Polycyanurate networks modified by polyoxytetramethylene glycol

Summary We report results obtained within a collaborative project dealing with the preparation of hybrid polycyanurate/polyoxytetramethylene glycol (PCN/PTMG) networks and the investigation of their structure-property relationships by a variety of experimental techniques. The hybrids were prepared from PCN and PTMG (molar mass 1.000 g/mol) with 10, 20, 30 and 40 wt% PTMG. The degree of incorporation of PTMG into the PCN network was determined by gel fraction measurements. WAXS and SAXS studies had indicated that the materials under investigation are amorphous and exhibit nanostructural heterogeneity, which increases with increasing amount of PTMG. Stress-strain measurements show improvement of the mechanical properties for PTMG contents of 30 and 40%. The focus in this paper is on the detailed investigation of the α relaxation associated with the glass transition in wide ranges of frequency and temperature by dielectric techniques. A single α relaxation was observed in all the compositions shifting systematically to lower temperatures/higher frequencies with increasing PTMG content. The results were systematically analyzed in terms of time scale and relaxation strength of the response and are discussed in terms of plasticization, presence of nanostructural heterogeneities and hybridization. Co-operativity of the α relaxation, quantified in terms of fragility, was found to decrease with increasing amount of PTMG, in correlation with increasing level of nanoheterogenity.