title: Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR.
abstract: A low charge density polyelectrolyte with a high graft density of 45 units long poly(ethylene oxide) side-chains has been synthesized. In this comb polymer, denoted PEO(45)MEMA:METAC-2, 2 mol% of the repeating methacrylate units in the polymer backbone carry a permanent positive charge and the remaining 98 mol% a 45 unit long PEO side-chain. Here we describe the solution conformation of this polymer and its association with an anionic surfactant, sodium dodecylsulfate, SDS. It will be shown that the polymer can be viewed as a stiff rod with a cross-section radius of gyration of 29 A. The cross section of the rod contracts with increasing temperature due to decreased solvency of the PEO side-chains. The anionic surfactant associates to a significant degree with PEO(45)MEMA:METAC-2 to form soluble complexes at all stoichiometries. A cooperative association is observed as the free SDS concentration approaches 7 mM. At saturation the number of SDS molecules associated with the polymer amounts to 10 for each PEO side-chain. Two distinct populations of associated surfactants are observed, one is suggested to be molecularly distributed over the comb polymer and the other constitutes small micellar-like structures at the periphery of the aggregate. These conclusions are reached based on results from small-angle neutron scattering, static light scattering, NMR, and surface tension measurements.
authors.affiliation: Department of Chemistry, Surface Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden. per.claesson@surfchem.kth.se
authors.forename: Luis A
authors.initials: LA
authors.lastname: Bastardo
authors.forename: Joseph
authors.initials: J
authors.lastname: Iruthayaraj
authors.forename: Maria
authors.initials: M
authors.lastname: Lundin
authors.forename: Andra
authors.initials: A
authors.lastname: Dedinaite
authors.forename: Ausvydas
authors.initials: A
authors.lastname: Vareikis
authors.forename: Ricardas
authors.initials: R
authors.lastname: Makuska
authors.forename: Albert
authors.initials: A
authors.lastname: van der Wal
authors.forename: István
authors.initials: I
authors.lastname: Furó
authors.forename: Vasil M
authors.initials: VM
authors.lastname: Garamus
authors.forename: Per M
authors.initials: PM
authors.lastname: Claesson