Chemical treatment of end-of-life PVC at high temperature often results in the formation of polyacetylene and eventually aromatic char. These insoluble conjugated polymers lead to industrial reactor blockages, and limit the efficiency in recycling chlorinated plastic waste. To address this challenge, a solvent-based tandem dehydrochlorination–hydrogenation process is proposed for the conversion of PVC to a saturated polymer backbone. When combining tetrabutylphosphonium ionic liquids and homogeneous Rh catalysts under H₂ pressure, 81% dehydrochlorination is reached in 2 h, with the hydrogenation proceeding smoothly with minimal catalyst use of 0.5–2.0 mol% Rh. This process for PVC dechlorination yields soluble products that lack aromatics, have high degrees of dechlorination and possess a tunable content of double bonds. The chemical structures of the partially unsaturated polymer products and of the different structural motifs in the product are accurately monitored by a liquid ¹H-NMR method. Finally, X-ray absorption spectroscopy (XAS) sheds light on the catalytic Rh species during the tandem process, which are stabilized by the ionic liquid. This tandem process enables rapid PVC conversion to a saturated organic product, with polyethylene segments giving the opportunity for ensuing recycling steps.

Polyurethane ranks as one of the most significant plastics globally in terms of production volume and economic value, serving a crucial role in modern society. Due to complexities in the chemical recycling of polyurethane, replacement rates in recycled materials tend to be low, and the recovery of the isocyanate-derived aromatic compounds is often neglected. While many recycling efforts try to address these shortcomings, they primarily focus on TDI-based flexible foams, as recycling rigid PU foams is more challenging. In this work, ammonolysis is reported as an effective method for the recycling of rigid PU foams using ammonia to efficiently produce aromatic amines and polyols, while enabling easy recovery of the excess ammonia. A quantitative ¹H NMR analysis method was developed for rigid PU materials, allowing for the identification and quantification of the polyol and isocyanate-derived products of rigid PU. For ammonolysis, volumetric productivities of up to 300 g·L^–1·h^–1 were obtained, surpassing current rigid PU recycling processes and highlighting its industrial significance. Kinetic studies provided mechanistic insight into PU depolymerization, with urea linkages splitting fastest, followed by carbamates and finally isocyanurates. Furthermore, solid-state NMR analysis demonstrated ammonia’s hydrogen bonds disrupting effect in PU hard segments, presenting ammonolysis as an optimal method for recycling rigid PU foams, where the high content of hard segments makes degradation more challenging. The ammonolysis mixture could be purified into pure polyol and aromatic amine product fractions using two different separation methods. Finally, to highlight its industrial potential, our ammonolysis approach was demonstrated on various PU materials, extending the scope to end-of-life rigid PU waste materials. A comprehensive recycling process was applied, surpassing current rigid PU recycling efforts by reaching high isolated yields for isocyanate derivatives and polyol.

The three‐dimensional structure of canecystatin‐1, a potent inhibitor of cysteine proteases from sugarcane (Saccharum officinarum), has been solved in two different crystal forms. In both cases, it is seen to exist as a domain‐swapped dimer, the first such observation for a cystatin of plant origin. Size exclusion chromatography and multidimensional NMR spectroscopy show the dimer to be the dominant species in solution, despite the presence of a measurable quantity of monomer undergoing slow exchange. The latter is believed to be the active species, whereas the domain‐swapped dimer is presumably inactive, as its first inhibitory loop has been extended to form part of a long β‐strand that forms a double‐helical coiled coil with its partner from the other monomer. A similar structure is observed in human cystatin C, but the spatial disposition of the two lobes of the dimer is rather different. Dimerization is presumably a mechanism by which canecystatin‐1 can be kept inactive within the plant, avoiding the inhibition of endogenous proteases. The structure described here provides a platform for the rational design of specific cysteine protease inhibitors for biotechnological applications.Database: The coordinates and structure factors have been deposited in the Protein Data Bank under the accession codes 3UL5 and 3UL6.Structured digital Canecystatin-1 and Canecystatin-1 bind by molecular sieving (View Interaction: 1, 2) Canecystatin-1 and Canecystatin-1 bind by nuclear magnetic resonance (View interaction) Canecystatin-1 and Canecystatin-1 bind by dynamic light scattering (View interaction) Canecystatin-1 and Canecystatin-1 bind by x-ray crystallography (View interaction)

Enzymatic hydrolysis is a crucial step of biomass conversion into biofuels and different pretreatments have been proposed to improve the process efficiency. Amongst the various factors affecting hydrolysis yields of biomass samples, porosity and water accessibility stand out due to their intimate relation with enzymes accessibility to the cellulose and hemicellulose fractions of the biomass. In this work, sugarcane bagasse was subjected to acid and alkali pretreatments. The changes in the total surface area, hydrophilicity, porosity and water accessibility of cellulose were investigated by scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). Changes in chemical and physical properties of the samples, caused by the partial removal of hemicellulose and lignin, led to the increase in porosity of the cell walls and unwinding of the cellulose bundles, as observed by SEM. 1H NMR relaxation data revealed the existence of water molecules occupying the cores of wide and narrow vessels as well as the cell wall internal structure. Upon drying, the water molecules associated with the structure of the cell wall did not undergo significant dynamical and partial moisture changes, while those located in the cores of wide and narrow vessels kept continuously evaporating until reaching approximately 20% of relative humidity. This indicates that water is first removed from the cores of lumens and, in the dry sample, the only remaining water molecules are those bound to the cell walls. The stronger interaction of water with pretreated bagasse is consistent with better enzymes accessibility to cellulose and higher efficiency of the enzymatic hydrolysis. We were able to identify that sugarcane bagasse modification under acid and basic pretreatments change the water accessibility to different sites of the sample, associated with both bagasse structure (lumens and cell walls) and hydrophilicity (lignin removal). Furthermore, we show that the substrates with increased water accessibility correspond to those with higher hydrolysis yields and that there is a correlation between experimentally NMR-measured transverse relaxation times and the efficiency of enzymatic hydrolysis. This might allow for semiquantitative estimates of the enzymatic hydrolysis efficiency of biomass samples using inexpensive and non-destructive low-field 1H NMR relaxometry methods.