Oscillatory dynamics induced in a responsive gel by a non-oscillatory chemical reaction: experimental evidence
Oscillatory dynamics induced in a responsive gel by a non-oscillatory chemical reaction: experimental evidence
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DOI：
10.1039/c1sm05226h
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发表时间：
2011-01-01
期刊：
影响因子：
3.4
通讯作者：
De Kepper, Patrick
中科院分区：
文献类型：
--
作者：
Horvath, Judit;Szalai, Istvan;De Kepper, Patrick
我们提供了实验证实的数值模拟预测自发化学机械振荡引起的pH响应水凝胶浸泡在质子自激活溴酸盐-亚硫酸盐（BS）反应的尺寸变化。凝胶在恒定和均匀的非平衡环境中膨胀和收缩，没有外部刺激。振荡既不是由反应机制中的动力学反馈引起的，也不是由长程活化扩散不稳定性引起的。动力学清楚地产生于反馈，即水凝胶的尺寸响应性对凝胶内两种不同pH梯度分布的相对稳定性施加影响。在没有凝胶尺寸变化或凝胶尺寸变化不充分的情况下，不会发生振荡。这与机械变化仅仅从属于反应动力学的系统相反。通过调节pH响应性凝胶的疏水性，显著提高了pH响应性凝胶的溶胀-消溶胀比。我们成功地产生了十几个化学机械振荡超过48小时。我们还证明了该系统能够在机械应力下工作，反复举起重量为溶胀凝胶重量10倍的物体。
We provide experimental confirmation of the numerical simulations that predicted spontaneous chemo-mechanical oscillations induced by the size-changes of a pH-responsive hydrogel immersed in the proton-autoactivated bromate-sulphite (BS) reaction. The gel swells and shrinks in a constant and uniform non-equilibrium environment, with no external stimuli. Oscillations result neither from a kinetic feedback in the reaction mechanism nor from long-range activation diffusion instability. The dynamics clearly arises from the feedback that the size responsiveness of the hydrogel exerts on the relative stability of two different pH gradient profiles inside the gel. No oscillations occur without - or with insufficient - size-change of the gel. This is opposed to systems where the mechanical changes are merely slaved to the reaction kinetics. The present progress was obtained by considerably enhancing the swelling-deswelling ratio of the pH-responsive gel by tuning its hydrophobicity. We succeeded in producing more than a dozen of chemomechanical oscillations for over 48 h. We also demonstrate that the system is capable of working under mechanical stress, repeatedly lifting an object weighing 10 times the weight of the swollen gel.