Mechanism of the pH-induced discontinuous swelling/deswelling transitions of poly(allylamine hydrochloride)-containing polyelectrolyte multilayer films
Mechanism of the pH-induced discontinuous swelling/deswelling transitions of poly(allylamine hydrochloride)-containing polyelectrolyte multilayer films
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DOI：
10.1021/ma047667g
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发表时间：
2005-04-19
期刊：
影响因子：
5.5
通讯作者：
Rubner, MF
中科院分区：
文献类型：
--
作者：
Itano, K;Choi, JY;Rubner, MF
用FT-IR光谱、原位原子力显微镜(AFM)和原位椭圆偏振光谱仪研究了含有聚烯丙基胺盐酸盐(PAH)的聚电解质多层膜的不连续溶胀/脱胀转变的机理。研究发现，组装pH在决定多层膜组装后的pH依赖溶胀行为中起着关键作用。在pH为8.5的条件下组装的多层膜在pH为2.0-10.5的范围内表现出不依赖于pH的溶胀行为，而当组装pH大于8.5时，呈现出显著的不连续溶胀转变。用FT-IR光谱明确地证明了在高pH(>；8.5)条件下组装的多环芳烃/磺化聚苯乙烯(SPS)多层膜的pH触发的不连续溶胀/脱水转变是由多环芳烃在多层膜组装过程中形成的游离胺基电离度的变化所驱动的。这些溶胀/脱水转变的pH触发点由疏水缔合的多环芳烃链段的消除/重建决定。这种疏水相互作用导致多环芳烃的游离胺基团的pKa移动到异常低的值(约pH 4.0)。研究发现，聚阴离子与多环芳烃组装的类型对脱水动力学有很大的影响。
The mechanism of the discontinuous swelling/deswelling transitions exhibited by polyelectrolyte multilayers containing poly(allylamine hydrochloride) (PAH) was examined by FT-IR spectroscopy, in-situ atomic force microscopy (AFM), and in-situ ellipsometry. Assembly pH was found to play a critical role in determining the postassembly pH-dependent swelling behavior of multilayers containing PAIT Multilayer films assembled at pH < 8.5 were found to exhibit pH-independent swelling behavior over the pH range of 2.0-10.5, whereas dramatic discontinuous swelling transitions were observed when the assembly pH was greater than 8.5. FT-IR spectroscopy was used to demonstrate unequivocally that the pH-triggered, discontinuous swelling/deswelling transitions of PAH/sulfonated polystyrene (SPS) multilayers assembled at high pH (> 8.5) are driven by changes in the degree of ionization of free amine groups of PAH that are established during multilayer assembly. The pH trigger points of these swelling/ deswelling transitions are determined by the elimination/reestablishment of hydrophobically associated PAH chain segments. Such hydrophobic interactions are responsible for shifting the pKa of the free amine groups of PAH to unusually low values (ca. pH 4.0). The kinetics of deswelling were found to be strongly influenced by the type of polyanion assembled with PAH.