Hydration in Weak Polyelectrolyte Brushes
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- 作者：Chaitra Deodhar ; Erick Soto-Cantu ; David Uhrig ; Peter Bonnesen ; Bradley S. Lokitz ; John F. Ankner ; S. Michael Kilbey ; II
- 刊名：ACS Macro Letters
- 出版年：2013
- 出版时间：May 21, 2013
- 年：2013
- 卷：2
- 期：5
- 页码：398-402
- 全文大小：269K
- 年卷期：v.2,no.5(May 21, 2013)
- ISSN：2161-1653
文摘
Weak polyelectrolytes (PEs) are complex because intertwined connections between conformation and charge are regulated by the local dielectric environment. While end-tethered PE chains鈥攕o-called PE 鈥渂rushes鈥濃€攁re archetypal systems for comprehending structure鈥損roperty relationships, it is revealed that the reference state nominally referred to as 鈥渄ry鈥?is, in fact, a situation in which the chains are hydrated by water vapor in the ambient. Using charge-negative PE homopolymer brushes based on methacrylic acid and copolymer brushes that incorporate methacrylic acid and 2-hydroxyethylmethacrylate, we determine self-consistently the water content of PE films using neutron reflectometry under different hydration conditions. Modeling multiple data sets, we obtain dry polymer mass density and layer thickness, independent of adsorbed water, and PE brush profiles into different pH solutions. We show that hydration of the chains distorts, here by as much as 30%, the quantification of these important physical parameters benchmarked to films in ambient conditions.