulk, as well as a secondary peak, have been observed in the narrow distribution sulfonated PIE telechelic ionomers for the first time. Ionomers of difunctional and tri-arm architecture at several number average molecular weights (\u3c(M)over bar (n)\u3e) with one of several counterions were investigated and the preparation method was also considered in terms of observed SAXS behavior. Compression-molded films made from these narrow MWD telechelics were examined in detail using SAXS. Primary and secondary peaks were observed in the slit-smeared SAXS profiles up to an \u3c(M)over bar n\u3e of 27 kg/mol. The ratio of the interdomain spacings derived from these peaks (ca. 2:1) suggests cylindrical or lamellar ordering in the morphology in both difunctional and tri-arm ionomers. Pinhole SAXS images showed no azimuthal dependence in the scattering pattern and thus, this ordering is on a local scale. It was found that the counterion has an inconsistent effect on the smeared interdomain spacing associated with the SAXS peak. The smeared interdomain spacings were systematic with respect to architecture and \u3c(M)over bar (n)\u3e for solution cast Cs+ ionomers. The difunctional telechelics exhibited higher smeared interdomain spacings than tri-arms of comparable \u3c(M)over bar (n)\u3e and unlike the compression-molded films, the smeared interdomain spacings of the solution cast Cs+ telechelic ionomers increased systematically with increasing \u3c(M)over bar (n)\u3e. Even a broad MWD (\u3c(M)over bar (w)\u3e/\u3c(M)over bar (n)\u3eapproximate to 1.8) tri-arm telechelic ionomer \u3c(M)over bar (n)\u3e of 20.6 kg/mol exhibited a diffuse primary peak in SAXS when solution-cast. However, it exhibited no peak when compression-molded. (C) 1997 John Wiley & Sons, Inc