SOLUTIONS

Starch and cellulose are the most abundant and important representatives of renewable biomass. Since the mid-19th century their properties have been changed by chemical modification for commercial and scientific purposes, and there substituted polymers have found a wide range of applications.  However, the inherent polydispersity and supramolecular organization of starch and cellulose cause the products resulting from their modification to display high complexity. Cellulose in its native form is not soluble in water. It can be rendered water-soluble by chemical reaction of its hydroxyl groups with hydrophilic substituents. In this manner water-soluble cellulose derivatives such as carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), methyl cellulose (MC), and hydroxypropyl cellulose (HPC) are produced.

Bibliography: (1) L.-M Zhang, “Cellulosic associative thickeners“, Carbohydrate Polymers, 2001. (2) Petra Mischnick, Dane Momcilovic, “Chemical Structure Analysis of Starch and Cellulose Derivatives“, Advances in Carbohydrate Chemistry and Biochemistry, 2010.

Chitin is the second most abundant biopolymer after cellulose and is a resourceful copious and cheap biomaterial discovered in 1859 owing to significant industrial and technological utility. Chitosan is the derivate of chitin by removing enough acetyl groups with diluted acids or strong bases. The degree of deacetylation is a quality parameter of chitosan describing the percentage of acetyl groups removed from chitin. The degrees of deacetylation depend on the raw material and preparing method. Chitin with a deacetylation degree of more than 55% is generally referred to chitosan. Chitosan endures assorted chemical/physical modifications easily at free proactive functionalities, yet intact bulk properties are achieved through processing, viz., film, membrane, composite, hybrid, nanofibre, nanoparticle, hydrogel and scaffolds.

Chitosan-matrix is advantageous over biopolymers due to inherent economic, versatile and unequivocal portfolio from bio-molecule to quantum dots which traced its great journey in modern S&T. Overall, chitosan chemistry boosted R&D in countless domains like agriculture, biochemical, medicine, pharmaceutics, nanotechnology, biotechnology, material/food science, microbiology, biomedicine, bioengineering, biochemistry, bioprocessing and environment.

Weiping Su, Shaoqi Yu, Daidai Wu, Meisheng Xia, Zhengshun Wen, Zhitong Yao, Junhong Tang, Weihong Wu, “A critical review of cast-off crab shell recycling from the perspective
of functional and versatile biomaterials” Environmental Science and Pollution Research (2019).

Natural gums (Arabic gum, Karaya gum, and Guar gum) are complex polysaccharide and soluble dietary fibre obtained from various tree species that exhibit unique and diverse physical properties. These extracts are widely used in the textile, pharmaceutical, cosmetics, and food industries due to their different functional properties in a wide range of applications.
Arabic gum is derived from the exudation of stems and branches of Acacia Senegal L. and It is known to be the most widely used exudate gum. It has become an important ingredient for food and other industries, as it provides good emulsion stability, encapsulation properties, and high solubility. Meanwhile, Guar gum is considered as one of the best thickening, emulsifying, and stabilizing additives, in which it contains several hydroxyl groups and displays a polymeric structure. On the other hand, Karaya gum exhibits a very strong swelling, high viscosity, and very poor solubility properties because of its acetyl groups; thus, its applications are limited only in cosmetic and pharmaceutical industries.

Rosland Abel, SE, Yusof, YA, Chin, NL, et al. “The effect of particle size on the physical properties of Arabic gum powder.” J Food Process Eng. 2020

Xanthan gum is a water‐soluble anionic polysaccharide produced by aerobic fermentation with Xanthomonas campestris. Xanthan gum consists of D‐glucose, D‐mannose, and D‐glucuronic acid units in its structure. It is stable over a wide pH range. Xanthan gum’s film‐forming properties comprise pseudo‐plastic rheological behaviour in an aqueous environment that is amenable to film fabrication because it readily disperses in cold or hot water with minimal effect on its viscosity from either temperature or pH. Xanthan gum was reported to be a compatible cross‐linker to be blended with various materials.

Agar is a polysaccharide that consists of agarose (gelling fraction) and agaropectin (nongelling fraction). It is extracted from the marine algae of class Rhodophyceae such as Gelidium sp. and Gracilaria sp. The most important attribute of agar is its ability to form solid gels at very low concentrations. Agar is more stable at low pH and high‐temperature environment conditions. Agar has good film‐forming properties. As it is also renewable and biodegradable, it has been tested to prepare different materials like foams, films, and coatings.

Rukmanikrishnan, B, Rajasekharan, SK, Lee, J, Lee, J. “Biocompatible agar/xanthan gum composite films: Thermal, mechanical, UV, and water barrier properties.” Polym Adv Technol. 2019.

