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John Torkelson

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Polyurethane (PU) and PU-like Materials with Reduced Reliance on Isocyanates

Thermoplastic polyurethane elastomers are commonly produced by reaction of isocyanate-terminated prepolymers with low molecular weight (MW) diols; the prepolymers are formed by reaction of a long-chain polyol with an excess of diisocyanate and, subsequently, chain extended with small molecule diol. The final material possesses nanophase-separated morphology with hard segments dispersed in a rubbery soft-segment matrix. The hard segments act as physical cross-links that promote elastomeric character. Global polyurethane (PU) production is expected to reach 18 million tons in 2016, with TPUs accounting for 5% of the global PU market.

Thermoplastic Polyhydroxyurethane Elastomers

Despite diverse and wide ranging applications of PUs, there has been increased regulatory scrutiny concerning the safe use and transport of isocyanates. Consequently, research into alternative pathways to PU or PU-like materials has intensified with aminolysis of five-membered-ring cyclic carbonates to produce polyhydroxyurethane (PHU) being one of the most promising chemistries.

E.K. Leitsch, G. Beniah, K. Liu, T. Lan, W.H. Heath, K.A. Scheidt, J.M. Torkelson, "Non-Isocyanate Thermoplastic Polyhydroxyurethane Elastomers via Cyclic Carbonate Aminolysis: Critical Role of Hydroxyl Groups in Controlling Nanophase Separation," ACS Macro Letters, 5, 424-429 (2016). [Link]

Thiol-Acrylate-Epoxide Hybrid Polymers

Polyurethane-like properties can also be achieved through different chemistries. We have demonstrated that click chemstries can produce phase-separated elastomers and shape memory materials without any using of isocyanates.

K. Jin, W.H. Heath, J.M. Torkelson, "Phase-Separated Thiol-Epoxy-Acrylate Hybrid Polymer Networks with Controlled Cross-link Density Synthesized by Simultaneous Thiol-Acrylate and Thiol-Epoxy Click Reactions," Macromolecules, 49, 4115-4123 (2016). [Link]

E.A. Dhulst, W.H. Heath, J.M. Torkelson, "Hybrid Thiol-Acrylate-Epoxy Polymer Networks: Comparison of One-Pot Synthesis with Sequential Reactions and Shape Memory Properties," Polymer, 96, 198-204 (2016). [Link]