Influence of molecular structure on the ideality of mixing in micelles formed in binary mixtures of surface-active drugs

Pablo Taboada, David Attwood, Juan M. Ruso, Manuel García, Félix Sarmiento, Victor Mosquera

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The influence of the structure of the hydrophobic group on the ideality of mixing in binary mixtures of surface active molecules has been investigated using combinations of amphiphilic penicillins. Critical concentrations (cc) of the binary mixtures of these anionic surfactants were determined by conductivity measurements as a function of the composition. The nonideality of mixing was evaluated using a regular solution approximation and expressed in terms of the interaction parameter, β. Mixing in micelles formed in binary mixtures of the structurally similar penicillins cloxacillin, dicloxacillin, and flucloxacillin was ideal (β = 0). In contrast, the combination of either cloxacillin or dicloxacillin with the penicillin nafcillin produced mixed micelles in which the mixing deviated from ideality (β = +0.1 to +0.2). The positive values of β for these systems indicated negative synergism between components of the mixtures that may be a consequence of the marked structural differences between the hydrophobic groups of these drugs. The composition of the mixed micelles was derived from the cc data by application of a theoretical treatment based on excess thermodynamic quantities.
    Original languageEnglish
    Pages (from-to)270-275
    Number of pages5
    JournalJournal of Colloid and Interface Science
    Volume216
    Issue number2
    DOIs
    Publication statusPublished - 15 Aug 1999

    Keywords

    • Amphiphilic penicillins
    • Critical micelle concentrations
    • Mixed micelles

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