Contraction of Water-Swollen Polymer Gels by Electric Stimulus and Its Application to Mechanochemical Devices.

建立了等温条件下电刺激可逆收缩和扩张的人工肌肉系统模型。通电后，聚合物凝胶开始收缩，随时释放出一个又一个水滴。凝胶收缩的最小电场为1~2V/cm，释水率随外加电场的增加而增大。机械力化学系统可自动多次升降负荷，是电收缩凝胶最简单的应用。最有趣的特征是，凝胶的收缩速度增加了负荷。因此，22克的重量举起的速度是5.5克的6倍。该凝胶在22g负荷下的作功效率是5.5g负荷下的24倍。这种异常的凝胶提升行为可以用凝胶拉伸时可电离基团的自发电离导致电流增加(反向机械力化学反应)来解释。我们发现，夹在两个铂丝电极之间的金属/聚合物凝胶/金属结构具有可逆开关的功能。电势存在一个“阈值”，低于这个阈值(在本实验中约为3V/cm或更低)，即使长时间的实验也几乎没有出现振荡。在阈值电位以上和诱导期后，每一个闭合的水溶胀聚合物凝胶都出现了无抑制的振荡，只要它们具有电离部分。

The model of electrically activated artificial muscle system which contracts and dilates reversibly by electric stimulus under isothermal condition was developed. When the electricity was tured on, the polymer gel started to shrink readly releasing water droplet on after another. The minimum value of electric field to induce contraction of the gel was 1-2 V/cm and the rate of water release increased with increasing electric field imposed.Mechanochemical system capable of lifting a load up and down automatically and repeatedly is the simplest application of electro-shrinkable gels. The most interesting feature was that the rate of contraction of the gel increased load. Thus, a weight of 22g was lifted 6 times faster than one of 5.5g. The efficiency of the work done by the gel with 22g load was 24 times lager than that with a 5.5g load. This anomalous lifting behavior of the gels can be explained in terms of a spontaneous ionization of ionizable groups leading to an increased electric current when the gel is stretched (reverse mechanochemical reaction).We found that matal/polymer gel/metal structure sandwiched between two platinumwire electrodes, has a function switching on and off reversibly. There existed a "threshold value of potential. Below this value (in this experiment about 3 V/cm or below) practically no oscillation was appeared even by prolonged experiment. Above the threshold potential and after inductive period the undamped oscillations were appeared in every closslinked water-swollen polymeric gels provide they possesses ionized moieties.