The II to I Phase Transition of Isotactic Poly(1-butene) Single Crystals at an Early Stage

Abstract

Regular and dendritic (i.e., composed of multiple flat-on dendritic crystals with a fixed 90° branching angle) single crystals of isotactic poly­(1-butene) (iPBu) in its form II were obtained by ultrathin film melt crystallization. Their II–I phase transition behavior was studied by atomic force microscopy (AFM) and electron diffraction techniques. Ex-situ electron diffraction studies on both the regular and dendritic single crystals reveal that the II–I phase transition leads generally to the formation of untwinned hexagonal form I iPBu crystals. In-situ AFM studies on the regular single crystal show that the II–I phase transition occurs easier at its edge facets than inside the crystal, analogous to the preferential form I nucleation at the edges of individual crystal sheet within the dendritic single crystals. It is also found that inside the regular single crystal rowlike nuclei form preferentially along [100]/[010] directions of the parent form II single crystal, which may be related to a larger shrinkage in these directions caused by densification during the II–I phase transition. These obtained results may shed more light on the II–I phase transition mechanism and kinetics of the iPBu.

Identifying a Mesomorphic Boundary Zone within Polybutene-1 Single Crystals Emerging During a Crystal–Crystal Transformation

“…They confirmed the Form II to Form I phase transformation was a two-step process including nucleation and growth by the morphological study . It thus offered deeper insights into the transformation mechanism and growth kinetics of Form I crystals. − However, due to a lack of appropriate experimental observations on the boundary zone between the two crystalline phases, the actual route taken at a nanometer level when growing Form I within Form II crystals has not yet been revealed.…”

Utilizing 3-methyl-1-butene co-units to tailor phase transition behavior in butene-1 copolymers

“…7,8,13 Thus, to effectively regulate the mechanical properties, the study of the phase transition process is attracting more and more attention. 15–25 Over the past decades, various methods have been reported to tailor the phase transition process. 15,25–46 Qiao et al systematically investigated the correlation between temperature and phase transition kinetics.…”

Proliferation and Arrangement of Poly(vinylidene fluoride) Oval γ Single Crystals Grown in Its Poly(1,4-butylene adipate) Blends

“…Polymer crystals have multilevel structures, from the basic unit cell to single lamella stacked by unit cells, which are then stacked further to form spherulites or other crystalline aggregates. − Polymer single crystals with regular and unified structures have thus been extensively investigated since they can serve as a simple and ideal model system to understand the structural and morphological development during polymer crystallization. − For instance, the single crystal structure analysis of polyethylene (PE) helps us to realize the chain folding feature in polymer crystals. − Further studies reveal the sectorization and different folding directions in different sectors of lamellar single crystals. − During the development of spherulites, bifurcation, bending, twisting, and even scrolling of single crystalline lamella can take place, giving rise to various aggregated structures. ,− For example, lamellar twisting results in ring-band spherulites with alternating bright and dark bands under polarized light microsope. ,− The ring-band spherulites have been observed for a large number of crystalline polymers. For example, α-form poly­(vinylidene fluoride) (PVDF) shows typical band structure originating from the periodical twisting of α-PVDF lamellae along the radial direction .…”