Supermolecular structure of poly(ethylene oxide) fractions

Abstract

SynopsisThe crystalline morphology, or supermolecular structure, of poly(ethy1ene oxide) has been studied as a function of molecular weight and crystallization conditions. Molecular weight fractions, covering the range 6 X 103 to 1 X lo7 are used over the range of accessible temperatures for isothermal crystallization as well as for a large set of controlled nonisothermal crystallization conditions. A morphological map is constructed from these studies and compared with the literature results. Prior reports were primarily confined to low molecular weights, which restricted the generalization of the findings. In the present work, as a consequence of the extended molecular weight range, conditions are established for the systematic development of several different, well-defined, organized supermolecular structures as well as for highly crystalline but disorganized systems. Strong similarities are found between the results for poly(ethy1ene oxide) and previous reports for linear polyethylene. A generalization for all chain molecules is suggested.

Annealing in Low Density Polyethylene at Several Temperatures

“…The resulting T 0 m was 139. 2 C as can be seen in Figure 2. Several annealed ethylene polymer systems also show a linear plot of the melting temperature of the crystal fraction generated at the annealing temperature against the annealing temperature as, for instance, high density polyethylene (HDPE) 20 and ethylene-hexene copolymer.…”

“…Therefore, only one endotherm appears above 105 C. At 115 C all crystals of the original distribution melt and the sharp endotherm centred at 117. 2 C reflects the melting of the crystals generated at T a .…”

“…[1][2][3] For several polymers the analysis encompass a temperature range large enough to detect the so-called nucleation/reptation transition. 4 As the temperature decreases from the melting condition, the lamellar growth rate, G, increases.…”

“…For amorphous and crystalline phases rearrangements, the importance of annealing is that such experiments can detect the partial melting followed by recrystallization [13][14][15] as well as the phenomenum of isothermal thickenning. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The evident difference between the isothermal crystallization and the annealing experiment is the initial state of the processes. In the former case the system is almost totally amorphous at the beginning, whereas in the latter the crystallization starts from a semicrystalline condition.…”

Imaging of Melting and Crystallization of Poly(ethylene oxide) in Real-Time by Hot-Stage Atomic Force Microscopy

“…27 PEO was chosen for this study because of it's low melting point (T m°) 69°C) and because it has been shown to exhibit a wealth of morphological forms. [28][29][30] …”