Biodegradable polymer materials have become a hotspot in today's research, which refers to the ability of polymer materials to be degraded by microorganisms (such as fungi, bacteria, algae) or their secretions under the action of enzyme or chemical decomposition. Currently biodegradable polymers that have been commercialized mainly include aliphatic polyesters, polyethers, polyvinyl alcohols and polysaccharides. Biodegradable polymers can also be divided into chemical synthesis type, natural polymer type, blending type, and biosynthesis type according to their source.

Applications:

• Packaging industry: Among the various biodegradable packaging materials, polylactic acid has the largest and most potential application market. Polylactic acid is of high-level gas and water barrier properties, printability and transparency. And its basic raw material lactic acid is one of the inherent substances of the human body, which is non-toxic and harmless to the human body and thus has a broad prospect in the food packaging market.

Figure 1. Degradable polylactic acid

• Medical field: Biodegradable polymers have many uses in the medical field, especially in tissue engineering and drug delivery. The biodegradable polymer drug carrier can release the drug to a specific part of the body at its maximum load, then degrade into a non-toxic substance, and finally be metabolized from the body through its metabolism. During this period, the polymer slowly degrades into smaller molecules, releasing natural products, and has the ability to control the release of drugs. When the polymer degrades, the drug is slowly released. For example, "activating" tumors with degradable polymer-epirubicin conjugates can induce immunogenic cell death, which can be used in immunosuppressive tumor therapy. In addition, encapsulating the drug in a polymer and adding a targeting agent can reduce the drug's toxicity to healthy cells. Besides, biodegradable polymers are equally important for tissue regeneration engineering. They can be used to grow tissues and cells in vitro or used as biodegradable scaffolds to construct new structures and organs in vivo. For example, biodegradable scaffolds may have the advantages of reducing the immune response and suppressing foreign bodies.

Figure 2. Biodegradable polymer-doxorubicin is used in the treatment of immunosuppressive tumors.

• Agriculture field: Biodegradable polymer materials are also widely used in agriculture, such as plastic film, feed packaging bag, fertilizer, insecticide, hormone and seed coating film, fruit bagging, transplanting seedling pot. Plastic film is widely used because it can increase crop yield, reduce the use of herbicides and pesticides, and better maintain soil temperature, moisture and fertilizer. At present, the traditional plastic mulch film is mostly composed of low-density polyethylene (LDPE), high-density polyethylene (HDPE), PVC, PP, ethylene-vinyl acetate copolymer (EVA) and other materials, among which LDPE is the most widely used because of its good mechanical and optical properties. Many new types of degradable plastic films, such as photodegradable plastic film, biodegradable plastic film, photodegradable and biodegradable plastic film, liquid plastic film, plant cellulose plastic film, have been widely used in the field of agriculture. Among them, biodegradable plastic film and plant fiber plastic films have attracted more and more attention because they can be degraded completely.

References:

1. Zhu Yingxian. Chen Dajun, Li Yaojun.(2001) "Biodegradable fiber materials." Polymer bulletin.1:48-52.
2. Huang Hansheng.(1994) "Research and development trends of biodegradable plastics." New Chemical Materials, 5:1-6.