Evaluation of biodegradation behavior of poly(ε-caprolactone) with controlled terminal structure by pyrolysis-gas chromatography and matrix-assisted laser desorption/ionization mass spectrometry

Abstract

The enzymatic degradation behavior of poly(ε-caprolactone) (PCL) with an α-benzyloxy terminal during an enzymatic degradation test using cholesterol esterase was evaluated complementarily by pyrolysis-gas chromatography (Py-GC) in the presence of tetramethylammonium hydroxide (TMAH) and matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). On the pyrograms of PCL samples, dimethyl derivative of ε-caprolactone and some related products originating from ε-caprolactone (ε-CL) units were observed together with those from benzyloxy terminal units such as benzyl methyl ether. The relative content of the benzyloxy terminal unit in the residual PCL sample after the degradation test, which was estimated from the relative intensities of the specific pyrolysis, considerably fell down especially in the initial stage of the degradation test. On the other hand, in the MALDI mass spectra, the observed molecular weight distribution of the PCL molecules having a benzyloxy terminal was substantially unchanged during the enzymatic degradation, while PCL molecules without benzyloxy terminal appeared at the lower mass region after the degradation test. These results suggested that the enzymatic degradation of the PCL might proceed mainly in the exo-cleavage mode from α-benzyloxy terminal side under a given condition. © 2003 Elsevier Science B.V. All rights reserved.