Bio-composite hydrogels of cellulose and vulcanized natural rubber with nanointerconnected layers for reinforced water-retaining materials

Zn/Al layered double hydroxide and carboxymethyl cellulose composite beads as support for the catalytic gold nanoparticles and their applications in the reduction of nitroarenes

Until now, many efficient catalysts have been reported that are used for the reduction of nitroarenes. However, a catalyst reusability is a challenge that is often faced in practical environment. In this report, we designed a hydrogel composite (CMC-LDH), which act as support and making it possible to address this challenge. In this research work, zinc/aluminum based layered double hydroxides (Zn/Al LDH) have been assembled with carboxymethyl cellulose (CMC) to prepare CMC/LDH hydrogel beads. The CMC/LDH hydrogel beads were prepared by the ionotropic gelation method. For CMC/LDH/Au preparation, the already prepared CMC/LDH beads were kept in gold ion (Au3+) solution, and their subsequent reduction with sodium borohydride (NaBH4). For the characterization of the prepared samples different instrumental techniques, such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy, and scanning electron microscopy (SEM) were adopted. For the catalytic evaluation of CMC/LDH/Au, it was utilized as a catalyst in 4-NP and 4-NA reduction reactions. The continuity of the reaction was monitored by a UV-visible spectrophotometer. Rate constant (kapp) of 0.48474 min-1 and 0.7486 min-1 were obtained for 4-NP and 4-NA reduction, respectively. The hydrogel beads were recycled and reused for up to five successive cycles without significantly changing their catalytic efficiency.

Bromide and Chloride Ionic Liquids Applied to Enhance the Vulcanization and Performance of Natural Rubber Biocomposites Filled with Nanosized Silica

In this study, the possibility of using ionic liquids (ILs) as auxiliary substances improving the vulcanization and physicochemical properties of natural rubber (NR) biocomposites filled with nanosized silica was investigated. Hence, the influence of ILs with bromide and chloride anions and various cations, i.e., alkylimidazolium, alkylpyrrolidinium and alkylpiperidinium cation, on the curing characteristics and crosslink density of NR compounds was determined. Furthermore, the effect of nanosized silica and ILs on the functional properties of the obtained vulcanizates, including mechanical properties under static and dynamic conditions, hardness, thermal stability and resistance to thermo-oxidative aging, were explored. Applying nanosized silica improved the processing safety of NR compounds but significantly increased the optimal vulcanization time compared to the unfilled rubber. ILs significantly improved the cure characteristics of NR compounds by increasing the rate of vulcanization and the crosslink density of NR biocomposites. Consequently, the tensile strength and hardness of the vulcanizates significantly increased compared to that without ILs. Moreover, the use of nanosized silica and ILs had a favorable impact on the thermal stability of the vulcanizates and their resistance to prolonged thermo-oxidation.

Designing cellulose hydrogels from non-woody biomass

Hydrogels are an attractive system for a myriad of applications. While most hydrogels are usually formed from synthetic materials, lignocellulosic biomass appears as a sustainable alternative for hydrogel development. The valorization of biomass, especially the non-woody biomass to meet the growing demand of the substitution of synthetics and to leverage its benefits for cellulose hydrogel fabrication is attractive. This review aims to present an overview of advances in hydrogel development from non-woody biomass, especially using native cellulose. The review will cover the overall process from cellulose depolymerization, dissolution to crosslinking reaction and the related mechanisms where known. Hydrogel design is heavily affected by the cellulose solubility, crosslinking method and the related processing conditions apart from biomass type and cellulose purity. Hence, the important parameters for rational designs of hydrogels with desired properties, particularly porosity, transparency and swelling characteristics will be discussed. Current challenges and future perspectives will also be highlighted.