Evidence for Distinct Sectors in Polymer Single Crystals

Why do polyethylene crystals have sectors?

“…Highresolution electron microscopy and electron microdiffraction studies of such collapsed pyramids (10) have shown that alternating bands of tilted and untilted chains are found in these corrugations and the prominent reflections from the tilted chain areas are {110} Friedel pairs, with orientation of these tilt axes dependent upon the sector. In agreement with earlier studies (3)(4)(5)(6)(7)(8)(9), the probable chain-fold direction has been identified by surface decoration with polyethylene crystallites grown from polymer deposited from the vapor phase (11). It is also no surprise that lamellae of very long paraffins, which can be crystallized with a single "hairpin" chain fold, also are sectorized with a chain-fold orientation very similar to polyethylene (12).…”

“…As shown by extensive electron microscopic studies (3)(4)(5)(6)(7)(8)(9), large polyethylene crystals grown from dilute solution originally occur in suspension as hollow pyramids, which flatten onto a substrate surface to produce corrugations along the (130) direction in {110} sectors. Highresolution electron microscopy and electron microdiffraction studies of such collapsed pyramids (10) have shown that alternating bands of tilted and untilted chains are found in these corrugations and the prominent reflections from the tilted chain areas are {110} Friedel pairs, with orientation of these tilt axes dependent upon the sector.…”

Sectorization of a Lamellar Polymer Crystal Studied by Dynamic Monte Carlo Simulations

“…To be more precise, one lamellar crystallite usually contains different sectors, and they are distinguished by a difference in the average orientation of regular chain folding, which is parallel to the smooth growth front. 8 Evidence for such sectorization comes from several experiments, most notably paraffin decoration techniques. 9 Recent developments in computer simulations have made it possible to observe polymer crystal growth at a molecular level.…”

Spherulitic Growth in Crystalline Polymers

“…There have been suggestions based on the tilting of crystalline stems with respect to the folding surfaces; by tilting, folded chains can relax the congestion among them by providing larger cross-sectional surface area per stems ( Fig. 4b) (Bassett et al 1959;Reneker and Geil 1960). Firstly, in the Keith-Padden model (Fig.…”