Engineering chitosan into fully bio-sourced, water-soluble and enhanced antibacterial poly(aprotic/protic ionic liquid)s packaging membrane

The design and facile preparation of water-soluble and eco-friendly polymer packaging membrane materials is a fascinating research topic, particularly in terms of the increasing concerns on potential microplastics pollution in ecosystem. In this study, taking advantages of the structural features of chitosan (CS) and betaine hydrochloride (BHC), fully bio-sourced and water-soluble poly(aprotic/protic ionic liquid)s (PAPILs) were successfully designed and prepared through the reaction of the amino groups in CS and carboxyl groups in BHC. The structure and thermo-properties of the PAPILs were elucidated by a series of characteristic methods. The rheological properties of the PAPILs aqueous solutions were also investigated. Moreover, water-soluble PAPILs membrane with a smooth surface morphology and a tensile strength of 62.9 MPa was successfully prepared. The PAPILs membrane also exhibited satisfactory biocompatibility, excellent antibacterial activities and high oxygen barrier property. Together with these outstanding material performance and functionality, as a "proof of concept", the potential use of the PAPILs membrane as water-soluble packaging material for laundry detergent capsule and pesticide was preliminarily demonstrated. These findings provide significant insights for the design of sustainable and functional packaging materials by using natural resources.

Thermal Stability for the Continuous Production of γ-Valerolactone from the Hydrogenation of N-Butyl Levulinate in a CSTR

γ-valerolactone can be a game-changer in the chemical industry because it could substitute fossil feedstocks in different fields. Its production is from the hydrogenation of levulinic acid or alkyl levulinates and can present some risk of thermal runaway. To the best of our knowledge, no studies evaluate the thermal stability of this production in a continuous reactor. We simulated the thermal behavior of the hydrogenation of butyl levulinate over Ru/C in a continuous stirred-tank reactor and performed a sensitivity analysis. The kinetic and thermodynamic constants from Wang et al.’s articles were used. We found that the risk of thermal stability is low for this chemical system.

Viscoelasticity of Low-Molecular-Weight Polyelectrolytes

Shear-thickening fluids that absorb the impact energy of high-velocity projectiles are of great interest for aerospace and body-armor applications. In such a frame, we investigate transient states of neat and aqueous polyelectrolytes (PE) having low molecular weights and containing poly([2-(methacryloyloxy)ethyl]trimethylammonium) as polycations and poly(acrylamide-co-acrylic acid) as polyanions. We compare results with those of bulk water. We employ nonequilibrium molecular dynamics to simulate oscillatory shear, mainly in the linear viscoelastic regime. We find that neat PE exhibits properties of a viscoelastic solid, whereas water and the aqueous mixture of PE conform to viscoelastic liquids with Maxwellian behavior at low angular frequencies. Terminal relaxation times are ∼0.499 and ∼1.385 ps for water and the aqueous mixture of PE, respectively. At high angular frequencies, storage moduli show anomalous behaviors that correspond to transitions between shear thinning and shear thickening in complex shear viscosities. The change in potential energy with the increase of the angular frequency is mainly driven by intramolecular interactions for neat PE, whereas short-range Coulomb interactions are the major contributions for water and the aqueous mixture of PE. Upon observation of the molecular configurations, only the local polyionic structure in the aqueous mixture of PE shows improvement when increasing the angular frequency, whereas the rest remains barely affected. Thus, the water structure in the aqueous mixture of PE allows the storage of energy elastically through the hydrogen-bond network at large angular frequencies, whereas the mechanical contribution of polyions weakens and fully vanishes at the beginning of shear thinning, explaining the superimposed data with data of bulk water. Our method and findings set the path for future molecular simulations in the nonlinear viscoelastic regime with more complex underlying molecular mechanisms.

Progress on chemical modification of cellulose in “green” solvents

Chemical modification of cellulose in "green" solvents.

Use of Ionic Liquids and Deep Eutectic Solvents in Polysaccharides Dissolution and Extraction Processes towards Sustainable Biomass Valorization

A shift to a bioeconomy development model has been evolving, conducting the scientific community to investigate new ways of producing chemicals, materials and fuels from renewable resources, i.e., biomass. Specifically, technologies that provide high performance and maximal use of biomass feedstocks into commodities with reduced environmental impact have been highly pursued. A key example comprises the extraction and/or dissolution of polysaccharides, one of the most abundant fractions of biomass, which still need to be improved regarding these processes' efficiency and selectivity parameters. In this context, the use of alternative solvents and the application of less energy-intensive processes in the extraction of polysaccharides might play an important role to reach higher efficiency and sustainability in biomass valorization. This review debates the latest achievements in sustainable processes for the extraction of polysaccharides from a myriad of biomass resources, including lignocellulosic materials and food residues. Particularly, the ability of ionic liquids (ILs) and deep eutectic solvents (DESs) to dissolve and extract the most abundant polysaccharides from natural sources, namely cellulose, chitin, starch, hemicelluloses and pectins, is scrutinized and the efficiencies between solvents are compared. The interaction mechanisms between solvent and polysaccharide are described, paving the way for the design of selective extraction processes. A detailed discussion of the work developed for each polysaccharide as well as the innovation degree and the development stage of dissolution and extraction technologies is presented. Their advantages and disadvantages are also identified, and possible synergies by integrating microwave- and ultrasound-assisted extraction (MAE and UAE) or a combination of both (UMAE) are briefly described. Overall, this review provides key information towards the design of more efficient, selective and sustainable extraction and dissolution processes of polysaccharides from biomass.