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Chitin and chitosan are the second most abundant natural biopolymers in the curst of the earth. These polysaccharide biopolymers have a long linear chain-like structure connected with β- d glucosidic linkage with the functionalizable surface groups. Because of the structural features, these biomaterials exhibit unique physical, chemical, mechanical and optical properties, which contributed to the tunable and outstanding properties such as low density, high porosity, renewability, natural biodegradability, and environmental friendliness, etc. Chitin was synthesized via mechanical, chemical, chemo-mechanical, and eco-friendly biological methods and the deacetylation of the synthesized chitin carried for the preparation of chitosan. With the chemical modification used for the preparation of chitosan, there occurs some minor change in characteristics; however, most of the properties were relatable due to major similarities in the microstructures. The inherent antibacterial, non-toxic, and biodegradable properties with the ease of processibility of both polymer has the potential to become a successful alternative to its synthetic counterparts for energy and environmental applications. However, the poor mechanical and thermal properties in comparison to the conventional alternatives have restricted its widespread applications. This review addresses various areas such as extraction techniques of chitin and synthesis of chitosan, discussion of the common characteristics of both polymers together such as crystallinity, thermal properties, mechanical properties, hydrophilicity, and surface charge. Moreover, this review paper also addresses the common functionalization techniques for both polymer and the use of both unmodified chitin and chitosan along with their derivatives in environmental and energy applications such as air pollution, heavy metal adsorption, dye adsorption, biosensors, EMI shielding, fuel cell, solar cell, lithium-ion batteries, and biofuels. Graphic Abstract

Industrial sea food residues, mainly crab and shrimp shells, are considered to be the most promising and abundant source of chitin. In-depth understanding of the biological properties of chitin and scientific advancements in the field of nanotechnology have enabled the development of high-performance chitin nanomaterials. Nanoscale chitin is of great economic value as an efficient functional and reinforcement material for a wide range of applications ranging from water purification to tissue engineering. The use of polymers and nanochitin to produce (bio) nanocomposites offers a good opportunity to prepare bioplastic materials with enhanced functional and structural properties. Most processes for nanochitin isolation rely on the use of chemical, physical or mechanical methods. Chitin-based nanocomposites are fabricated by various methods, involving electrospinning, freeze drying, etc. This review discusses the progress and new developments in the isolation and physico-chemical characterization of chitin; it also highlights the processing of nanochitin in various composite and functional materials.

The objective of this study was to assess the feasibility of using a poly(vinylidene fluoride) (PVDF) membrane modified with cellulose/nanostructures as a separation technique for the removal of poly(vinyl alcohol)(PVA)/reactive dyes from synthetic textile wastewater. The goal was to recycle PVA/reactive dye yellow 145 for reuse in the industry while simultaneously reclaiming water for reuse. To achieve this, the study aimed to evaluate the influence of SnO 2 /ZnO nanostructures on the polymer mixture, examining their impact on permeation and rejection of PVA/reactive dye. Additionally, the study investigated the antifouling properties of PVDF, both in the presence and absence of electrospun cellulose nanofibers. Chemical analysis techniques, including SEM, EDS, FTIR, mechanical strength testing, contact angle measurement, AFM, and determination of molecular weight cutoff (MWCO), were employed to assess the synthesized membranes. The MWCO results indicated a decrease in pore size after surface modification with electrospun cellulose acetate (CA), with the modified membrane (M2-Mod) showing a reduced MWCO of 6700 Da compared to the unmodified membrane’s MWCO of 13,980 Da. Furthermore, the study aimed to identify the optimal polymeric nanocomposite of PVDF with nano-SnO 2 or ZnO, along with electrospun cellulose nanofibers, to enhance %PVA and %dye rejection while improving membrane productivity and fouling resistance. The formulation containing a mixture of SnO 2 and ZnO, in the presence of electrospun CA, demonstrated superior performance, achieving 98% PVA rejection, 95% reactive dye rejection, and a stable flux of 20 LMH, with a normalized flux of 92%. Overall, it can be concluded that the optimized modified membrane formulation (M2-Mod) exhibited excellent antifouling behavior, holding significant potential for promoting circular economy and sustainability in textile wastewater treatment.

