Sustainable, thermoplastic and hydrophobic coating from natural cellulose and cinnamon to fabricate eco-friendly catering packaging

Non-degradable polymers cause serious environmental pollution problem, such as the widely-used while unrecyclable coatings which significantly affect the overall degradation performance of products. It is imperative and attractive to develop biodegradable functional coatings. Herein, we proposed a novel strategy to successfully prepare biodegradable, thermoplastic and hydrophobic coatings with high transparence and biosafety by weakening the interchain interactions between cellulose chain. The natural cellulose and cinnamic acid were as raw materials. Via reducing the degree of polymerization (DP) of cellulose and regulating the degree of substitution (DS) of cinnamate moiety, the obtained cellulose cinnamate (CC) exhibited not only the thermal flow behavior but also good biodegradability, which solves the conflict between the thermoplasticity and biodegradability in cellulose-based materials. The glass transition temperature (T_g) and thermal flow temperature (T_f) of the CC could be adjusted in a range of 150–200 ℃ and 180–210 ℃, respectively. The CC with DS < 1.2 and DP ≤ 100 degraded more than 60% after an enzyme treatment for 7 days, and degraded more than 80% after a composting treatment for 42 days. Furthermore, CC had no toxicity to human epidermal cells even at a high concentration (0.5 mg mL^-1). In addition, CC could be easily fabricated into multifunctional coating with high hydrophobicity, thermal adhesion and high transparence. Therefore, after combining with cellophane and paperboard, CC coating with low DP and DS could be used to prepare fully-biodegradable heat-sealing packaging, art paper, paper cups, paper straws and food packaging boxes.