Investigation of the microphase separation in blends of polyurethane-basedionomers

Blends of an anion containing polyurethane (PU1) and polyaminourethane (PU2 ) were investigated. Dielectric relaxation spectroscopy (DRS), differential scanning calorimetry (DSC), and small-angle X-ray scattering (SAXS) were u sed in a study of the molecular mobility and microphase morphology and thei r dependence on the composition of these ionomers. Dielectric thermally sti mulated depolarization current (TSDC) measurements of the ionomer blends sh owed four relaxation mechanisms. The subglass secondary gamma- and beta-rel axations are related to local motions; the alpha-relaxation is related to t he glass transition of the amorphous soft phase of the ionomers, and the Ma xwell-Wagner-Sillars (MWS) relaxation is related to interfacial polarizatio n caused by the motion of ions released during the glass transition. The al pha- and MWS TSDC relaxations are strongly affected by the degree of microp hase segregation (DMS) of the ionomer blends. Based on TSDC measurements, t he parameter m(TSDC), a criterion expressing a relative degree of phase mix ing, is introduced. According to this parameter, the classification of the investigated ionomer blends, in order of decreasing phase mixing (PU1/PU2 i n %) is 50/50 (mixed) > 0/100 > 5/95 > 10/90 > 100/0 > 30/70 (high separati on). It appears that, as a result of the complexity of the systems, their s tructures and their properties are not simple functions of their compositio n. SAXS measurements show that pure PU1 ionomer has a high degree of microp hase separation. The introduction of PU2 in the blend causes defects in the hard domains and leads to a structure with mixing of the soft and hard mic rophases. SAXS measurements concerning DMS are in good agreement with the T SDC results and support the introduced criterion of the relative degree of phase mixing.