Microstructural Change of Poly(1-butene) during Crystallization, Phase Transition, and Melting Revealed by Synchrotron Small-Angle X-ray Scattering

Abstract

For a long time, polymer lamellar crystals were hard to characterize accurately and comprehensively. The main reason is that the small-angle X-ray scattering (SAXS) mechanism of semicrystalline polymers has not been elucidated thoroughly. In recent years, we examined SAXS in semicrystalline polymers carefully, finding that SAXS in semicrystalline polymers probably is from a new physical mechanism, that is, evanescent wave-induced scattering. Based on the finding, a full set of new characterization methodologies for lamellar stack were proposed. In this study, to help more researchers to understand the new theory and methodologies, we introduce our new theory and methodologies systematically, with poly­(1-butene) as an example. Results indicate that the new methods can extract effectively the structural information during the isothermal crystallization, phase transition, and melting of poly­(1-butene), i.e., the lamellar thickness, long period, and lateral size. With the methods, it was found that the lamellar crystal as a whole can contract by 20% ± 4.5% in the lateral size and elongate by 12% along the chain direction during the phase transition, in agreement with the theoretical prediction. This conversely indicates the validation of the new theory. Initial evidence for the existence of the evanescent wave was also given. It is expected that, with this study, more researchers can better employ synchrotron SAXS to study polymer crystallization issues.

The melt memory effects in polymer crystallization

“…New development in data analysis can potentially introduce new findings with X‐ray data. Li et al 51 recently proposed new methodologies to interpret SAXS data from polymers crystallization based on evanescent wave‐induced scattering, so that the long period, lamellar thickness, and lateral size can be calculated more accurately. It was found that the lamellar size shrunk by 20% in lateral size and expand by 12% along the stem during phase transition of poly(1‐butene) form II to form I.…”

The influence of melt status and beta-nucleation agent distribution on the crystallization of isotactic polypropylene

“…To observe the structural change from SAXS more clearly, SAXS was corrected with a new method proposed by us recently. [60][61][62][63] SAXS was first subtracted by free-melt scattering and then multiplied by q 4 . The aim of subtracting free-melt scattering is to remove other minor scatterings such as air scattering, scattering induced directly by incident X-ray.…”

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.…”