Based on these observations, we conclude that the reduction in molecular weight observed by enzymatic hydrolysis is likely to occur via in-chain hydrolysis and at the sites of the aliphatic monomers rather than at the polymer end group. These results agree with the different hydrolysis rates that the enzymes exhibited toward aliphatic or aromatic homopolymers. It should be noted that the list of assignments is representative of the lower mass portion of the sample; however, we expect the same trend to apply to higher molecular weight species. processed in a semi-automated fashion using MSPolyCalc and based on the known polymer compositions. The data processing resulted in molecular formula assignments within a mass tolerance of 5 ppm and with good isotopic pattern match (within 95% similarity for isotopic zones up to A+3). All species were detected