Enzymatic degradation of poly(octamethylene suberate) lamellar crystals

Abstract

Enzymatic degradation of poly(octamethylene suberate) single crystals was investigated by electron microscopy. Different lamellar morphologies were obtained using 2.5-hexanediol as a solvent and at a temperature between 42 and 51 °C. Crystals with a different degree of truncation and with monolayer or bilayer organization were analyzed. Lipases from Rhizopus oryzae were found to be highly effective in degrading crystalline domains and showed different attack mechanisms. Thus, enzymes preferentially attacked the lateral crystal growth faces or the lamellar fold surfaces depending on the crystallization conditions. Temperature and indeed its fluctuation during the crystallization process were crucial to determine how degradation started and progressed. The most interesting results were obtained for single crystals characterized by a low degree of truncation and formed in crystallization baths with a small temperature oscillation. In this case, it was shown that degradation started on the folding surface of specific sectors and progressed along a preferred crystal direction.