Freeze-dried ammonia borane-polyethylene oxide composites: Phase behaviour and hydrogen release

A solid-state hydrogen storage material comprising ammonia borane (AB) and polyethylene oxide (PEO) has been produced by freeze-drying from aqueous solutions from 0% to 100% AB by mass. The phase mixing behaviour of AB and PEO has been investigated using X-ray diffraction which shows that a new ‘intermediate’ crystalline phase exists, different from both AB and PEO, as observed in our previous work (Nathanson et al., 2015). It is suggested that hydrogen bonding interactions between the ethereal oxygen atom (–O–) in the PEO backbone and the protic hydrogen atoms attached to the nitrogen atom (N–H) of AB molecules promote the formation of a reaction intermediate, leading to lowered hydrogen release temperatures in the composites, compared to neat AB. PEO also acts to significantly reduce the foaming of AB during hydrogen release. A temperature-composition phase diagram has been produced for the AB-PEO system to show the relationship between phase mixing and hydrogen release

Crystalline structure of an ammonia borane-polyethylene oxide cocrystal: a material investigated for its hydrogen storage potential

The crystalline structure of a cocrystal comprising ammonia borane (AB) and a short-chain polyethylene oxide (PEO or PEG) has been determined by single-crystal X-ray diffraction. The components interact via hydrogen bonds between each of the hydrogen atoms at the NH3 end of the AB molecules and alternate oxygen atoms along the PEO backbone. The PEO chains in the structure exhibit an unusual conformation where their curvature reverses every 5 monomers, such that the polymer snakes through the crystal. This is the first time that an AB composite material has been determined to be a cocrystal, and no structure determination of a cocrystal to confine AB has been reported before

A novel ammonium pentaborate – poly(ethylene-glycol) templated polymer-inclusion compound

A new hydrogen-bonded supramolecular framework is reported, consisting of ammonium pentaborate, containing poly(ethylene-glycol) chains extending down tubular cavities in the structure. The crystal architecture is templated by the presence of the polyether chains, analogous to template synthesis of zeolites and metal organic frameworks. The ammonium pentaborate is formed by the thermolysis of ammonia borane, followed by hydrolysis of the dehydrogenation products by ambient water. This structure represents the first known example of a borate-based polymer inclusion compound

4D Printing of Magnetically Functionalized Chainmail for Exoskeletal Biomedical Applications

Chainmail fabrics manufactured by selective laser sintering 3D printing have been magnetically functionalized to create a lightweight, 4D printed, actuating fabric. The post-processing method involves submerging the porous prints in commercial ferrofluid (oil-based magnetic liquid), followed by drying under heat. The actuation of the chainmail has been simulated using a rigid multi-body physics engine, and qualitatively matches experiment. Such magnetically actuating fabrics have potential to make thin, lightweight and comfortable wearable assistive devices