Dual-crosslinked starch/carboxymethyl cellulose blend film with ion-responsive dissolution properties

Abstract

While the ability of quickly vanishing in water has made starch-based plastics a potential solution to the current marine plastic issue caused by discarded single-use plastics, this ability also translates into lack of water resistance in daily scenario. Here, we aim to improve the water resistance of starch-based blend films in daily scenarios while allowing them to disintegrate and vanish rapidly in marine environments via the introduction of ionic crosslinks. A dialdehyde starch (DAS)/carboxymethyl cellulose (CMC) blend film is prepared via a modified solution casting process, during which DAS is gradually rendered cationic by a cationizing reagent, Girard's reagent T, and interacts with CMC to form ionic crosslinks. Meanwhile, the aldehyde groups on DAS also form acetal bonds with the -OH groups on both DAS and CMC, which further increases the wet strength. In solutions of low ionic strength encountered in daily life, such as freshwater, the film remains stable for both types of crosslinks. In high-ionic-strength solutions, such as seawater, the film swells rapidly and disintegrates owing to the cleavage of ionic crosslinks. This study demonstrated ionic crosslink could be a potential solution for balancing the protection of marine ecosystem and ease of use of starch-based blend films, which is essential to the development of future marine ecosystem-friendly single-use plastics.