Susheel Kalia

Cellulose-Based Bio- and Nanocomposites: A Review

Cellulose macro- and nanofibers have gained increasing attention due to the high strength and stiffness, biodegradability and renewability, and their production and application in development of composites. Application of cellulose nanofibers for the development of composites is a relatively new research area. Cellulose macro- and nanofibers can be used as reinforcement in composite materials because of enhanced mechanical, thermal, and biodegradation properties of composites. Cellulose fibers are hydrophilic in nature, so it becomes necessary to increase their surface roughness for the development of composites with enhanced properties. In the present paper, we have reviewed the surface modification of cellulose fibers by various methods. Processing methods, properties, and various applications of nanocellulose and cellulosic composites are also discussed in this paper.

Nanofibrillated cellulose: surface modification and potential applications

Interest in nanofibrillated cellulose has been increasing exponentially because of its relatively ease of preparation in high yield, high specific surface area, high strength and stiffness, low weight and biodegradability etc. This bio-based nanomaterial has been used mainly in nanocomposites due to its outstanding reinforcing potential. Solvent casting, melt mixing, in situ polymerization and electrospinning are important techniques for the fabrication of nanofibrillated cellulose-based nanocomposites. Due to hydrophilic character along with inherent tendency to form strong network held through hydrogen-bonding, nanofibrillated cellulose cannot uniformly be dispersed in most non-polar polymer matrices. Therefore, surface modification based on polymer grafting, coupling agents, acetylation and cationic modification was used in order to improve compatibility and homogeneous dispersion within polymer matrices. Nanofibrillated cellulose opens the way towards intense and promising research with expanding area of potential applications, including nanocomposite materials, paper and paperboard additive, biomedical applications and as adsorbent.

Magnetic polymer nanocomposites for environmental and biomedical applications

Hybrid nanomaterials have received voluminous interest due to the combination of unique properties of organic and inorganic component in one material. In this class, magnetic polymer nanocomposites are of particular interest because of the combination of excellent magnetic properties, stability, and good biocompatibility. Organic–inorganic magnetic nanocomposites can be prepared by in situ, ex situ, microwave reflux, co-precipitation, melt blending, and ceramic–glass processing and plasma polymerization techniques. These nanocomposites have been exploited for in vivo imaging, as superparamagnetic or negative contrast agents, drug carriers, heavy metal adsorbents, and magnetically recoverable photocatalysts for degradation of organic pollutants. This review article is mainly focused on fabrication of magnetic polymer nanocomposites and their applications. Different types of magnetic nanoparticles, methods of their synthesis, properties, and applications have also been reviewed briefly. The review also provides detailed insight into various types of magnetic nanocomposites and their synthesis. Diverse applications of magnetic nanocomposites including environmental and biomedical uses have been discussed.

Fabrication and characterization of chitosan-crosslinked-poly(alginic acid) nanohydrogel for adsorptive removal of Cr(VI) metal ion from aqueous medium.

In this study, chitosan-crosslinked-poly (alginic acid) nanohydrogel (CN-cl-PL(AA)NHG) was synthesized by co-polymerization method. It was used an effective adsorbent for the exclusion of Cr(VI) metal ion from aqueous medium. The synthesized nanohydrogel was characterized by FTIR, SEM and TEM. The TEM images clearly indicated the appearance of smooth surface with average size of particles ranging from 30 to 80nm. The effect of different adsorption parameters like agitation time, temperature, initial metal ion concentration and adsorbent dosage was studied and optimized. The results demonstrated that the prepared chitosan-crosslinked-poly (alginic acid) nanohydrogel had high adsorption tendency for the removal of Cr(VI) from the aqueous solution. The pseudo-second-order equation represented the better adsorption kinetics for the adsorption process. The thermodynamic studies showed the adsorption of Cr(VI) onto CN-cl-PL(AA)NHG was spontaneous and chemical in nature.

Magnetically recoverable ZrO2/Fe3O4/chitosan nanomaterials for enhanced sunlight driven photoreduction of carcinogenic Cr(VI) and dechlorination & mineralization of 4-chlorophenol from simulated waste water

In this laboratory-scale experiment we report the treatment of carcinogenic Cr(VI) and 4-chlorophenol by ferromagnetic ZrO2/Fe3O4 nano-heterojunctions supported on chitosan. A combination of different semiconductors with different photo-activities has proven to be a tested and effective technique for harnessing solar light in waste water treatment. The prepared heterojunction and its composite with chitosan has been characterized by X-Ray Diffraction (XRD), Fourier Transform Infra Red spectroscopy (FTIR), High Resolution Transmission Electron Microscopy (HRTEM), Small Area Electron Diffraction (SAED), Vibrating Sample Magnetometry (VSM), Energy Dispersive X-ray analysis (EDX), UV-visible spectrophotometry and Brunauer–Emmet–Teller surface area analysis (BET). Treatment of chlorophenols is challenging because of their hydrophobicity and stability. In our study we have reported excellent results for the dechlorination of 4-chlorophenol and the results were analyzed in terms of Liquid Chromatography-Mass Spectrometry (LC-MS), Chemical Oxygen Demand analysis (COD) and emission. 88.6% of 4-CP degradation was achieved in the presence of ZrO2/Fe3O4/chitosan in 3 h under sunlight and a reduction of 90.2% for Cr(VI) was obtained. The heterojunction formation leads to charge separation and decreased recombination of charge carriers. The synergistic effects of charge separation in the heterojunction, alcohols, peroxide, magnetism and adsorption with essential explanation of mechanisms make this study important and promising.

