Synthesis and Characterization of Novel Solubility Switching Trigger Degradable Plastics: Trihydrofuran and Trihydropyran Modified Dextran

Abstract

Plastics of all kinds are ubiquitous in our world; the accumulation of which causes a high environmental impact. Worldwide, eight billion tons of plastic waste have been generated, only 10% of which is recycled. Additionally, plastics can have a long life, anywhere from 20 to 500 years before they break down. This problem reveals the need for more sustainable materials. To address this, ‘green’, degradable, plastics have become widespread. One approach to create plastic materials has been through the irreversible chemical modification of ubiquitous functional groups on natural polysaccharides. But these bioplastics have drawbacks including narrow degradation conditions and undesirably long degradation timelines. To address this, I have designed a modified natural polymer with a trigger sensitive functional group that can catalytically hydrolyze in mildly acid conditions, reverting the plastic back into a natural polysaccharide. Dextran is an ɑ-1,6-glucan that, when modified with protective acetals, becomes insoluble in aqueous solutions. When treated with acid, the acetals undergo hydrolysis and degrade, allowing the polymer to revert into water-soluble dextran. Previous work includes the synthesis of acetal modified dextran, but this material lacks the desired plastic properties. Here, the synthesis and characterization of dextran modified with dihydropyran and dihydrofuran to produce the desired physical properties of existing synthetic plastics is reported. Both materials were also found be thermoplastic, a property unique to this material among other modified polysaccharides with triggered degradation. The ability to melt these materials opens myriad possibilities for forming and shaping them. Lastly, the structures of the materials are characterized by NMR and the materials’ degree of modification and degradation time are quantified.