Bastardo Luis A, Iruthayaraj Joseph, Lundin Maria, Dedinaite Andra, Vareikis Ausvydas, Makuska Ricardas, van der Wal Albert, Furó István, Garamus Vasil M, Claesson Per M
Department of Chemistry, Surface Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
J Colloid Interface Sci. 2007 Aug 1;312(1):21-33. doi: 10.1016/j.jcis.2006.09.004. Epub 2006 Sep 12.
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.
已合成了一种具有高接枝密度的低电荷密度聚电解质，其聚环氧乙烷侧链长度为45个单元。在这种梳状聚合物（记为PEO(45)MEMA:METAC-2）中，聚合物主链中2摩尔%的重复甲基丙烯酸酯单元带有永久正电荷，其余98摩尔%带有长度为45个单元的聚环氧乙烷侧链。在此，我们描述了这种聚合物的溶液构象及其与阴离子表面活性剂十二烷基硫酸钠（SDS）的缔合情况。结果表明，该聚合物可被视为一根刚性棒，其回转半径横截面为29 Å。由于聚环氧乙烷侧链的溶剂化能力下降，棒的横截面随温度升高而收缩。阴离子表面活性剂在所有化学计量比下都与PEO(45)MEMA:METAC-2有显著缔合，形成可溶性复合物。当游离SDS浓度接近7 mM时，观察到协同缔合。在饱和状态下，与聚合物缔合的SDS分子数量为每个聚环氧乙烷侧链10个。观察到两种不同的缔合表面活性剂群体，一种被认为是分子分散在梳状聚合物上，另一种在聚集体外围构成小的类似胶束的结构。这些结论是基于小角中子散射、静态光散射、核磁共振和表面张力测量结果得出的。
