Synergistic Modification of Carrageenan Films with Plasticizers and Cross-Linker: A Promising Approach to Tunable Functionalities

Multifunctional biobased films with improved physicomechanical properties were fabricated by incorporating glycerol (G), sorbitol (S), and potassium chloride (KCl) into a cost-effective kappa-carrageenan matrix. Both the plasticizers and the cross-linking agent were mixed with the polymer matrix to form uniform, smooth, and transparent high-quality films of thickness 0.060 mm. Key properties of these films could be fine-tuned by varying concentrations of glycerol and sorbitol, and were further enhanced by the addition of KCl. Of the materials tested, glycerol-containing films, with and without added KCl, exhibited optimum mechanical and water interactive properties for biomedical applications, especially for wound healing. Meanwhile, films incorporated with sorbitol and KCl exhibited superior tensile properties and the lowest hydrophilicity, an ideal combination for food packaging applications. In the case of uncross-linked sorbitol-containing films, a phase transition was observed at higher temperatures, leading to the formation of an immiscible phase that led to two distinct tan δ peaks due to the polymer chain mobility and their relaxation behavior. These results suggest that the highly versatile nature of carrageenan films can be effectively optimized by incorporating appropriate and readily available plasticizers and cross-linkers to suit a wide range of real-life applications, providing an attractive alternative to the currently used non-eco-friendly materials.