Ring‐banded spherulites in poly(ϵ‐caprolactone) blended with hydroxyethyl cellulose acetate as an indication for partial miscibility

Abstract

ABSTRACT:The morphologies of poly(⑀-caprolactone) (PCL) blends with hydroxyethyl cellulose acetate (HECA), a thermotropic liquid crystalline polymer (TLCP), were investigated by optical microscopy. It is demonstrated that when the pure PCL is crystallized from the melt, a spherulitic morphology arises with distinct Maltese crosses. With the addition of the HECA, the spherulites of the PCL/HECA blends show not only the Maltese crosses but also distinct extinction rings (i.e., a ring-banded spherulitic morphology). The average periodic distance of the extinction rings decreases drastically with the increase of the HECA content from 0.5 to 5 wt % in the mixture, whereas it decreases only slightly with the further increase of HECA. The periodicity of extinction rings is also influenced by the crystallization temperature. The formation of the ring-banded spherulites of PCL in PCL/HECA blends is explained in terms of stress-induced twisted lamellar crystallization and used as an indication of the molecular solubility of the HECA in the PCL.

Morphology and interference color in spherulite of poly(trimethylene terephthalate) copolyester with bulky linking pendent group

“…Band spacing is one of the basic elements of banded spherulites, and has attracted much research interest. [36][37][38][39] In our study, we find that the band spacings do increase with the increase of crystallization temperature, and vice versa (Fig. 4).…”

Morphologies and deformation behavior of poly(vinylidene fluoride)/poly(butylene succinate) blends with variety of blend ratios and under different preparation conditions

“…The increase of band periodicity with temperature is expected as frequently reported in many other polymer systems with extinction feature. [35][36][37][38] However, the increase of band periodicity with increase of the second component is quite different from the results of other blend systems, where a reduction in band spacing is usually obtained, 39,40 although with a few exceptions. 32,41 Considering that the band periodicity depends generally on the chain mobility, crystal growth rate and surface free energy, 37 the much lower melting point of PBS and its full miscibility with PVDF leads to the PBS acting as solvent for PVDF.…”

Concentric ring-banded spherulites of six-arm star-shaped poly(ε-caprolactone) via subcritical CO2

“…1a, the ringbanded spherulites with a pattern of extinction rings can be clearly observed when the sample crystallized under CO 2 , and the central crystal is much bigger than that in classical ringbanded spherulites. 7,15 The distance between crystal centers is 191.12 mm measured by Image-Pro Plus soware. While under air at ambient pressure, the typical spherulites with Maltesecross is detected (Fig.…”