ISSN:
0887-6266
Keywords:
Raman spectra
;
longitudinal acoustic mode
;
poly(ethylene oxide)
;
isothermal crystallization
;
noninteger fold
;
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
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 α,ω-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 once-folded (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. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1117-1126, 1997
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
