Synthesis, characterization and swelling behaviour of poly(methacrylic acid) brushes synthesized using atom transfer radical polymerization
Synthesis, characterization and swelling behaviour of poly(methacrylic acid) brushes synthesized using atom transfer radical polymerization
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DOI：
10.1016/j.polymer.2008.11.051
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发表时间：
2009-02
期刊：
影响因子：
4.6
通讯作者：
A. Parnell;S. Martin;Cheen C. Dang;M. Geoghegan;Richard A. L. Jones;Colin J. Crook;J. Howse;A. Ryan
中科院分区：
文献类型：
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作者：
A. Parnell;S. Martin;Cheen C. Dang;M. Geoghegan;Richard A. L. Jones;Colin J. Crook;J. Howse;A. Ryan
聚（甲基丙烯酸）刷已制备利用“接枝自”技术和活性自由基合成路线，使用两个阶段的过程。首先用原子转移自由基聚合法合成了聚甲基丙烯酸1-乙氧基乙酯刷，然后热分解得到聚甲基丙烯酸。利用原子力显微镜研究了弱聚酸刷的溶胀行为随溶液pH值和盐浓度的变化。使用拉力测量来确定分子量和接枝链密度。溶胀转变被认为是在pH 9，这是显着不同的pKa（5.5）的未栓系的聚（甲基丙烯酸）。我们将pKata的这种大的变化归因于这些刷子的高接枝密度。这可以解释为相邻电荷的库仑排斥的结果。高盐浓度（0.3M Na+）也会使刷状层塌陷。相反，低盐浓度导致刷子厚度增加，这是渗透性刷子的预期行为。
Poly(methacrylic acid) brushes have been prepared utilizing the “grafting from” technique and a living radical synthesis route using a two stage process. Firstly a poly(1-ethoxyethyl methacrylate) brush was synthesized by atom transfer radical polymerization and then thermally decomposed to poly(methacrylic acid). The swelling behaviour of the weak polyacid brush was investigated as a function of pH and salt concentration in aqueous solutions using atomic force microscopy. Force pulling measurements were used to establish the molecular weight and the grafted chain density. The swelling transition was found to be at pH 9; which is significantly different to the pKa(5.5) of untethered poly(methacrylic acid). We attribute this large shift in pKato the high grafting density of these brushes. This can be explained as a result of the Coulombic repulsion of neighbouring charges. High salt concentrations (0.3M Na+) also collapse the brush layer. Conversely low salt concentrations cause an increase in the thickness of the brush, a behaviour expected for osmotic brushes.