Biopolymers: The eco-friendly substitutes of plastics
What are polymers and biopolymers?
Polymers are compounds made of repeating units called monomers. They are derivatives of petroleum which consist of long carbon chains. They are used in daily life such as polyethene, nylon, bakelite etc. Polymers naturally produced in single celled organisms (bacteria) or multicellular organisms (like plants and animals) are called biopolymers. They include polysaccharides, and polyamides. In nature silk, DNA, and protein are examples of biopolymers.
Origins:
Biopolymers are synthesized in cells via enzymatic pathways and known for being biodegradable and eco-friendly. They are produced industrially in bacteria or plant cells. Production can be natural or by genetic modification of the cells. They rival petroleum derived polymers like plastics and two widely used biopolymers are polylactic acid and cellulose.
Polylactic acid: The all-in-one biopolymer
The easiest way to recognize PLA is biodegradable plastic sheets. PLA is a polymer of lactic acid monomer and added into plastic sheets making them biodegradable. Lactobacillus is a natural producer of PLA and synthesizes it by ring-opening polymerization where cyclic carbon ring is straightened using a catalyst. Its usage as thermoplastics is popular given its higher melting point and shear modulus. It cannot withstand sudden shock and stress, however, it excels in stiffness. PLA is used as thermoplastics for food packaging, disposable biodegradable water bottles, dissolvable implants, as well as 3D printing. In the biomedical industry PLA is used as implants which easily break down to lactic acid in our body which is non-toxic as we produce it too. Moreover, PLA is less energy intensive and easy to produce in comparison to polymeric materials from petroleum-based sources, yet possesses the same advantages. Lastly, PLA is hydrophobic which provides great applications for waterproofing.
Cellulose: The versatile biomaterial
Cellulose is a biopolymer synthesized from glucose monomers in plants. It possesses properties of low thermal expansion coefficient, being lightweight yet strong and can be made into fibers. Cellulose was already used to make paper however, as a biopolymer it can be used for packaging, antimicrobial use and as a stabilizer in water-based products or cosmetics. It is used as chelating agent for water purification due to many hydroxy groups present to remove metal ions in water. Cellulose can be made into cellulose nanofibers which can be coupled with zinc oxide or silver nanoparticles which display antibacterial properties. Furthermore, biofilms can be made for this purpose to administer drugs. Finally, they can be used as filters that are impermeable to gas hence can be used in packaging industry for insulation.
Why biopolymers and its future:
Biopolymers are biodegradable in nature in comparison to petroleum derived plastics. Biopolymers being unstable can undergo controlled decomposition. In drug delivery, the outer capsule can be made of biopolymers which dissolve in your body at a controlled rate and becomes non-toxic. Additionally, they can be made as composite polymers to increase its mechanical strength. Considering the higher thermal capacities, they can be used successfully in electronic devices. Presently, the biomedical industry uses biopolymers for tissue engineering as scaffolds supporting tissue growth.
Going ahead biopolymers has the potential to dominate over conventional petroleum-based plastics and contribute to a green future.
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