The application of biomass-derived renewable materials has generated great interest in recent research works. Among many such biopolymers, nanocellulose has become the leading topic in the sphere of sustainable material owing to the outstanding mechanical, chemical and thermal properties along with non-toxicity, surface functionality, ease of modification and sustainability. Nanocellulose is often considered to be a second-generation renewable resource and a better replacement for conventional petroleum-based products with or without any modifications. Even though some reviews have reported on some of the applications of nanocellulose, so far there is no comprehensive report gathering the extraction, properties, functionalization towards energy and environmental applications. This review aims to present the use of nanocellulose based materials for energy and environmental challenges. Important characteristics such as crystallinity, hydrophilicity, thermal decomposition and surface charge are described as a function of the targeted applications. In the latter part of this review, we have looked into the recent studies in the area of applications such as air pollution, heavy metal sorption, dye adsorption, biosensors, EMI shielding, fuel cell, solar cell, lithium-ion batteries and biofuels etc. However, a green, sustainable and scalable nanocellulose extraction is yet to be fulfilled. In our view, the bacterial nanocellulose based approach can address all these issues with the added advantage of producing a very high purity of nanocellulose. Hence this review is intended to provide new insights into the field of eco-friendly functional materials with included in-depth perspectives about nanocellulose and its future based on the current research trends.

Considerable interest in food packaging research has been prompted by the rising environmental impact of waste, customer awareness for readily accessible foods with extended shelf life, and ecological consciousness about the scarcity of natural resources. The utilization of plastic-based food packaging has resulted in a significant environmental concern due to the accumulation of substantial quantities of plastic in the surrounding areas. Research efforts are being motivated by ecological and health considerations in the pursuit of developing biodegradable films. Besides, poly(lactic acid) (PLA) has been suggested as a possible substitute for petroleum-based polymers because of its sustainability, simple accessibility, and biodegradability. PLA is a biodegradable plastic made from sugar beet or maize starch that may be fermented by bacteria to generate material with desirable qualities like transparency and rigidity. However, there is a need for further improvement in certain properties of PLA, such as flexibility, toughness, permeability, and thermal properties. One potential approach for enhancing these attributes involves the integration of nano-reinforcement. The utilisation of nanocellulose derived from biomass has garnered significant interest in recent times owing to its renewable nature, ability to biodegrade, impressive mechanical strength, low density, and considerable economic worth. In this study, we present a comprehensive overview of the most up-to-date methods for synthesising nanocellulose and its use as a filler material in the manufacture of PLA nanocomposites for food packaging. In addition, this study examines the emerging challenges and potential advantages associated with the utilization of PLA biocomposites incorporated with nanocellulose in the food packaging sector.

Recent studies have demonstrated the efficacy of graphene oxide (GO) as an adsorbent for removing various dyes from water, owing to its large surface area, high porosity, and abundance of oxygen-containing functional groups. The primary goal of this review article is to collect the dispersed information of a diverse range of efficient GO composite adsorbents to remove dyes from water, providing a comprehensive overview of their synthesis, characterization, and functionalization methods. Various modification approaches of GO that increase its adsorption capacity are discussed in detail, as well as influencing factors on its performance, which include adsorbent dosage, initial dye concentration, nature of functional groups, contact time, pH, and temperature. Additionally, this review explores the adsorption mechanisms of dyes onto various GO-based materials and the extent to which different adsorption kinetics and isotherm models are applied. Such models include Langmuir and Freundlich that can further improve the understanding of dye–adsorbent interactions and help to design more efficient adsorption systems. It also covers a summary of the dye adsorption capacities of different GO composites and the parameters that control performance. On the basis of the extensive literature studied, critical insights were drawn, and several recommendations for future research were proposed, including the exploration of more sustainable synthesis routes and the development of novel functionalized GO composites. Graphical abstract

