Aggregation behavior of tyloxapol, a nonionic surfactant oligomer, in aqueous solution

Oren Regev, Raoul Zana

Research output: Contribution to journalArticlepeer-review

87 Scopus citations

Abstract

The aggregation behavior of Tyloxapol, a nonionic surfactant oligomer with a repeating unit close to Triton X-100 (TX100), and a maximum degree of polymerization of about 7, has been investigated in aqueous solution by means of fluorescence probing, time-resolved fluorescence quenching (TRFQ) and transmission electron microscopy at cryogenic temperature (cryo-TEM). The plot of the pyrene fluorescence intensity ratio I1/I3 against the Tyloxapol concentration shows no clear evidence of a critical micelle concentration contrary to TX100. Nevertheless, the fitting of these data, assuming a partition of pyrene between Tyloxapol aggregates and water, yields cmc values in the micromolar range, i.e., about a hundred times lower than for the 'monomer' TX100. The values of I1/I3 at high surfactant concentrations indicate that Tyloxapol micelles provide pyrene a less polar environment than TX100 micelles. The use of the viscosity-sensitive probe 1,3-dipyrenylpropane indicates that the microviscosity of Tyloxapol micelles is quite high, three to four times larger than that for TX100 micelles, and decreases rapidly with increasing temperature. Also the microviscosities of both TX100 and Tyloxapol micelles are larger than those for the micelles of the nonionic ethoxylated surfactant C12E9. The aggregation numbers of Tyloxapol and of TX100 micelles measured using TRFQ increase with temperature, with the Tyloxapol micelles being smaller than the TX100 micelles. Cryo-TEM shows that the Tyloxapol micelles remain spheroidal up to a concentration of about 10 wt%. At 15 wt%, some regions of ordered elongated micelles are also observed which may be the precursors of the hexagonal phase known to occur at about 35 wt%.

Original languageEnglish
Pages (from-to)8-17
Number of pages10
JournalJournal of Colloid and Interface Science
Volume210
Issue number1
DOIs
StatePublished - 1 Feb 1999

Keywords

  • Aggregation in aqueous solution
  • Cmc
  • Micelle microviscosity
  • Micelle shape
  • Nonionic surfactant oligomer
  • Triton X-100
  • Tyloxapol

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry

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