To design a biodegradable polymer that can be used as a sustainable alternative to single-use plastic bags, we can consider using polylactic acid PLA as the base material. PLA is a biodegradable and bio-based polymer derived from renewable resources like corn starch or sugarcane. It has similar mechanical properties to polyethylene, which is commonly used in plastic bags, making it a suitable alternative.Here is a detailed synthesis route for the production of PLA:1. Fermentation:The first step in the production of PLA is the fermentation of plant-based feedstock, such as corn starch or sugarcane, to produce lactic acid. This process involves the use of microorganisms, such as Lactobacillus, to break down the carbohydrates in the feedstock into lactic acid.2. Purification:The lactic acid produced in the fermentation process needs to be purified before it can be used to produce PLA. This can be achieved through a series of filtration, evaporation, and crystallization steps to remove impurities and concentrate the lactic acid.3. Oligomerization:The purified lactic acid is then oligomerized to form low molecular weight pre-polymers called lactide oligomers. This process involves heating the lactic acid under vacuum conditions to remove water and promote the formation of ester linkages between lactic acid molecules.4. Lactide formation:The lactide oligomers are further heated under vacuum to produce cyclic lactide monomers, which are the building blocks for PLA. This process, called depolymerization, involves the removal of water and the formation of cyclic ester linkages.5. Ring-opening polymerization:The cyclic lactide monomers are then polymerized to form PLA through a process called ring-opening polymerization. This involves the use of a catalyst, such as tin II 2-ethylhexanoate, to initiate the reaction. The cyclic lactide monomers are opened and linked together to form long chains of PLA.6. Purification and processing:The resulting PLA polymer is purified through a series of filtration and precipitation steps to remove any residual catalyst and impurities. The purified PLA can then be processed into the desired form, such as pellets or fibers, which can be used to manufacture biodegradable plastic bags.In summary, the production of PLA involves the fermentation of plant-based feedstock to produce lactic acid, followed by a series of purification, oligomerization, lactide formation, and polymerization steps to produce the final PLA polymer. This biodegradable polymer can be used as a sustainable alternative to single-use plastic bags, helping to reduce plastic pollution and promote a circular economy.