title: Soluble aggregates in aqueous solutions of polyion-surfactant ion complex salts and a nonionic surfactant.
abstract: Water-soluble aggregates based on two polyion-surfactant ion "complex salts", consisting of hexadecyltrimethylammonium (C16TA(+)) and polyacrylate (PA(-)) with either 25 or 6000 repeating units, with added nonionic surfactant octaethylene glycol monododecyl ether (C12E8) have been investigated. A previous phase study has shown that added C12E5 or C12E8 can solubilize complex salts in aqueous systems, and that increasing the poly(ethylene oxide) chain length of the nonionic surfactant and/or decreasing the polyion length favors dissolution. In this work we report on dynamic light scattering, NMR diffusometry, small-angle X-ray scattering, and isothermal titration calorimetry measurements performed to characterize the solubilized composite aggregates in dilute aqueous solution in terms of size and stoichiometry. It was found that mixed aggregates of polyacrylate, C16TA(+) ions, and C12E8, with almost constant stoichiometry, coexist with free micelles of C12E8 at all investigated mixing ratios. The length of the polyion only weakly affects the stoichiometry of the mixed aggregates while strongly affecting their size and water solubility.
authors.affiliation: Division of Physical Chemistry, Department of Chemistry, Center for Chemistry and Chemical Engineering, Lund University , P.O. Box 124, SE-221 00 Lund, Sweden.
authors.forename: John
authors.initials: J
authors.lastname: Janiak
authors.forename: Matija
authors.initials: M
authors.lastname: Tomšič
authors.forename: Dan
authors.initials: D
authors.lastname: Lundberg
authors.forename: Gerd
authors.initials: G
authors.lastname: Olofsson
authors.forename: Lennart
authors.initials: L
authors.lastname: Piculell
authors.forename: Karin
authors.initials: K
authors.lastname: Schillén
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D002593:Cetrimonium Compounds / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D012492:Salts / Q000737:chemistry; D012995:Solubility; D012996:Solutions; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D002593:Cetrimonium Compounds; D007477:Ions; D012492:Salts; D012996:Solutions; D013501:Surface-Active Agents; D014867:Water; C006903:carbopol 940