Biodegradable PVA–Alginate Bio-Based Polymers Incorporating Cardanol-Based Polyols for Antibacterial Applications

The extensive use of petroleum-based plastics has caused serious environmental concerns; thus, the need for biodegradable alternatives is essential. Here, we present eco-friendly bio-based polymers prepared by crosslinking poly(vinyl alcohol) (PVA) and alginate (ALG) with glutaraldehyde, while incorporating cardanol-derived polyols (PCD) to add antibacterial functionality. The synthesized bio-based polymers were characterized by FT-IR, XRD, and TGA. FT-IR confirmed sufficient crosslinking between PVA and ALG, whereas XRD revealed a minor decrease in crystallinity. Thermogravimetric analysis showed enhanced thermal stability with increasing ALG contents, as the residual mass increased from 8 wt% (PVA only) to 19-31% (PVA:ALG = 80:20-60:40). Swelling behavior was strongly governed by ALG, with higher ratios promoting water uptake up to 130%, whereas PCD reduced swelling due to increased hydrophobicity. Antibacterial assays indicated complete inactivation of <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> within 10-60 min depending on the polymer composition. These results demonstrate that tuning the PVA:ALG ratio and PCD content allows precise control of physicochemical properties. Overall, the developed PVA-ALG/PCD bio-based polymers represent a versatile and sustainable platform for eco-friendly packaging, biomedical, and water treatment applications.