Influence of Thermal History on Microphase Separation and Morphology of Elastomeric Polyureas

Polyureas are versatile elastomers consisting of alternating soft and hard segments. These polymers tend to form a nanophase-segregated morphology consisting of high aspect ratio hard domain ribbons in a low Tg matrix, the details of which are key in tailoring the unique characteristics of this family of materials. In the present work, bulk-polymerized polyureas were synthesized from a modified diphenylmethane diisocyanate and a polytetramethyleneoxide based diamine (1000 g/mol) and annealed at selected elevated temperatures. Various experimental probes (e.g. atomic force microscopy and small-angle X-ray scattering) reveal significant changes in hard domain ordering as a function of thermal history. Time-resolved synchrotron X-ray scattering was also conducted as a function of temperature to augment these findings.