Polymer nanocomposites have been attracting significant interest over the last three decades. One of the most intriguing applications is related to the preparation of clay-filled nanocomposites based on rubber blend matrices. Although several studies already exist on the subject, there is limited information available regarding their rheological, thermal, and, particularly, damping behaviour of rubber blend systems. In this work, the rheological, viscoelastic, and thermal behaviour of a natural rubber/nitrile rubber (NR/NBR) blend nanocomposite containing organically modified nanoclay was systematically investigated, and the damping characteristics were also assessed. At a lower nanoclay concentration (5 phr), network formation through filler–filler and filler–polymer interactions led to partial immobilization of polymer chains, resulting in a pronounced increase in viscosity and enhanced viscoelastic response. In contrast, at higher nanoclay loading (10 phr), strong agglomeration of filler particles occurred, corresponding to a stacked clay morphology, which hindered effective filler–filler network formation and weakened filler–polymer interactions, leading to lower viscosity and reduced damping efficiency. The blend composition and filler content were found to significantly influence the investigated properties, especially the hysteresis loss and the thermal conductivity, which is explained by matrix–filler interactions and the resulting morphology of the system.

In this study, tests were conducted to examine the morphological, mechanical, and wetting properties of thermoplastic composites using banana fiber (BF) an agro-residue as a filler. Plasma-treated polyethylene (PPE) was used as the matrix, and compression molding technique was used for composite preparation. Treated and untreated polyethylene (UPE) banana fiber composites were compared in terms of the interfacial adhesion between the fiber and the matrix. Fibers were added in varying amount (10, 20, 30, and 40 by weight %) into the polymer to investigate the fiber-matrix interaction in each case and also to optimize the composition that would yield improved properties. Morphological properties were studied using scanning electron microscopic (SEM) studies, surface wettability was studied using the contact angle method and FTIR analysis was used to confirm the effectiveness of the functionalization. SEM analysis showed that PPE-BF composites have better interfacial adhesion between the polymer and fiber as compared to UPE-BF composites. Also, PPE-BF showed a maximum of 6% and 25% increment in tensile strength and Young’s modulus. Wettability studies showed that contact angle values got decreased from 93° (UPE-BF20) to 77° (PPE-BF20), which proves the effectiveness of plasma treatment through incorporation of new functionalization (polar groups) on the surface of the polymer in treated composites, and also which shows how the treatment enhanced the interfacial bonding between polymer and fiber.

In this paper, the calorimetric response of the amorphous phase was examined in hybrid nanocomposites which were prepared thanks to a facile synthetic route, by adding reduced graphene oxide (rGO), Cloisite 30B (C30B), or multiwalled carbon nanotubes (MWCNT) to lignin-filled poly(lactic acid) (PLA). The dispersion of both lignin and nanofillers was successful, according to a field-emission scanning-electron microscopy (FESEM) analysis. Lignin alone essentially acted as a crystallization retardant for PLA, and the nanocomposites shared this feature, except when MWCNT was used as nanofiller. All systems exhibiting a curtailed crystallization also showed better thermal stability than neat PLA, as assessed from thermogravimetric measurements. As a consequence of favorable interactions between the PLA matrix, lignin, and the nanofillers, homogeneous dispersion or exfoliation was assumed in amorphous samples from the increase of the cooperative rearranging region (CRR) size, being even more remarkable when increasing the lignin content. The amorphous nanocomposites showed a signature of successful filler inclusion, since no rigid amorphous fraction (RAF) was reported at the filler/matrix interface. Finally, the nanocomposites were crystallized up to their maximum extent from the glassy state in nonisothermal conditions. Despite similar degrees of crystallinity and RAF, significant variations in the CRR size were observed among samples, revealing different levels of mobility constraining in the amorphous phase, probably linked to a filler-dimension dependence of space filling.

The paper reports the study of surface roughness based opto-mechanical properties of Chlorobutyl (CIIR)/Natural Rubber (NR) 70/30 polymers filled with different contents of hybrid (CB/CN) using indigenously designed THz spectrophotometer between 1 and 2.0 THz range. The carbon black (CB) and Carbon nano powders were mixed between 20 and 2.0–7.5 Phr range in the chlorobutyl and natural rubber matrix for improvising their surface quality and mechanical strength. The physical and structural changes were ascertained in terms of transmission, refractive indices and absorption coefficients. The percentage of filler also influences the morphology and surface roughness quality of the rubber due to intercalation and measured in terms of surface roughness factor ‘g’ optical impedance ‘z’ and reflection coefficients between 0.1 and 2.0 THz range. The obtained values of optical impedance lie between 220.2 and 235.6 Ω range and were correlated with the mechanical strength of the rubber samples. It provides a new modality to understand the effect of fillers on the strength of rubber samples.