Salt- and pH-induced swelling of a poly(acrylic acid) brush via quartz crystal microbalance w/dissipation (QCM-D)
Salt- and pH-induced swelling of a poly(acrylic acid) brush via quartz crystal microbalance w/dissipation (QCM-D)
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DOI：
10.1039/c9sm01289c
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发表时间：
2019-10-21
期刊：
影响因子：
3.4
通讯作者：
Larson, Ronald G.
中科院分区：
文献类型：
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作者：
Hollingsworth, Nisha R.;Wilkanowicz, Sabina, I;Larson, Ronald G.
我们推断弱电离聚乙烯的溶胀/去溶胀行为在KCl浓度为0.1-1000 mM，pH = 3、7和9，接枝密度σ = 0.12-2.15链/nm（2）的情况下，使用具有耗散的石英晶体微天平（QCM-D），确认并将Wu等人的工作扩展到多个链长。pH 7和9（高于pK（a）类似于5），刷最初在低KCl离子强度下溶胀（10 mM盐）与预测的缩放H一致，类似于刷高度H的N σ C-+1/3（s）-1/3，而在低盐“渗透刷”状态下，（C-s < 10 mM盐），我们发现H类似于N σ C-+1/3（s）+0.28-0.38，其对C-s的依赖性与该区域的标度理论一致，但对σ的依赖性与标度理论强烈不一致。新的结果部分证实了标度理论，并澄清了需要改进的理论和额外的数据。
We infer the swelling/de-swelling behavior of weakly ionizable poly(acrylic acid) (PAA) brushes of 2-39 kDa molar mass in the presence of KCl concentrations from 0.1-1000 mM, pH = 3, 7, and 9, and grafting densities sigma = 0.12-2.15 chains per nm(2) using a Quartz Crystal Microbalance with Dissipation (QCM-D), confirming and extending the work of Wu et al. to multiple chain lengths. At pH 7 and 9 (above the pK(a) similar to 5), the brush initially swells at low KCl ionic strength ( 10 mM salt) agree with the predicted scaling H similar to N sigma C-+1/3(s)-1/3 of brush height H, while in the low-salt "osmotic brush" regime (C-s < 10 mM salt), we find H similar to N sigma C-+1/3(s)+0.28-0.38, whose dependence on C-s agrees with scaling theory for this regime, but the dependence on sigma strongly disagrees with it. The predicted linearity in the degree of polymerization N is confirmed. The new results partially confirm scaling theory and clarify where improved theories and additional data are needed.