Issue 42, 2020

Formation of well-organized, concentric-ringed spherulites of four-arm star symmetric PEO-b-PCL via confined evaporative crystallization

Abstract

Formation of well-organized, periodic spherulites of four-arm star symmetric poly(ε-caprolactone)-b-poly(ethylene oxide) (PEO-b-PCL) via confined slow evaporative crystallization of solution-cast films is reported, and the microstructures were characterized by optical microscopy, atomic force microscopy, and X-ray scattering and diffraction techniques. Having a Maltese cross pattern, the spherulites exhibit a unique concentric-ringed morphology under both polarized and unpolarized lights. The pattern regularity and ring periodicity are both controllable. The tunable periodicity is in the range of 10–45 μm, and the size of the spherulites even exceeds one millimeter. It shows that such birefringent concentric-structure is a reflection of periodic change of thickness caused by rhythmic stacking of lamellar crystals with varied orientation along the radial direction. The lamellae in valley bands are nearly flat-on, while the lamellar orientation becomes gradually inclined with normal thickening, leading to continuously enhanced birefringence in ridges. Finally, a coupling of the poor solubility of the PEO block and its inner geometry in the star topology is then presented to illustrate a possible solvent-assisted topology confined mechanism for inducing PCL-dominated rhythmic crystallization into concentric-ringed spherulites.

Graphical abstract: Formation of well-organized, concentric-ringed spherulites of four-arm star symmetric PEO-b-PCL via confined evaporative crystallization

Article information

Article type
Paper
Submitted
12 Aug 2020
Accepted
12 Sep 2020
First published
14 Sep 2020

CrystEngComm, 2020,22, 7016-7024

Formation of well-organized, concentric-ringed spherulites of four-arm star symmetric PEO-b-PCL via confined evaporative crystallization

J. Wei, L. Wu, H. Zhu, Y. Li and Z. Wang, CrystEngComm, 2020, 22, 7016 DOI: 10.1039/D0CE01183E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements