New chitin-based polymer hybrids, 4: Soil burial degradation behavior of poly(vinyl alcohol)/chitin derivative miscible blends

Soil burial degradation behavior of miscible blend systems of poly(vinyl al cohol) (PVA)/partially deacetylated chitin (1), PVA/chitin-graft-poly(2-met hyl-2-oxazoline) (2), and PVA/chitin-graft-poly(2-ethyl-2-oxazoline) (3) wa s investigated in comparison with the case of a pure PVA film. The degradat ion of the blend films was followed by the weight changes, scanning electro n microscopic observation, Fourier transform infrared spectroscopy, H-1-NMR , and size exclusion chromatography analyses. The rate of weight decrease i n these PVA/chitin derivative hybrids was higher than that of control PVA i n the soil burial test. Fourier transform infrared spectra of the recovered samples of the blends showed an apparent increase of the absorption intens ity due to beta-diketone structure in PVA, which reflects the progress of b iodegradation of PVA by PVA-oxidizing enzymes. Scanning electron microscopi c observation revealed that these blend films were degraded by bacteria and actinomycetes. The triad tacticity and number-average molecular weight of PVA in the hybrids after soil burial determined by H-1-NMR and size exclusi on chromatography, respectively, were almost the same as those before soil burial. These results suggested that enzymatic degradation of the hybrid fi lms occurred mainly on the surface and that degradation of the PVA-based sa mples in the soil was accelerated by blending the chitin derivatives. (C) 1 999 John Wiley & Sons, Inc.