Thermoplastic polyhydroxyurethanes (PHUs) were synthesized from cyclic carbonate aminolysis. Because of the hydroxyl groups in PHU, the choice of soft segment has a dramatic influence on nanophase separation in polyether-based PHUs. Use of a polyethylene glycol-based soft segment, which results in nanophase-separated thermoplastic polyurethane elastomers (TPUs), leads to single-phase PHUs that flow under the force of gravity. This PHU behavior is due to major phase mixing caused by hydrogen bonding of hard-segment hydroxyl groups to the soft-segment ether oxygen atoms. This hydrogen bonding can be suppressed by using polypropylene glycol-based or polytetramethylene oxide (PTMO)-based soft segments, which reduce hydrogen bonding by steric hindrance and dilution of oxygen atom content and result in nanophase-separated PHUs with robust, tunable mechanical properties. The PTMO-based PHUs exhibit reversible elastomeric response with hysteresis, like that of conventional TPUs. Because of nanophase separation with broad interphase regions possessing a wide range of local composition, the PTMO-based PHUs also demonstrate potential as novel broad-temperature-range acoustic and vibration damping materials, a function not observed with TPUs.

a b s t r a c tNon-isocyanate thermoplastic polyhydroxyurethane (PHU) elastomers were synthesized from cyclic carbonate aminolysis using polytetramethylene oxide (PTMO) as soft segment and divinylbenzene dicyclocarbonate and three diamine chain extenders as hard segment with a range of hard-segment content. Characterization was done via Fourier transform infrared spectroscopy, small-angle X-ray scattering (SAXS), uniaxial tensile testing, and dynamic mechanical analysis (DMA). SAXS reveals that these PHUs possess nanophaseseparated morphology with 10-20 nm interdomain spacings. These PHUs display elastomeric response and tunable tensile properties with Young's modulus ranging from 27 to 200 MPa, tensile strength from 0.3 to 9.7 MPa and elongation at break ranging up to greater than 2000%. DMA reveals that nanophase separation in these PHUs is accompanied by broad interphases having a wide range of local composition; this nanophase separation differs significantly from that manifested by thermoplastic polyurethane elastomer (TPU) due to hydrogen bonding of hydroxyl groups in the hard segments to the PTMO soft segment. These PHUs show very good damping performance with tan d P 0.30 over broad temperature ranges (P60°C), which are tunable through simple variation of hardsegment content and chain extender structures.

Non-isocyanate polyurethane (NIPU) was synthesized via cyclic carbonate aminolysis using poly(ethylene oxide) (PEO)-and poly(tetramethylene oxide) (PTMO)-based soft segments, divinylbenzene dicyclocarbonate as hard segment, and diamine−diamide (DDA) chain extender. Characterization of the resulting segmented polyhydroxyurethanes (PHUs) reveals that the use of amide-based DDA chain extender leads to unprecedented improvements in nanophase separation and thermal and mechanical properties over segmented PHUs without DDA chain extender. With PEO-based soft segments, previously known to yield only phase-mixed PHUs, use of DDA chain extender yields nanophaseseparated PHUs above a certain hard-segment content, as characterized by small-angle X-ray scattering. With PTMO-based soft segments, previously known to yield nanophase-separated PHUs with broad interphase, use of DDA chain extender produces nanophase-separated PHUs with sharp domain interphase, leading to wide, relatively temperature-independent rubbery plateau regions and much improved thermal properties with flow temperature as high as 200 °C. The PTMO-based PHUs with 19−34 wt % hard-segment content exhibit tunable mechanical properties with Young's modulus ranging from 6.6 to 43.2 MPa and tensile strength from 2.4 to 6.7 MPa, with ∼300% elongation at break. Cyclic tensile testing shows that these PHUs exhibit elastomeric recovery with attributes very similar to conventional, isocyanate-based thermoplastic polyurethane elastomers.

The 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.

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 δ ≥ 0.3 over temperature ranges exceeding 70 °C in breadth. In contrast, PBN-based PHUs have sharper interphases, evidenced by narrow tan δ peaks near soft-segment and hard-segment T g s as well as by DSC and AFM data. FTIR shows that the ratio of hydrogen-bonded carbonyl to free carbonyl