Development of functional degradable materials by precise crosslinking design of biobased polymers

Petroleum-based plastics are lightweight and durable and exhibit excellent formability. However, the increase in global plastics production, coupled with the economic development of emerging countries, and the resulting marine pollution caused by plastic waste have become serious problems in recent years. Polysaccharides, such as starch and cellulose, are the most abundant biopolymers in nature and are particularly promising plastic alternatives owing to their renewability, sustainability, and biodegradability. However, owing to their lack of water resistance and adequate mechanical properties, large-scale application of polysaccharide films in single-use plastics is limited because water resistance is preferred in many daily scenarios. Further research is required to optimize bioplastics to make them economically and practically feasible. In this report, we focus on stimuli-responsive materials that form or dissociate cross-linked structures in response to slight changes in external stimuli or the environment. We developed starch-based films with different disintegration/dissolution rates in freshwater and seawater as environmentally friendly materials. Modified starch was mixed with oxidized cellulose or a water-soluble polymer to prepare a transparent, homogeneous film. After the introduction of hydrogen bonds, the starch complex film was stable in freshwater; however, in seawater, the hydrogen bond crosslinks dissociated, causing the film to dissolve rapidly. This technology balances degradability in marine environments with water resistance in everyday environments, providing an alternative means of reducing marine plastic pollution, and it is expected to be applied in a variety of industrial sectors.