Isothermal growth, thickening, and melting of polyethylene oxide) single crystals in the bulk. II

Abstract

Characteristic features of isothermal growth, thickening, and melting of melt‐grown single crystals of poly(ethylene oxide) fractions, as reported in a recent paper, are complemented and further discussed. A newly discovered phenomenon–isothermal superheating–is described and its implications are discussed. Growth and thickening rate data are analyzed in terms of the two independent molecular parameters which determine the lamellar thickness: the number, n, of folds per molecule and the total chain length, λ Current formulations of kinetic theories are critically analyzed in view of their applicability to the present growth rate data. The analysis reveals that, for the low‐molecular‐weight fractions, the theory only applies to fast growth obtained at high undercooling. At low undercooling, where molecules deposit in extended or n‐times folded‐chain conformation, however, growth proceeds by a nucleation mechanism which appears to be quite different from that implied by the theory.

Isothermal crystallization of polyethylene oxide/silver nanoplate composites

“…In Table II, σσ e = 523 ergs 2 /cm 4 in neat PEO. This is within 15% of the value reported by Kovacs et al (450 ergs 2 /cm 4 in the assumption of regime II) 39. The slight difference is presumably due to the different molecular weight of PEO ( M w = 150 k) and different expression of β in eq.…”

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.…”