Controlling the structure and properties of semi-crystalline cellulose/silk-fibroin biocomposites by ionic liquid type and hydrogen peroxide concentration

This work reports how to tune the semi-crystallinity of a blended microcrystalline cellulose/silk-fibroin biocomposite using ionic liquids and various coagulation agents. The morphological and thermal properties of a blended 1:1 polymeric system are studied as a function of polymer fabrication parameters. Ionic liquids, 1-ethyl-3-methylimidazolium acetate verses 1-ethyl-3-methylimidazolium chloride, are used as competing solvent types and six hydrogen peroxide solutions (1—25%) plus water are used as varying coagulation agents. Analysis of the results demonstrate that solvent anion type, Ac⁻ verses Cl⁻, affects protein secondary structure formation, and that solvent anion type and the concentration of hydrogen peroxide changes morphology and thermal stability of the regenerated materials. Polymers dissolved in 1-ethyl-3-methylimidazolium acetate are less thermally stable than those dissolved in 1-ethyl-3-methylimidazolium chloride. Furthermore, carbohydrate microcrystal size is positively correlated to hydrogen peroxide concentration upon fabrication and is calculated to have either a gradual or step transition increase in microcrystal size depending upon the solvent's anion type.