Glass transition temperature (Tg) plays an important role in controlling the mechanical and thermal properties of a polymer. Polyimides are an important category of polymers with wide applications because of their superior heat resistance and mechanical strength. The capability of predicting Tg for a polyimide a priori is therefore highly desirable in order to expedite the design and discovery of new polyimide polymers with targeted properties and applications. Here we explore three different approaches to either compute Tg for a polyimide via all-atom molecular dynamics (MD) simulations or predict Tg via a mathematical model generated by using machine-learning algorithms to analyze existing data collected from literature. Our simulations reveal that Tg can be determined from examining the diffusion coefficient of simple gas molecules in a polyimide as a function of temperature and the results are comparable to those derived from data on polymer density versus temperature and actually closer to the available experimental data. Furthermore, the predictive model of Tg derived with machine-learning algorithms can be used to estimate Tg successfully within an uncertainty of about 20 degrees, even for polyimides yet to be synthesized experimentally.

Polyurea elastomers derived in part from a bio-sourced feedstock and synthesized using an isocyanate-, solvent-, and catalyst-free approach exhibit elastomeric properties while maintaining melt-processibility.

1,1′‐Carbonyldiimidazole (CDI) provides a platform to generate high molecular weight polyurethanes from industrially relevant diols and diamines. CDI, which is described in the literature for its use in amidation and functionalization reactions, enables the production of well‐defined and stable polyurethane precursors, thus eliminating the need for isocyanates. Herein, the functionalization of 1,4‐butanediol with CDI yields an electrophilic biscarbamate, bis‐carbonylimidazolide (BCI), which is suitable for further step‐growth polymerization in the presence of amines. Elevated reaction temperatures enable the solvent‐, catalyst‐, and isocyanate‐free polycondensation reaction between the BCI monomer and various diamines. The thermoplastic polyurethanes produced from this reaction demonstrate high thermal stability, tunable glass transition temperatures based on incorporation of flexible polyether segments, and mechanically ductile thin films. CDI functionalized diols will allow the preparation of diverse polyurethanes without the use of isocyanate‐containing monomers.

Polyurethane foams remain at the forefront of cushioning, insulation, packaging, and structural applications. Risk of exposure to isocyanate-containing precursors during foaming operations directly contributes to the regulation of isocyanates, thus...