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

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• 作者：Luis A. Bastardo ; Joseph Iruthayaraj ; Maria Lundin ; Andra Dedinaite ; Auš ; vydas Vareikis ; Rič ; ardas Makuš ; ka ; Albert van der Wal ; Istvá ; n Furó ; Vasil M. Garamus ; Per M. Claesso
• 关键词：Comb polymer ; Comb polyelectrolyte ; Polymer– ; surfactant association ; Polyelectrolyte– ; surfactant aggregate ; Small-angle neutron scattering ; Light scattering ; NMR ; Surface tension ; Polyelectrolyte ; Surfactant ; SDS
• 刊名：Journal of Colloid and Interface Science
• 出版年：2007
• 出版时间：1 August 2007
• 年：2007
• 卷：312
• 期：1
• 页码：21-33
• 全文大小：385 K

文摘

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 PEO₄₅MEMA: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 PEO₄₅MEMA: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.