The use of bioplastics as alternatives to petroleum-based plastics has gained significant attention in recent years. These biomaterials are typically created by combining biopolymers like chitosan with plasticizers such as glycerol (Glyc). Previous research has shown that the amount and type of alcohol used can significantly affect the polymeric structure. Chitosan’s repeat unit, glucosamine (GlcN), and Glyc are key compounds in forming polyol solutions. Glycerol can have primary binding sites (1,2 or 1,3-OH) and secondary binding interactions due to its additional hydroxyl groups.

To explore the impact of primary binding on GlcN aggregation, ethylene glycol and (1,3)-propanediol were used to probe the 1,2 and 1,3 binding modes. Various diols, including (1,2)-propanediol, (2,3)-butanediol, and (2,4)-pentanediol, were analyzed to understand secondary binding while keeping primary interactions constant. This summer, additional polyols such as 2-methyl-(1,3)-propanediol and 2-(hydroxymethyl)-(1,3)-propanediol were tested to evaluate how an increased alcohol content affects GlcN aggregation and disaggregation.

Spectroscopic techniques, including dynamic light scattering (DLS), attenuated total-reflectance infrared spectroscopy (ATR-IR), and nuclear magnetic resonance (NMR), were used to analyze the intermolecular interactions between these diols and GlcN. While most of the analysis focused on ATR-IR, solutions of polyols like Xylitol, Sorbitol, and Mannitol were compared to diols and triols to assess their impact on binding and aggregation. Results indicate that a higher alcohol content leads to increased hydrogen bonding at the molecular level, with more significant hydrogen bonding observed in polymeric chitosan solutions than in glucosamine solutions.