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Hydrolytic degradation of polyurethane has been achieved using lipase as catalyst. The degradation of polyurethane containing an aliphatic polyester chain as soft segment rapidly took place in the presence of Candida antarctica lipase in toluene at 60 °C to give oligomers with molecular weight less than 500.

ABSTRACT:The reduced viscosity of linear and branched polyethylenimine (LPEI and BPEI, respectively) was measured at various pH and ionic strength to examine the effects of the micro-structure. The viscosity value of LPEI decreased with increasing pH (pH> 2) in the absence or presence of a salt (NaCI). The larger the ionic strength in the aqueous solution of LPEI, the smaller the viscosity value of LPEI. On the other hand, the viscosity of BPEI changed little over the wide range of pH 2-10. LPEI and BPEI gels were prepared by cross-linking with a bis-epoxide. The swelling-contraction behaviors of these gels were examined at various pH, ionic strength, and metal ions (Cu2+ and Ni2+) concentration. The LPEI gel showed a large response with respect of these factors. The response of the BPEI gel, however, was much smaller than that ofLPEI gel.KEY WORDS Linear Polyethylenimine / Branched Polyethylenimine / Micro-Structure / Viscosity Behavior / Polyethylenimine Gel / SwellingContraction Behavior / Polyamines are known to form chelating complexes with various metal ions. We have already reported quantitative investigations on the chelating abilities of polyamines, linear polyethylenimines and branched polyethylenimines (LPEI and BPEI, respectively),l poly-(vinylamine) (PVAm),2 and poly(allylamine) (PAAm), 3 which provide a full set of primarily different micro-structures for amine functional groups. During the the course of these studies, the chelating abilities and viscosity behaviors of these 'polyamines are found to be closely related with the micro-structures. Moreover, we have recently found a dramatic viscosity change of PV Am with respect to pH change, ionic strength, and cupric ion concentrations. 4 A PV Am gel prepared by using a epoxide as a cross-linking agent has been found to show a good response to these factors. 4 LPEI has only secondary amino groups in the main chain. A commercial BPEI, on the contrary, contains primary, secondary, and tertiary amino groups in a ratio of approximately 25%,50%, and 25%, respectively.s In this study we report viscosity behaviors of LPEI and BPEI and the swelling-contraction behaviors of LPEI and BPEI gels with varying pH, ionic strength, and metal ion concentrations.

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