Vagharchakian Laurianne, Desbat Bernard, Hénon Sylvie
Matière et Systèmes Complexes, CNRS UMR 7057, Université Paris 7, case courrier 7056, 2 place Jussieu, 75251 Paris Cedex 05, France.
J Phys Chem B. 2006 Nov 9;110(44):22197-201. doi: 10.1021/jp055936e.
We have experimentally studied the adsorption of polyelectrolytes at oppositely charged surfaces. A weak flexible polyelectrolyte, poly(acrylic acid), was adsorbed from dilute solutions on a Langmuir film of a cationic amphiphile, dimethyldioctadecylammonium bromide. The polymer surface coverage, Gamma, at equilibrium was measured by two reflectivity techniques-ellipsometry and polarization modulated infrared reflection absorption spectroscopy (PM-IRRAS)-as a function of the surface charge density, sigma, and of the polymer ionization degree, alpha. Different adsorption regimes were evidenced. For weakly charged surfaces, sigma < sigma sat, Gamma increases with sigma and with 1/alpha, as expected for a neutralization of the surface by the adsorbed polymers. For highly charged surfaces, sigma > sigma sat, the adsorption of polyelectrolytes saturates. The mean orientation of the adsorbed chains also depends on the value of sigma: it is parallel to the surface for sigma < sigma (< sigma sat) and orthogonal to the surface for sigma > sigma. We have measured the values of sigma sat and sigma as a function of alpha and compared the results with existing theories.
我们通过实验研究了聚电解质在带相反电荷表面的吸附情况。一种弱柔性聚电解质，聚丙烯酸，从稀溶液中吸附到阳离子两亲物二甲基二十八烷基溴化铵的朗缪尔膜上。通过两种反射率技术——椭偏仪和偏振调制红外反射吸收光谱法（PM - IRRAS）——测量了平衡时聚合物的表面覆盖率Γ，它是表面电荷密度σ和聚合物电离度α的函数。证明了不同的吸附状态。对于弱带电表面，σ < σsat，Γ随σ和1/α增加，这正如吸附的聚合物中和表面电荷所预期的那样。对于高带电表面，σ > σsat，聚电解质的吸附达到饱和。吸附链的平均取向也取决于σ的值：当σ < σ（< σsat）时，它与表面平行；当σ > σ时，它与表面正交。我们测量了σsat和σ作为α的函数的值，并将结果与现有理论进行了比较。
