3D Printable Non-Isocyanate Polyurethanes with Tunable Material Properties.

Green chemistry-based non-isocyanate polyurethanes (NIPU) are synthesized and 3D-printed via rapid, projection photopolymerization into compliant mechanisms of 3D structure with spatially-localized material properties. Trimethylolpropane allyl ether-cyclic carbonate is used to couple the unique properties of two types of reaction chemistry: (1) primary diamine-cyclic carbonate ring-opening conjugation for supplanting conventional isocyanate-polyol reactions in creating urethane groups, with the additional advantage of enabling modular segment interchangeability within the diurethane prepolymers; and (2) thiol-ene (click) conjugation for non-telechelic, low monodispersity, quasi-crystalline-capable, and alternating step-growth co-photopolymerization. Fourier Transform Infrared Spectroscopy is used to monitor the functional group transformation in reactions, and to confirm these process-associated molecular products.

High-Entropy Metal Diborides: A New Class of High-Entropy Materials and a New Type of Ultrahigh Temperature Ceramics.

Seven equimolar, five-component, metal diborides were fabricated via high-energy ball milling and spark plasma sintering. Six of them, including (HfZrTaNbTi)B, (HfZrTaMoTi)B, (HfZrMoNbTi)B, (HfMoTaNbTi)B, (MoZrTaNbTi)B, and (HfZrTaCrTi)B, possess virtually one solid-solution boride phase of the hexagonal AlB structure. Revised Hume-Rothery size-difference factors are used to rationalize the formation of high-entropy solid solutions in these metal diborides.