Liquid crystal phase behavior of branched poly(oxyethylene) surfactants

John M. Walsh, Gordon J T Tiddy

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The phase behavior of several novel surfactants having hydrophobic and poly(oxyethylene) (EOm) polar groups linked by a glyceryl (G) moiety has been studied using the optical microscope penetration scan. Use of the G linker gives surfactants with two EO groups attached to one hydrophobic chain, or two hydrophobic chains attached to one EO group, so that both the hydrophobic and polar groups can be considered to be "branched". Several surfactants having the general formula X-O-CH2-CH(OY)-CH2O-X, where X = alkyl chain and Y = EOm or vice versa, have been examined, mostly with oleyl chains (C18=) as the hydrophobic group(s). In addition, we also examined two conventional surfactants with oleyl hydrophobic groups to allow a proper comparison of the novel surfactants with the available literature. Generally, we find that the mesophases observed are similar to those found for conventional surfactants, with the "packing constraint" model providing a reasonable qualitative description of behavior, Also, the data suggest that the G linker is part of the hydrophobic region of the surfactant aggregates. Remarkably, one of the compounds, C18=G-di-EO6, exhibits four different regions for the small-micelle cubic phases (I1). A second surfactant, di-C18=G-EO12, shows very different mesophase sequences on heating and cooling, indicating the existence of several phases of similar stability with slow equilibration times. This slow phase equilibration is unusual for poly(oxyethylene) surfactants.
    Original languageEnglish
    Pages (from-to)5586-5594
    Number of pages8
    JournalLangmuir
    Volume19
    Issue number14
    DOIs
    Publication statusPublished - 8 Jul 2003

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