Kou Ran, Zhang Jian, Chen Zhen, Liu Guangming
Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei, 230026, P. R. China.
Chemphyschem. 2018 Jun 5;19(11):1404-1413. doi: 10.1002/cphc.201701256. Epub 2018 Apr 17.
We demonstrate here that the properties of poly (2-(methacryloyloxy) ethyl trimethylammonium chloride) brushes can be tuned by counterion species. When the brushes are exposed to external chloride (Cl ) counterions, obvious dehydration and collapse are only observed at high salt concentrations. In the presence of very strongly chaotropic perchlorate (ClO ), the brushes strongly dehydrate and collapse at a very low salt concentration. For the strongly chaotropic thiocyanate ion (SCN ), the changes in hydration and conformation of the brushes are similar to those observed for ClO but at a smaller extent at very low salt concentrations. With the addition of kosmotropic acetate (Ac ), hydration of the brushes increases, accompanied by a swelling of the brushes in the low-salt-concentration regime. In contrast, the brushes dehydrate and collapse with increasing concentration of Ac in the high-salt-concentration regime. The counterion specificity of the brushes demonstrated here is determined by specific ion-pairing interactions through modulating the osmotic pressure within the brushes and the hydrophobicity of the ion pairs.
我们在此证明，聚（2-（甲基丙烯酰氧基）乙基三甲基氯化铵）刷的性质可通过抗衡离子种类进行调节。当刷暴露于外部氯离子（Cl⁻）时，仅在高盐浓度下才观察到明显的脱水和塌陷。在存在极强离液序列高氯酸根（ClO₄⁻）的情况下，刷在非常低的盐浓度下就会强烈脱水并塌陷。对于强离液序列硫氰酸根离子（SCN⁻），刷的水合作用和构象变化与ClO₄⁻的情况相似，但在非常低的盐浓度下程度较小。随着促水合乙酸根（Ac⁻）的加入，刷的水合作用增加，同时在低盐浓度范围内刷会膨胀。相反，在高盐浓度范围内，随着Ac⁻浓度的增加，刷会脱水并塌陷。此处所展示的刷的抗衡离子特异性是通过调节刷内的渗透压和离子对的疏水性，由特定的离子对相互作用决定的。
