A Carbodiimide-Fueled Reaction Cycle That Forms Transient 5(4H)-Oxazolones.

In life, molecular architectures, like the cytoskeletal proteins or the nucleolus, catalyze the conversion of chemical fuels to perform their functions. For example, tubulin catalyzes the hydrolysis of GTP to form a dynamic cytoskeletal network. In contrast, myosin uses the energy obtained by catalyzing the hydrolysis of ATP to exert forces. Artificial examples of such beautiful architectures are scarce partly because synthetic chemically fueled reaction cycles are relatively rare. Here, we introduce a new chemical reaction cycle driven by the hydration of a carbodiimide. Unlike other carbodiimide-fueled reaction cycles, the proposed cycle forms a transient 5(4H)-oxazolone. The reaction cycle is efficient in forming the transient product and is robust to operate under a wide range of fuel inputs, pH, and temperatures. The versatility of the precursors is vast, and we demonstrate several molecular designs that yield chemically fueled droplets, fibers, and crystals. We anticipate that the reaction cycle can offer a range of other assemblies and, due to its versatility, can also be incorporated into molecular motors and machines.

Fiber Spinning of Ultrahigh Molecular Weight Isotactic Polypropylene: Melt Spinning and Melt Drawing.

Herein, this work reports fiber spinning of tailored isotactic polypropylene (iPP) by melt spinning and melt drawing, yielding an adjustable diameter of 40-400 µm. The crystallinity of all obtained fibers with a molecular weight between 330-1400 kg/mol is increased by thermal annealing and investigated via differential scanning calorimetry (DSC) as well as wide angle X-ray scattering (WAXS). The potential of ultrahigh molecular weight iPP (UHMW-iPP) fibers compared to fibers manufactured from industrially available iPP becomes evident when the mechanical performance is compared: fibers spun from UHMW-iPP (1400 kg/mol) enable a tensile strength of up to 400 MPa, whereas commercially available fibers (330 kg/mol) show a tensile strength of approximately 50 MPa. However, UHMW-iPP exhibits a short timeframe, in which extrusion is possible, thereafter extrusion rupture occurs, probably induced by an increased melt viscosity.