Raman spectroscopic studies of poly(oxyethylene) chain conformations in non-ionic surfactants
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Raman spectra of polydisperse alkylphenolpoly(oxyethylene) surfactants have provided evidence for two dominant conformations, viz. a helical or coil conformation, common to all poly(oxyethylene) materials, and a zig-zag conformation associated with the presence of the phenol aromatic ring. Band shape analyses support a liquid-structure model based on ordered conformations existing in crystallite zones. The zig-zag conformation appears to decrease in proportion with increasing addition of H2O until a plateau is attained at > 33% H2O content. This decrease is expected to be associated with chain hydration. Gel formation at ca. 50% H2O is accompanied by a sharp peak in depolarization ratios of the zig-zag band at 802 cm–1 over the concentration interval 45–55% H2O, which has been interpreted in terms of laser polarization scrambling by randomly oriented, but internally ordered crystallite zones. Evidence is found for conformation equilibria in low-temperature (77 K) and elevated-temperature (370 K) studies of surfactants.