Controlled biodegradability of polyhydroxybutyrate via surface coating with cellulose triacetate

Polyhydroxybutyrate (PHB) is widely used in disposable plastic products because of its high biodegradability; however, its use in long-term applications is limited by premature degradation. This study presents a strategy to control PHB biodegradation by coating its surface with cellulose triacetate (CTA) and selectively removing the coating through alkaline treatment. The CTA coating acts as a biodegradable barrier, delaying microbial attachment and suppressing degradation under natural conditions. After alkaline treatment, the surface acetyl groups are partially removed, increasing hydrophilicity and enabling microbial colonization, thereby initiating degradation. The experimental results revealed that the CTA-coated films did not biodegrade in marine environments (20, 25 °C), whereas the TCTA-coated films (CTA-coated films after alkaline treatment) achieved 19% biodegradation at 20 °C and 56% biodegradation at 25 °C within 30 days. Under composting conditions (50 °C, 55% relative humidity), the TCTA-coated films fully degraded within 10 days, and the CTA-coated films gradually degraded without further treatment. The approach offers potential for applications requiring delayed or on-demand degradation, such as marine-disposable items, agricultural films, and smart packaging.