Tuning nanophase separation behavior in segmented polyhydroxyurethane via judicious choice of soft segment

Polyhydroxyurethane (PHU) is of major research interest because it is a non-isocyanate polyurethane-like (NIPU) polymer. Here, we demonstrate the ability to tune nanophase separation in linear, segmented PHU copolymers via the soft segment. PHUs were synthesized from polytetramethylene oxide (PTMO)and polybutadiene-co-acrylonitrile (PBN)-based soft segments, with divinyl benzene dicyclocarbonate and Dytek-A as hard segment and chain extender, respectively. These NIPU polymers were characterized by small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and tensile testing. SAXS reveals that the NIPUs with 30-40 wt% hard segment are nanophase separated with interdomain spacings of 9-16 nm. DMA reveals that PTMO-based PHUs have broad interphases with a range of local compositions and glass transition temperatures (T(g)s), with tan delta >= 0.3 over temperature ranges exceeding 70 degrees C in breadth. In contrast, PBN-based PHUs have sharper interphases, evidenced by narrow tan delta peaks near soft-segment and hard-segment Tgs as well as by DSC and AFM data. FTIR shows that the ratio of hydrogen-bonded carbonyl to free carbonyl is higher in PBN-based PHU than in PTMObased PHU, consistent with the absence and presence of intersegment hydrogen bonding in PBN-based PHU and PTMO-based PHU, respectively. (C) 2017 Elsevier Ltd. All rights reserved.