Isothermal growth, thickening, and melting of poly(ethylene oxide) single crystals in the bulk

Abstract

Characteristic features of isothermal growth, thickening, and melting behavior of melt grown single crystals of low molecular weight poly (ethylene oxide) fractions are presented and discussed in terms of their relevance to basic concepts of polymer crystal growth. Measurements of growth (G) and thickening rates of once folded chain crystals were extended (up to the melting point) into a temperature range where usually only extended chain crystals grow. Monolayer extended and folded chain crystals melt by lateral shrinkage, the rate of which (G−) depends not only on temperature, but also on thermal history. G− increases exponentially with the degree of superheating, and the value of the temperature coefficient d log G−/dT is proportional to the lamellar thickness. In the narrow temperature interval where transition from once folded to extended chain growth occurs, the crystal morphology displays some spectacular features. These may be accounted for in terms of the crystal habit and the rate of completion, g. of a molecular layer in the particular (hk0) prism face considered. Morphological analysis shows that g is of the same order of magnitude as G(hkO), leading to the conclusion that the growth of these PEO crystals is controlled by multiple surface nucleation rather than by deposition of a single surface nucleus.

Heterogeneous Distribution of Entanglements in a Nonequilibrium Polymer Melt of UHMWPE: Influence on Crystallization without and with Graphene Oxide

“…The shift to the higher temperature, with increasing the crystallization temperature, is in good agreement with the earlier findings and can be explained by the increase in crystal thickness and/or crystal perfection [25,26]. However, the appearance of high endothermic peak at 141.5 °C (independent of the annealing time and annealing temperature in melt and will be discussed later e.g.…”

Fine fibrillar and rectangular/hexagonal ordered grains of poly(3-hexyl thiophene) and poly(ethylene glycol) developed by seeding technique

“…Even though in crystallization state different morphologies are obtainable from concentrated solutions or from polymer melts, ranging from axialites, dendrites to spherulites, crystallization into somehow well-defined single crystals is delimited to supercooled dilute solutions [1]. An ample range of empirical works were dedicated to study the diffraction effects, lateral habits, lamellar structures, and crystal orientation of poly(ethylene oxide) (PEO) single crystals [1][2][3][4][5][6][7][8][9][10][11][12][13]. In a frontier step, Lin and his coworker studied semicrystalline diblock copolymer platelets of PEO-bpolystyrene (PS) in dilute solution by means of small-angle neutron scattering (SANS) [14].…”

A Review on Polymer Crystallization Theories

“…An integer folded phenomenon can usually be observed in the crystallization of n-alkanes [95] and low molecular weight PEO [96][97][98], which is probably because integer fold can exclude all end defects out of bulk crystals, and thereby reduce the free energy. In a certain temperature range, two adjacent growth modes, for instance, an extended chain and a once-folded chain, can coexist, since they have approximately the same growth rate.…”