This article will discuss natural polymer nanocomposites and their sources, touching on the applications these sustainable sources of nanomaterial can advance.
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Polymers are macromolecules composed of simpler repeating structural units linked together by covalent bonds. Natural polymers exist in nature as biomolecules and compounds that make up the body of living beings.
Many natural polymers such as cellulose or proteins form stable aggregates in the form of fibers or cellular structures in the presence of water, similar to reversible hydrogen bonding.
How Natural Polymers Are Used in Nanocomposites
Nanocomposites are made up of a matrix. Fillers are then mixed into this matrix based on the attributes that need to be enhanced.
Nanocomposites are classified as ceramic matrix nanocomposites, polymer matrix nanocomposites, or metal matrix nanocomposites based on the matrices employed.
The structure of polymer nanocomposites is characterized by the presence of particle size, which is up to 100 nanometers. The inclusion of nanosized particles in a polymer can have two principal consequences.
Firstly, this leads to a change in the properties of the polymer matrix itself and, secondly, to the acquisition of new properties by immobilized nanosized particles. The main properties of composites are significantly affected by the nature and characteristics of the polymer.
Applications of Nanocomposites
Natural polymer nanocomposites have recently received more attention than synthetic polymers because of their nontoxicity, compatibility, and biodegradability with cells and tissues.
These nanocomposites are well-suited for a variety of industrial and biological applications. They not only meet the unique needs of businesses due to their superior thermal properties, specific strength, ease of separation, better energy recovery, recyclability, and availability at low cost.
By combining natural polymers with antimicrobial nanoparticles like gold, zinc and copper, antimicrobial nanocomposites can be created that are useful in various industrial and medical applications.
For bone tissue engineering, biodegradable starch nanocomposites have been developed. Bone cement based on starch can provide immediate structural support and disintegrate upon contact. Additionally, they can be combined with bioactive particles to aid bone production at the cement–bone interface.
How are Natural Polymer Nanocomposites Sourced and Synthesized?
Nanocomposites can be obtained by different methods, and their properties will depend on the method used for their preparation. The most commonly used methods are solvent intercalation, in situ polymerization, and fusion intercalation.
Mixing the nanomaterial and monomer in solution, where polymerization of the monomer occurs, is referred to as in situ polymerization. Solvent intercalation occurs when the nanomaterial and polymer interact in a solution. The polymer chains intercalate and migrate within the nanomaterial sheet in the solvent, creating the polymer nanocomposite by solvent removal.
In melt intercalation, the nanomaterial and polymer are joined above the polymer's melting point and are kept at that temperature for an extended period. Then, the material is subjected to shearing or other conditions to stimulate nanomaterial intercalation.
Melt intercalation is the most desirable of these technologies due to its versatility and compatibility with existing polymer processing equipment, as well as its environmental friendliness due to the absence of solvents. Additionally, this procedure enables the use of polymers that are not amenable to in situ polymerization or solvent intercalation.
Main Sources of Natural Polymer Nanocomposites
Starch is a naturally renewable polymer, and it has enormous potential due to its total compostability, biodegradability, biocompatibility, and lack of hazardous residues. However, it has a few drawbacks like high water sensitivity, weak mechanical properties, and poor processability. Incorporating nanofillers into starch nanocomposites leads to significant modifications in the stability and applicability of starch-based nanocomposites.
One of the most important applications of starch-based nanocomposites is creating environmentally friendly biodegradable material. The starch-based nanocomposites have a strong oxygen barrier and biodegradability, are relatively cheap and extensively found in nature.
Cellulose Based Nanocomposites
Cotton is the purest form of natural cellulose, and it is also one of the most prevalent organic substances on the planet. The main component of paper made from tree wood and the supporting components in leaves and plants is cellulose. It is a polymer produced from glucose monomers.
Simple or pure cellulose can be transformed using modern technologies to produce nanocellulose composites in a variety of forms, such as cellulose acetate, bacterial nanocellulose, and cellulose nanofibers which are all high-tech materials. Low manufacturing yields and economic constraints are preventing these technologies from entering the market.
Chitin Based Nanocomposites
It is the world's second most prevalent polymer, naturally created by many living species. Chitin occurs naturally in nature as crystalline microfibrils found in the cell walls of fungus, yeast, and arthropod exoskeletons. Chitin is used as a filler in a gelatin-based protein matrix to form natural polymer nanocomposites.
These composites are employed in tissue engineering and bone regeneration. It can also be used to make fibers when mixed with a protein complex. Chitin can be easily transformed into beads, gels, nanofibers, sponges, and scaffolds. In nanobiotechnology, cancer medication, tissue engineering, and wound dressing, these shapes have a wide range of applications.
Future Developments
Natural polymer nanocomposites have many uses, which are continuously expanding due to their unique features, low cost, and ease of fabrication. In the future years, these are likely to significantly impact environmentally conscious strategies aimed at contributing to sustainable scientific practice.
References and Further Reading
João, C. F. C., Silva, J. C., & Borges, J. P. (2015). Chitin-based nanocomposites: biomedical applications. In Eco-friendly polymer nanocomposites (pp. 439-457). Springer, New Delhi. DOI: https://doi.org/10.1007/978-81-322-2473-0_14
Kalia, S., Dufresne, A., Cherian, B. M., Kaith, B. S., Avérous, L., Njuguna, J., & Nassiopoulos, E. (2011). Cellulose-based bio-and nanocomposites: a review. International journal of polymer science, 2011. https://doi.org/10.1155/2011/837875
Medeiros, E. S., Dufresne, A., & Orts, W. J. (2010). Starch-based nanocomposites. Starches: Characterization, properties, and applications, 205-251. Retrieved from https://www.researchgate.net/publication/216091637_Chapter_8_-_Starch-based_Nanocomposites
Tavares, M. I. B. , Silva, E. O. d. , Silva, P. R. d. , & de Menezes, L. R. (2017). Polymer Nanocomposites. In (Ed.), Nanostructured Materials - Fabrication to Applications. IntechOpen. https://doi.org/10.5772/intechopen.68142
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