Molecular segregation and nucleation of poly(ethylene oxide) crystallized from the melt. III. Morphological study

Abstract

Solvent extraction followed by DSC, optical microscopy, and transmission electron microscopy show morphological evidence of molecular segregation for binary mixtures of poly(ethylene oxide)s (PEO). Two segregation types, namely microscopic and macroscopic segregation, have been found. A special etching method for PEO has been developed, and the crystalline textures of bulk samples crystallized at different temperatures for different molecular‐mass mixtures are reported. A linkage between optical and electron microscopy is suggested. The morphology of PEO binary mixtures is crystallization‐temperature and molecular‐mass dependent.

Free‐volume and crystallinity in low molecular weight poly(ethylene oxide)

“…The qualitative analysis of PLOM PEO1000 images indicates the formation of spherulites larger than 1 mm and the loss of the regular Maltese cross. Similar observations were also reported for PEO mixtures by Cheng et al39 The low molecular mass fraction of the mixture crystallizes later, depending on the crystallization temperature. The open texture of PEO1000 spherulite changes to a compact one for all other samples.…”

Hydrogen Bond Induces Hierarchical Self‐Assembly in Liquid‐Crystalline Block Copolymers

“…As a result, both the MPS nanoconfinement effect and the hydrogen bonding between PEO and the urethane group should greatly influence the PEO crystallization. In general, the PEO crystallizes with folded polymer chain, and amorphous PEO stays in chaos with entangled polymer chains . Driven by the competition between the crystallization and the restriction effect, MPS process occurs in a much subtler scale, leading to the formation of lamellar structures (about 4 nm) inner the PEO nanocylinders with the crystallized PEO inserting in the amorphous PEO domains at the existence of hydrogen bonding interactions, as shown in Scheme .…”

The preparation of ultra narrow molecular weight distribution poly(ethylene glycol)s by fractional crystallization from solution

“…The earliest studies for the fractionation of high molecular weight PEGs from methyl ethyl ketone, xylene, and benzene/isooctane solution mixture have been achieved by Booth and Price11 and Beech and Booth 12. However, only a few articles have been reported for fractionation from solution mixtures as a method for evaluation of very narrow molecular weight distribution, low molecular weight PEG fractions 13–15. In the present work, optimum fractional crystallization conditions for the preparation of very narrow molecular weight distribution low molecular weight PEGs from n ‐butanol/ n ‐heptane solution mixtures have been determined.…”