Multilayer biodegradable films with a degradation initiation function triggered by weakly alkaline seawater.

• CTA (non-biodegradable) was coated onto PHBH (biodegradable) films. • Deacetylation of CTA by weak alkali is a degradation initiation function. • The coated films were deacetylated under weakly alkaline seawater conditions. • Finally, the deacetylated coated PHBH films begun to be degraded. A non-biodegradable polymer (cellulose triacetate; CTA) was coated on the surface of a biodegradable polymer film (poly(3-hydroxybutylate- co -3-hydroxyhexanoate); PHBH), and the multilayer coated films were characterized using microscopy and spectroscopic techniques. The enzymatic degradability of the CTA-coated PHBH films was compared with that of non-coated PHBH films in the presence of an enzyme mixture (cellulase and PHB depolymerase). Non-coated PHBH films were effectively degraded; however, the CTA-coated films were only slightly degraded, indicating that the CTA coating could suppress PHBH biodegradation during use. Surface-deacetylated coated films (with a degree of substitution of 1.3) could be degraded by the same enzyme mixture, indicating that the deacetylation of CTA in an alkaline environment can trigger the degradation of PHBH. Furthermore, degradation tests in seawater demonstrated that CTA was deacetylated under weakly alkaline seawater conditions, and the degradation of cellulose acetate on the surface exposed the PHBH underneath, thereby allowing PHBH degradation. Overall, the results suggest that CTA coatings can effectively serve to initiate the biodegradation of PHBH when released into the ocean. [ABSTRACT FROM AUTHOR]