Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR

• Published in: Journal of colloid and interface science Vol. 312; no. 1; pp. 21 - 33
• Main Authors: Bastardo, Luis A., Iruthayaraj, Joseph, Lundin, Maria, Dedinaite, Andra, Vareikis, Aušvydas, Makuška, Ričardas, van der Wal, Albert, Furó, István, Garamus, Vasil M., Claesson, Per M.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.08.2007; Elsevier
• Subjects: Chemistry; Colloidal state and disperse state; Comb polyelectrolyte; Comb polymer; Exact sciences and technology; Fysikalisk kemi; General and physical chemistry; Kemi; Light scattering; NATURAL SCIENCES; NATURVETENSKAP; NMR; Physical chemistry; Polyelectrolyte; Polyelectrolyte–surfactant aggregate; Polymer–surfactant association; SDS; Small-angle neutron scattering; Surface and colloid chemistry; Surface physical chemistry; Surface tension; Surfactant; Yt- och kolloidkemi; Polyelectrolyte; Polyelectrolyte–surfactant aggregate; NMR; Small-angle neutron scattering; SDS; Polymer–surfactant association; Light scattering; Comb polyelectrolyte; Surface tension; Comb polymer; Surfactant; Surfactant polymer; Polymer; NMR spectrometry; Complexes; Lauryl sulfate; Polymer-surfactant association; Polyelectrolyte-surfactant aggregate; Charge density; Association; Small angle neutron scattering; Aggregate; Physicochemical properties; polymer-surfactant association; polyelectrolyte-surfactant aggregate; polyelectrolyte; comb polymer; small-angle neutron scattering; light scattering; surface tension; comb polyelectrolyte; surfactant
• ISSN: 0021-9797; 1095-7103; 1095-7103
• DOI: 10.1016/j.jcis.2006.09.004

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 45MEMA: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 Å. 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 45MEMA: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. Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR.