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

建立了电激活人工肌肉系统的模型，该系统在等温条件下可通过电刺激可逆地收缩和扩张。当通电时，聚合物凝胶开始收缩，并释放出一个又一个水滴。电收缩凝胶的最小电场强度为1-2 V/cm，水的释放速率随电场强度的增加而增加，能自动反复升降负载的机械力化学系统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率增加了负载。因此，22 g的重量比5.5g的重量快6倍。22 g凝胶的做功效率是5.5g凝胶的24倍。凝胶的这种反常的提升行为可以用可电离基团的自发电离来解释，当凝胶被拉伸时，可电离基团的自发电离导致电流增加（逆机械化学反应）。我们发现夹在两个铂丝电极之间的金属/聚合物凝胶/金属结构具有可逆的开关功能。存在一个“潜力阈值”。低于该值（在该实验中约3V/cm或更低），甚至通过长时间的实验也几乎不出现振荡。在阈值电位以上和诱导期后，具有离子化基团的交联水溶胀聚合物凝胶均出现无阻尼振荡。

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.