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Combined Effects of Carbonate and Soft-Segment Molecular Structures on the Nanophase Separation and Properties of Segmented Polyhydroxyurethane
journal contribution
posted on 2017-04-13, 17:21 authored by Goliath Beniah, Xi Chen, Brice E. Uno, Kun Liu, Emily K. Leitsch, Junho Jeon, William H. Heath, Karl A. Scheidt, John M. TorkelsonThe influence of
hard-segment structure on the properties of segmented
polyhydroxyurethane (PHU) was investigated using three bis-carbonate
molecules: divinylbenzene dicyclocarbonate (DVBDCC), Bisphenol
A dicarbonate (BPADC), and resorcinol bis-carbonate (RBC). These carbonates
were formulated with poly(tetramethylene oxide) (PTMO)-based and polybutadiene-co-acrylonitrile (PBN)-based soft segments at 40 wt % hard-segment
content, resulting in non-isocyanate polyurethanes (NIPUs). Small-angle
X-ray scattering, dynamic mechanical analysis, and tensile testing
reveal that hard-segment and soft-segment structures may cooperatively
influence segmented PHU properties. With PTMO-based soft segment,
BPADC yields phase-mixed PHU because of strong intersegmental hydrogen
bonding from the hard-segment hydroxyl groups to the soft segment;
in contrast, because of moderate intersegmental hydrogen bonding to
the PTMO-based soft segment, DVBDCC and RBC lead to nanophase-separated
PHUs with 15–17 nm interdomain spacings with substantial, broad
interphase regions and low tensile strengths of ∼0.40 MPa for
DVBDCC and ∼0.27 MPa for RBC. By suppressing intersegmental
hydrogen bonding via the use of PBN-based soft segment, formulations
with all three carbonate molecules lead to nanophase-separated PHUs
with interdomain spacings of 11–16 nm, narrow interfaces, and
improved tensile strengths ranging from 1.6 to 0.5 MPa in the order
DVBDCC > BPADC > RBC. All PBN-based PHUs exhibit reversibility
of
extension with hysteresis similar to that found in thermoplastic polyurethane
elastomers.