Morphology and enzymatic degradation of poly(ϵ‐caprolactone) single crystals: does a polymer single crystal consist of micro‐crystals?

Abstract

Solution‐grown lamellar single crystals of poly(ϵ‐caprolactone) (PCL) were prepared from a dilute solution of n‐hexanol by the isothermal crystallization condition or the self‐seeding method. Hexagonal‐shaped lamellar crystals with and without spiral growth were obtained, and the crystals produced well‐resolved electron diffraction diagrams. The chain‐packing structure and morphological complexity in lamellar crystals were investigated by bright‐field and dark‐field diffraction contrast methods of transmission electron microscopy. Based on both diffraction contrast images, it was revealed that both tightly and loosely chain‐packing regions exist in one lamellar crystal. Thus, it was emphasized that PCL solution‐grown lamellar single crystals consist of micro‐crystals with nano‐order size for the crystalline core region. Lipase type XIII from Pseudomonas sp was used for the enzymatic degradation of the PCL lamellar crystals. Enzymatic degradation progressed perpendicularly from the crystal lateral sides, without decrease of the molecular weight and lamellar thickness, yielding notched‐shaped morphologies to the crystals. These results further indicate that PCL lamellar crystals consist of nano‐order micro‐crystals, and that enzyme hydrolyzes the loosely chain‐packing regions between the tightly chain‐packing regions (micro‐crystal regions). © 2002 Society of Chemical Industry

Molecular packing and crystalline morphologies of biodegradable poly(alkylene dicarboxylate)s derived from 1,6-hexanediol

“…Striations have also been reported for some polyesters (i.e. polyester 4-6 [9], polyester 12-10 [22], poly-b-propiolactone [23] and poly-3-caprolactone [24]), and different explanations have been given [24]. For example, striations may arise from the existence of different chain-packing states in the crystal or from a twinning involving a small chain axis shear of molecular chains.…”

Crystallization of Cyclic Polymers

“…The most important findings of Su et al [47] were that the morphology of C-PCL and L-PCL single crystals was similar [59], but that there were differences in the degree of truncation and in the average lamellar thickness. Figure 1 presents selected TEM micrographs and electron diffraction patterns of linear and cyclic 5.1 kg/mol PCLs [47].…”

Biodegradable polyesters reinforced with triclosan loaded polylactide micro/nanofibers: Properties, release and biocompatibility

“…In all cases, very intense reflections corresponding to each poly- ester, together with amorphous halos and the above peaks associated with cold crystallized PLA, were observed. Thus, PCL samples showed peaks at 0.566, 0.416, 0.403 and 0.373 nm, which correspond to the (102), (110), (111) and (200) reflections of polycaprolactone [25,26] whereas both P99 and COP samples showed peaks at 0.412 and 0.373-0.370 nm, which are indicative of similar molecular packing arrangements. In all cases, the relative intensity of PLA reflections slightly increased when using nanofibers whereas the relative intensity of the polyester matrix reflections remained almost constant.…”