Effect of Moisture on Polymer Deconstruction in HCl Gas Hydrolysis of Wood

Weakening the integrity of waxy starch granules by selective degradation of amorphous matrices using gaseous hydrogen chloride

Waxy corn starch with 6-12 % moisture was degraded by gaseous hydrogen chloride (HCl(g)) then characterized chromatographically and microscopically to investigate the relationship between moisture-resulting changes in unit chain properties of starch and its susceptibility to swelling. Starches with the highest degradation extents at different moisture content had recoveries of 76-83 % (w/w) and the weight-average degrees of polymerization of 66-93 anhydroglucose unit. Additionally, the HCl(g)-degraded starches were still of birefringent granules but with internal cavity. When increasing the swelling temperature from 25 to 40 °C, some granules showed enlarged internal cavity, and some were fragmented. Change in granule morphology, accompanied by leaching of constituting polymers, was particularly evident for starch with preferential degradation of B1 chains over B2+ chains as the moisture content decreased from 9 % to 6 %. These findings not only manifest the impact of changes in B2+ and B1 chains on the swelling characteristic of HCl(g)-degraded granules, but also demonstrate an approach for weakening the integrity of granules by selective degradation of amorphous matrices using HCl(g).

Wood-based superblack

Light is a powerful and sustainable resource, but it can be detrimental to the performance and longevity of optical devices. Materials with near-zero light reflectance, i.e. superblack materials, are sought to improve the performance of several light-centered technologies. Here we report a simple top-down strategy, guided by computational methods, to develop robust superblack materials following metal-free wood delignification and carbonization (1500 °C). Subwavelength severed cells evolve under shrinkage stresses, yielding vertically aligned carbon microfiber arrays with a thickness of ~100 µm and light reflectance as low as 0.36% and independent of the incidence angle. The formation of such structures is rationalized based on delignification method, lignin content, carbonization temperature and wood density. Moreover, our measurements indicate a laser beam reflectivity lower than commercial light stoppers in current use. Overall, the wood-based superblack material is introduced as a mechanically robust surrogate for microfabricated carbon nanotube arrays.