Sanjuan S, Perrin P, Pantoustier N, Tran Y
Laboratoire de Physico-chimie des Polymères et des Milieux Dispersés, ESPCI, CNRS, UPMC, 10 rue Vauquelin, 75231 Paris Cedex 05, France.
Langmuir. 2007 May 8;23(10):5769-78. doi: 10.1021/la063450z. Epub 2007 Apr 11.
We synthesize polybase brushes and investigate their swelling behavior. Poly(2-(dimethylamino)ethyl methacrylate)) (PDMAEMA) brushes are prepared by the "grafting from" method using surface-initiated Atom Transfer Radical Polymerization to obtain dense brushes with relatively monodisperse chains (PDI = 1.35). In situ quaternization reaction can be performed to obtain poly(2-(trimethylamino)ethyl methacrylate)) (PTMAEMA) brushes. We determine the swollen thickness of the brushes using ellipsometry and neutron reflectivity techniques. Brushes are submitted to different solvent conditions to be investigated as neutral brushes and weak and strong polyelectrolyte brushes. The swelling of the brushes is systematically compared to scaling models. It should be pointed out that the scaling analysis of different types of brushes (neutral polymer and weak and strong polyelectrolyte brushes) is performed with identical samples. The scaling behavior of the PDMAEMA brush in methanol and the PTMAEMA brush in water is in good agreement with the predicted scaling laws for a neutral polymer brush in a good solvent and a polyelectrolyte brush in the osmotic regime. The salt-induced contraction of the quaternized brush is observed for high salt concentration, in agreement with the predicted transition between the regimes of the osmotic brush and the salted brush. From the crossover concentration, we calculate the effective charge ratio of the brush following the Manning counterion condensation. We also use PDMAEMA brushes as pH-responsive polybase brushes. The swelling behavior of the polybase brush is intermediate with respect to the behavior of the neutral polymer brush in a good solvent and the behavior of the quenched polyelectrolyte brush, as expected. The effective charge ratio of the PDMAEMA brush is determined as a function of pH using the scaling law of the polyelectrolyte brush in the osmotic regime.
我们合成了聚碱刷并研究了它们的溶胀行为。通过使用表面引发的原子转移自由基聚合的“接枝自”方法制备聚（甲基丙烯酸 2-（二甲氨基）乙酯）（PDMAEMA）刷，以获得具有相对单分散链（PDI = 1.35）的致密刷。可以进行原位季铵化反应以获得聚（甲基丙烯酸 2-（三甲基氨基）乙酯）（PTMAEMA）刷。我们使用椭偏仪和中子反射率技术确定刷的溶胀厚度。将刷置于不同的溶剂条件下，作为中性刷、弱聚电解质刷和强聚电解质刷进行研究。将刷的溶胀与标度模型进行系统比较。应该指出的是，对不同类型的刷（中性聚合物刷以及弱聚电解质刷和强聚电解质刷）的标度分析是使用相同的样品进行的。PDMAEMA 刷在甲醇中的标度行为以及 PTMAEMA 刷在水中的标度行为与在良溶剂中的中性聚合物刷和在渗透 regime 中的聚电解质刷的预测标度定律高度吻合。在高盐浓度下观察到季铵化刷的盐诱导收缩，这与渗透刷和盐化刷 regime 之间的预测转变一致。从交叉浓度，我们根据曼宁反离子凝聚计算刷的有效电荷比。我们还使用 PDMAEMA 刷作为 pH 响应性聚碱刷。正如预期的那样，聚碱刷的溶胀行为在良溶剂中的中性聚合物刷的行为和淬灭聚电解质刷的行为之间处于中间状态。使用渗透 regime 中聚电解质刷的标度定律确定 PDMAEMA 刷的有效电荷比作为 pH 的函数。
