Dissociation Behavior of Weak Polyelectrolyte Brushes on a Planar Surface
Dissociation Behavior of Weak Polyelectrolyte Brushes on a Planar Surface
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DOI：
10.1021/la8039384
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发表时间：
2009-04-21
期刊：
影响因子：
3.9
通讯作者：
Ober, Christopher K.
中科院分区：
文献类型：
--
作者：
Dong, Rong;Lindau, Manfred;Ober, Christopher K.
采用表面引发原子转移自由基聚合法，在水介质中合成了聚丙烯酸（PAA）刷和聚甲基丙烯酸（PMAA）刷。采用傅里叶变换红外光谱（FTIR）滴定法和接触角滴定法研究了这两种刷的解离行为。而FTIR滴定给出了多酸刷的有效体积pK（a）值（PAA刷的pK（a）（体积）为6.5-6.6，PMAA刷的pK（a）（体积）为6.9-7.0），接触角滴定提供了刷的有效表面pK（a）（PAA刷的pK（a）（sruf）为4.4 +/- 0.01，PMAA刷的pK（a）（surf）类似于4.6 +/-0.01）。0.1）。pK（a）（本体）和pK（a）（表面）之间的差异表明，离基材表面较远的酸基团更容易水解，并且具有较小的pK（a）值。虽然这种行为的弱磁刷已预测的理论模拟，在这里，我们提供了第一个实验证据，这种行为。
Poly(acrylic acid) (PAA) brushes and poly(methacrylic acid) (PMAA) brushes on gold substrates were synthesized by surface-initiated atom-transfer radical polymerization of sodium acrylate and sodium methacrylate in water media at room temperature. Fourier transform infrared spectroscopy (FTIR) titration and contact angle titration methods were used in combination to investigate the dissociation behavior of these two brushes. Whereas FTIR titration gives effective bulk pK(a) values of the polyacid brushes (pK(a)(bulk) of PAA brushes is 6.5-6.6 and pK(a)(bulk) of PMAA brushes is 6.9-7.0), contact angle titration provides effective surface pK(a) of the brushes (pK(a)(sruf) of PAA brushes is 4.4 +/- 0.01 and pK(a)(surf) of PMAA brushes is similar to 4.6 +/- 0.1). The difference between pK(a)(bulk) and pK(a)(surf) suggests that acid groups further from the substrate surface are easier to ionize and have smaller pK(a) values. Although such behavior of weak polyelectrolyte brushes has been predicted by theoretical simulation, here we provide the first experimental evidence of this behavior.