Animal glue, as a non-toxic, biodegradable natural polymer material, which is derived primarily from collagenous material present in animal hide or from the extraction of collagen present in animal bones, primarily cattle. Animal glue has excellent environmental performance, this aspect has incited considerable research interest from industries and institutions.

Animal glue is an organic colloid of protein formed through hydrolysis of the collagen, similar to gelatin. The word collagen itself derives from Greek κόλλα kolla, meaning ‘glue’.

By catalytic decomposition, the peptide molecular structure of the animal glue can be decomposed into a smaller molecular structure that exhibits a liquid state at room temperature and is easily chemically modified and used as an adhesive, sizing and coating, and for colloidal applications in industry.

WANG, T.-S.; LIU, W.-H.; LI, Y.-M. “Preparation of animal glue binder treated by anhydrous sodium carbonate“. Journal of Adhesion Science & Technology, 2018.

Poly(vinyl alcohol) is the most commercially important water soluble plastic in use. It is tasteless, odourless, it will biodegrade and is biocompatible. As well as being soluble in water, it is slightly soluble in ethanol, but insoluble in other organic solvents. Polyvinyl alcohol (polyvinylalcohol) has a variety of applications ranging from paper and textile industries to construction, adhesives and the oil and gas industry. Polyvinyl alcohol is water-soluble, has specific colloidal characteristics, excellent film-forming properties, and high tensile strength. In additi­on, it is elastic and resistant to heat and organic solvents. Polyvinyl alcohol flexibility is due to its chemical properties, especially the numerous hydroxyl groups that react with substances such as reactant resins. It is also be readily blended with a number of natural materials and can exhibit properties that are compatible with a range of applications. The inclusion of natural fibres and fillers can give further improvements in mechanical properties without compromising overall degradability. Therefore, the potential benefits of this material given its water-soluble characteristics are huge, but this must be offset against practical considerations of its long-term life cycle in changeable environmental conditions.

WANG, T.-S.; LIU, W.-H.; LI, Y.-M. “Preparation of animal glue binder treated by anhydrous sodium carbonate“. Journal of Adhesion Science & Technology, 2018.

Water soluble polymer flocculants are important constituents of solid–liquid separation units for the treatment of a variety of process-affected effluents. The systematic development of a flocculant relies on a good understanding of flocculation process, polymer synthesis, polymer characterization, and, not the least, flocculation performance assessment as desired for a particular treatment process, all of which are essential to establish meaningful relationships between flocculant microstructure and flocculation efficiency.

Synthetic flocculants are made by polymerization of water soluble monomers. Depending on the monomer(s) used, synthetic flocculants may be classified based on their charges as positively charged, negatively charged, neutral, or, in some cases, amphoteric. They may alternatively be classified according to their architecture as linear, branched, hyperbracnhed, or grafted. Polyacrylamide is the most important water soluble nonionic flocculant because its monomer, acrylamide, is highly water soluble, cost-effective, and very reactive.

VAJIHINEJAD, V. et al. “Water Soluble Polymer Flocculants: Synthesis, Characterization, and Performance Assessment.” MACROMOLECULAR MATERIALS AND ENGINEERING, 2018.

Superabsorbent polymer materials (SAPs) are cross-linked polymer networks constituted by water-soluble building blocks. SAPs are generally composed of ionic monomers and are characterized by a low cross-linking density, which results in a large fluid uptake capacity, up to 1000 times their own weight. Interestingly, these superabsorbent networks can absorb and retain aqueous solutions up to several hundred times their own weight, while even retaining it under pressure.
Typical monomers applied in synthetic SAP development include among other: acrylic acid (AA), acrylamide (AM), methacrylic acid (MAA), dimethylaminoethyl methacrylate (DMAEMA), dimethylaminopropyl methacrylamide (DMAPMA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS). They can be introduced into a cross-linked (co)polymer network using a synthetic cross-linker such as N,N’-methylene bisacrylamide (MBA).
Semi-synthetic or semi-natural SAPs can be synthesized by the addition of a synthetic constituent to a natural, polymeric backbone through graft polymerization. In the latter case, the natural backbone is acting as a natural cross-linker for the synthetic monomers. Natural SAPs include polysaccharides and proteins.

Both synthetic and polysaccharide-based SAPs have already been used for a multiplicity of applications such as diapers, the biomedical field, agriculture. Finally, ‘smart’ SAPs are often useful for biomedical applications such as drug release as they can target a certain in vivo location exerting particular characteristics triggering the release of the encapsulated/coupled drug.

MIGNON, A. et al. “Superabsorbent polymers: A review on the characteristics and applications of synthetic, polysaccharide-based, semi-synthetic and ‘smart’ derivatives.” European Polymer Journal, 2019.

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