Relationship between twisting phenomenon and structural discontinuity of stacked lamellae in the spherulite of poly(ethylene adipate) as studied by the synchrotron X-ray microbeam technique

Abstract

Wide-angle and small-angle X-ray scattering measurements were performed simultaneously using an X-ray beam 1 μm in size to detect the inner structure of a spherulite of poly(ethylene adipate) [PEA, –(O(CH2)2OCO(CH2)4CO–)n–]. The lamellae were found to twist periodically by 180° in the area between the neighboring bright rings observed in the polarized optical microscope image of the spherulite. However, as known from the discontinuity between the repeated lamellar zones discovered by Woo et al. (Macromolecules, 45:1375–1383, 2012), the twisted lamellae must not be assumed to be continuously twisted long plates spreading out over the spherulite. Rather, these lamellae should be considered to have limited areas of ~7 μm in length along the radial direction and with disconnected end zones. The present X-ray scattering data revealed the structural relation between the repeated arrays of the disconnected lamellar blocks and the 180° twisting phenomenon, which occurs only in the finite and disconnected flat-on lamellar zones. Designer supramolecular polymers are a growing field of polymer materials. The designability and flexibility in their structures and functionality have attracted a great deal of attention in polymer science, as well as in supramolecular chemistry. These polymeric structures are formed from one or more molecular components via reversible bonds; therefore, monomeric and polymeric states are in equilibrium on the relevant experimental timescale. The dynamic nature of supramolecular polymers in terms of chain lifetime and conformational flexibility are determined by external conditions. This adaptivity can result in stimuli-responsive structures and properties. This article describes the use of our host–guest structures based on a calix[5]arene, a bisporphyrin, and a self-assembled capsule in the synthesis of supramolecular polymers.