Raman longitudinal acoustic mode studies of poly(ethylene oxide) and α,ω-methoxylated poly(ethylene oxide) fractions during isothermal crystallization from the melt
✍ Scribed by Insun Kim; Samuel Krimm
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 182 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0887-6266
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✦ Synopsis
Raman longitudinal acoustic mode (LAM) spectra have been obtained during isothermal crystallization from the melt at various temperatures of a poly(ethylene oxide) (PEO) fraction of molecular weight about 3000 and an a,v-methoxylated fraction (MPEO) derived from it. For both fractions, we find that noninteger fold (NIF) chains are formed in the initial stages of crystallization. With time, and more rapidly at higher crystallization temperatures, the NIF chains transform into integer-fold (IF) structures. The final morphologies of the two fractions are similar, consisting of IF mixed-crystal lamellae composed mainly of extended (E) chains with embedded oncefolded (F2) chains. This solid-state transformation from the NIF state may proceed through the F2 state. The effect of hydrogen bonds in the case of PEO is not to change the transformation process but to slow it when compared to MPEO. Comparison with small-angle x-ray scattering (SAXS) data indicates that in both cases the NIF chains are tilted to the lamellar surface and that the tilt from perpendicular eventually disappears as IF chains form at the later stages of crystallization.