Synthesis and Characterization of Graft Co-Polymers of Flax Fiber with Binary Vinyl Monomers

Abstract Grafting of flax fiber with binary vinyl monomer mixtures such as methylmethacrylate (MMA)/ethyl acrylate (EA), MMA/acrylonitrile (AN), and MMA/acrylic acid (AA) was carried out. At a pressure of 8 Kg/cm2 under optimum reaction conditions 41.74% grafting resulted. Maximum grafting (109.9%) was found with MMA + EA binary monomer mixture. Synthesized graft co-polymers were characterized with FT-IR spectroscopy, scanning electron microscopy (SEM), TGA/DTA techniques, and X-ray diffraction (XRD). Thermal stability of flax-g-poly(MMA/AA) was found to more than that of flax fiber and other graft co-polymers. On grafting, percentage crystallinity decreases rapidly with reduction in its stiffness and hardness. Flax fiber showed the highest value of percentage crystallinity (76.96 %) and crystallinity index (0.7005) in comparison to flax-g-co-polymers.

Mercerization of Flax Fiber Improves the Mechanical Properties of Fiber-Reinforced Composites

In this article, modification of mercerized flax (MFx) through graft co-polymerization with methylmethacrylate (MMA) using ferrous ammonium sulphate–potassium per sulphate (FAS–KPS) redox initiator has been reported. Water uptake and moisture absorbance properties of methylmethacrylate grafted mercerized flax (MFx-g-MMA) and mechanical behavior of raw flax, mercerized flax, and MFx-g-MMA fibers reinforced—polystyrene matrix–based composites also have been evaluated. Four reaction parameters, reaction temperature, reaction time, initiator molar ratio, and monomer concentration, have been optimized to get maximum graft yield. Maximum graft yield of 138.35% has been obtained at optimum reaction conditions. The graft co-polymers thus formed were characterized by FTIR, TGA, and SEM techniques. Mercerized flax fiber reinforced showed better results than raw flax and MFx-g-MMA fibers reinforced composites.

Biodegradable and conducting hydrogels based on Guar gum polysaccharide for antibacterial and dye removal applications

Conducting hydrogels possessing antibacterial activity were developed using a two-step free-radical aqueous polymerization method to incorporate polyaniline chains into an adsorbent Guar gum/acrylic acid hydrogel network. The material properties of the synthesized samples were characterized using FTIR spectroscopy, thermal analysis and scanning electron microscopy techniques. Conducting hydrogels were tested for antibacterial activities against gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacteria and demonstrated antibacterial activity. Synthesized hydrogel samples can be potential adsorbent materials for dye removal applications.

Polysaccharide based graft copolymers

From the contents: Polymer Grafting: A Versatile Means to Modify the Polysaccharides.- Cellulose graft copolymers: Synthesis, Properties and Applications.- Starch-g-copolymers: Synthesis, Properties and Applications.- Chitosan-g-copolymers: Synthesis, Properties and Applications.- Gum-g-copolymers: Synthesis, Properties and Applications.- Dextran-g-copolymers: Synthesis, Properties and Applications.- Polysaccharide hydrogels: synthesis, characterization and applications.- Hyaluronic acid-g-copolymers: Synthesis, Properties and Applications.- Polysaccharide based graft copolymers for biomedical applications.

Synthesis and properties of poly(acrylamide-aniline)-grafted gum ghatti based nanospikes

In this work, we have synthesized poly(acrylamide-aniline)-grafted gum ghatti based crosslinked conducting hydrogel via a two-step synthesis method. The first step involved the microwave assisted synthesis of a semi-interpenetrating polymer network (semi-IPN) based on acrylamide and gum ghatti using N,N′-methylene-bis-acrylamide and ammonium persulfate as a crosslinker-initiator system. The semi-IPN has been observed to exhibit as much as 2183% swelling in aqueous solution. The effect of several variables such as time, solvent, pH, microwave power, crosslinker amount, aniline concentration, initiator concentration and monomer concentration on the swelling capacity was explored. In the final step, polyaniline was entrapped within a semi-IPN (optimized reaction condition) followed by doping with hydrochloric acid, which leads to the formation of conducting IPN. The synthesized hydrogels, as monitored by the swelling behaviour were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. Finally, the synthesized crosslinked networks have been used in malachite green (MG) adsorption. The result indicates that IPN of poly(acrylamide-aniline)-grafted gum ghatti are potential candidates for dye removal from water.