Current trends in leather science

Abstract In preparing the second edition of ‘Tanning Chemistry. The Science of Leather.’, the literature was updated and the content was revised and reviewed. Here, the new findings are presented and discussed. Notable developments include the necessary rethinking of the mechanism of sulfide unhairing because of new understanding of the aqueous chemistry of sulfide species. Revision upwards of the value of the second pKa for sulfide species ionisation means that S2− cannot exist in an aqueous medium, so the unhairing species in hair burn reactions is HS−. Although the technology remains the same, this means the mechanisms of associated reactions such as immunisation must be revised. Rawstock preservation has benefitted from studies of the potential role of materials from plants which accumulate salt, but which also contribute terpene compounds. There is also further discussion on the continuing issue of chromium (VI) in the leather industry. The application to processing of new solvents, ionic liquids and deep eutectics, is the coming technology, which offers transforming options for new chemistries and products. Renewed interest in vegetable tanning and methods of wet white processing are current trends. Also, within the topic of reagent delivery is processing in a solid medium of plastic beads. Graphical abstrac

Choline-Based Amino Acid ILs–Collagen Interaction: Enunciating Its Role in Stabilization/Destabilization Phenomena

Given the potential of productive interaction between choline-based amino acid ionic liquids (CAAILs) and collagen, we investigated the role of four CAAILs, viz., choline serinate, threoninate, lysinate, and phenylalaninate, and the changes mediated by them in the structure of collagen at different hierarchical orderings, that is, at molecular and fibrillar levels. The rheological, dielectric behavior and the secondary structural changes signify the alteration in the triple helical structure of collagen at higher concentrations of CAAILs. A marginal swelling and slight decrease in the thermal stability of rat tail tendon collagen fibers were observed for choline serinate and threoninate, albeit distortions in banding patterns were noticed for choline lysinate and phenylalaninate, suggesting chaotropicity of the ions at the fibrillar level. This signifies the changes in the hydrogen-bonding environment of collagen with increasing concentrations of CAAILs, which could be due to competitive hydrogen bonding between the carbonyl group of amino acid ionic liquids and the hydroxyl groups of collagen

Electrostatic Forces Mediated by Choline Dihydrogen Phosphate Stabilize Collagen

Cross-linkers aid in improving biostability of collagen via different mechanisms. Choline dihydrogen phosphate (cDHP), a biocompatible ionic liquid, has been reported as a potential cross-linker for collagen. However, its mechanism is yet unclear. This study explores the effect of cDHP on the physicochemical stability of collagen and nature of its interaction. Dielectric behavior of collagen–cDHP composites signifies that cDHP enhances intermolecular forces. This was demonstrated by an increase in cross-linked groups and high denaturation temperature of collagen–cDHP composites. XRD measurements reveal minor conformational change in helices. Molecular modeling studies illustrate that the force existing between collagen and cDHP is electrostatic in nature. Herein, it is postulated that dihydrogen phosphate anion attaches to cationic functional groups of collagen, resulting in closer vicinity of various side chains of collagen, forming physical and chemical cross-links within collagen, contributing to its structural stability. Our study suggests that dihydrogen phosphate anions can be employed for developing a new class of biocompatible cross-linkers

SPEEK polymeric membranes for fuel cell application and their characterization: A review

209-219Design of polymeric membranes for fuel cells application requires suitable selection and modification of polymers. This review accounts the various polymeric membranes available for use in fuel cells, advantages of sulphonation of polymers, various sulphonation methods and the characterization techniques. Presently, SPEEK finds extensive application as polymeric membrane in fuel cells. The advantages of SPEEK include good mechanical properties, thermal stability, and toughness and some conductivity depending on degree of sulphonation

Role of Preferential Ions of Ammonium Ionic Liquid in Destabilization of Collagen

Ions play a key role in the destabilization of collagen. This study explores the effect of diethyl methyl ammonium methane sulfonate (AMS), an ionic liquid (IL), on different hierarchical orderings of collagen, namely, at the molecular and fibrillar levels. The rheological behavior and secondary structural changes reveal changes in the hydrogen-bonding environment of collagen, leading to alterations in the triple helical structure of collagen. An increase in the concentration of AMS resulted in swelling of rat-tail tendon fibers, and also, decreased thermal stability signifies that ions are obliged to destabilize collagen at the fibrillar level. Molecular modeling studies confirm that anions are judiciously held responsible for structural deformities in collagen, whereas cations have a tenuous effect. Thus, the preferential role of ions present in an ammonium IL has been elucidated in this study