Non-Isocyanate Polyurethane Thermoplastic Elastomer: Amide-Based Chain Extender Yields Enhanced Nanophase Separation and Properties in Polyhydroxyurethane

Abstract

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.

Degradation and stabilization of polyurethane elastomers

“…However, most of the non-isocyanate PU systems developed so far do not offer the advantages of rapid reaction at room temperature from liquid, low-viscosity precursors, industrial viability for both small-scale in-field applications and large-scale industrial applications without generating sideproducts, and the ability to form elastomeric materials that have a combination of appropriate elongation and tensile strength [99,103]. While a few non-isocyanate PU elastomers have been reported [94,96,98,99,109,111,113], these new materials have not been fully characterized yet,…”

Hydrophobilization of Furan-Containing Polyurethanes via Diels–Alder Reaction with Fatty Maleimides

“…Polyurethanes have a high variety of applications including coatings [1], foams [2,3], fibers [4,5,6], adhesives [7], and thermoplastic elastomers [5,8,9]. They are obtained from the reaction of isocyanates and alcohols.…”

Functionalization of hydroxyl groups in segmented polyhydroxyurethane eliminates nanophase separation

“…When a soft segment with no potential for intersegmental hydrogen bonding is used, such as polybutadiene‐based soft segment, nanophase‐separated PHUs with a much sharper domain interphase like that exhibited by conventional thermoplastic PU elastomer are obtained . Recently, Torkelson et al also reported that incorporating amide‐based, diamine diamide chain extender results in significant improvement in nanophase separation and properties of PHUs . If another method of eliminating intersegmental hydrogen bonding in PHUs is employed, in particular, via functionalization of the hard‐segment hydroxyl group, will well nanophase‐separated PHUs with sharp domain interphases result?…”

“…PHU is analogous to PU but possesses an additional hydroxyl group adjacent to every urethane linkage . Although there have been numerous studies on PHU synthesis in recent years, relatively few studies have been focused on segmented, nanophase‐separated PHUs . A significant fraction of conventional PU is segmented copolymer …”