Small-Angle X-ray Scattering and Small-Angle Neutron Scattering Studies of Liquid-Crystalline Halato(semi)telechelic Polymers

Model liquid-crystalline ionomers have been synthesized, which consist of low molecular weight (700–49 000) linear ω- and α,ω-sodium sulfonato- and carboxylato-poly(styrenes or isoprenes) selectively end-capped at one or both end(s) with an ionic mesogenic group. These compounds are referred to as liquid-crystalline halato(semi)telechelic polymers [LC H(S)TPs]. A combination of small-angle X-ray scattering and small-angle neutron scattering studies on these LC H(S)TPs clearly shows the usual ionic peak related to interparticle interference between the ionic aggregates and a peak which can be related to the organization of a smectic mesophase. This mesogenic peak is generally masked by the foot of the broad ionic peak. The ionic peak Bragg spacing is much larger in the LC H(S)TP than in the H(S)TP precursor. This increased interaggregate distance results from the hindrance due to the mesogenic organization and from the restricted mobility experienced by the chains closely attached to the mesogen layers. As a rule, the lower the glass transition temperature of the polymeric matrix, the better the definition of the ionic peak. The ionic peak is well defined as long as the temperature is lower than the temperature of transition from solid to smectic phase (323 K). At higher temperatures, the ionic peak intensity decreases with increasing temperature.