A New Scenario of Shish-Kebab Formation from Homogeneous Solutions of Entangled Polymers: Visualization of Structure Evolution along the Fiber Spinning Line

Abstract

Self-assembly of ordered structures under the external fields is one of the most important and fundamental research themes in physical science of soft matters including polymers. The “shish-kebab” self-assembly is a most intriguing but fundamental crystalline superstructure formed in polymers under various flow fields. Nevertheless the mechanism of shish-kebab formation is not fully understood yet. In order to clarify the mechanisms for polymer solutions, we have investigated the flow-induced self-assembling structures evolved along a fiber spinning line for concentrated polymer solutions and proposed a new scenario of the kinetic pathway leading to shish-kebab formation and various transient structures evolved therein. The proposed pathway comprises two stages: (i) the early stage pathway before an onset of the birefringence upturn, where the flow-induced phase separation plays a dominant role on creating a series of various transient structures leading to the “sring-like structure” (denoted as “string”), all of which are hardly able to be detected by conventional SAXS, SANS, and WAXD; (ii) the late stage pathway after the onset of the birefringence upturn where the flow-induced crystallization plays a dominant role on generating bundles of stretched chains, probably via the so-called coil–stretched chain transition, within the strings grown in the early stage pathway, followed by nucleation–growth of shishs and epitaxial crystallization of kebab lamellae onto shishs from the random coils incorporated within the demixed domains which coexist with shishs within the given string. Our work therefore elucidates an important role of the flow-induced phase separation on the flow-induced shish-kebab formation.

High‐Strain Shape Memory Behavior of PLA–PEG Multiblock Copolymers and Its Microstructural Origin

“…At this point, it is sensible to conclude that the negative form birefringence component emerging after recovery originated from stacks of chain folded lamellar crystallites of PLA formed perpendicularly to the extended‐chain crystallites of PLA due to fibrillar‐to‐lamellar transformation, generating the so‐called shish–kebab structure. Such structure has been reportedly observed in several polymers subjected to flow field under solution or melt state as well as uniaxial hot‐stretching followed by annealing at very high temperature (in the melting temperature range) under stretched state . The unprecedented formation of shish–kebab structure at relatively low temperature under rubbery state discovered in this work presents the great technological significance, which would extend the borderline of the possibilities in designing material structure.…”

Cascading time evolution of dissipative structures leading to unique crystalline textures

“…7e) did not disappear even after the shear cessation at 124 C as shown in Fig. 7(f), the intensity of the streak-like SALS pattern further increased with t (Murase et al, 2005(Murase et al, , 2009(Murase et al, , 2011, and the solution after cooling showed the shishkebabs under TEM, as shown in Fig. 7(l).…”

Effect of processing parameters on the morphology development during extrusion of polyethylene tape: An in-line small-angle X-ray scattering (SAXS) study

“…Subsequent annealing and recrystallization of the off-line samples gave denser and shorter oriented shish-kebab structures at high stretching rates, compared with dense but longer structures at low stretching rates. Murase [25] gave a comprehensive study of the flow-induced self-assembling structures that evolve down a fibre spin-line for concentrated polymer solutions proposing a two-stage pathway for shish-kebab formation. Early stages saw the evolution of transient phases leading to string-like structures.…”