Electrically Driven Chemomechanical Polymer Gels as Artificial Muscle

我们开发了一种新型的电驱动化学机械系统，它具有动态响应快的特点。这一运动的原理是基于溶剂化阳离子表面活性剂N-十二烷基吡啶氯化物(C12PyCl)从聚(2-丙烯酰胺基-2-甲基丙磺酸)(PAMPS)到交联聚合物凝胶模式的电动分子组装反应，这本质上是一个化学计量离子交换反应，具有两个过程。一种是表面活性剂分子在凝胶中与相反电荷的磺酸盐形成静电盐(引发过程)。另一种是结合表面活性剂之间的疏水相互作用，它稳定聚集体，例如沿着聚合物链在已占据的位置附近沉淀(传播过程)。后者被称为“合作过程”。在这里，电场驱动和控制平衡的方向，以产生各向异性结合，即当直流电压打开时，表面活性分子通过电泳向阴极移动，并优先与PAMPS凝胶条面向阳极的一侧的凝胶结合。这会导致凝胶的各向异性收缩并向阳极弯曲。因此，通过施加每隔两秒改变其极性的电场来进行凝胶的摆动。该凝胶具有柔和灵活的运动特性，可作为一种不同于液压发动机和金属机械的新型软执行器或分子机械。

We have developed a new type of electrically-driven chemomechanical system which shows quick responses with motility. The principle of this movement is based on an electrokinetic molecular assembly reaction of solvated cationic surfactants, N-dodecylpyridinium chloride (C12PyCl), onto the crosslinked polymer gel mode from poly(2-acrylamido-2-methylpropane sulfonic acid)(PAMPS), which is essentially a stoichiometric ion exchange reaction characterized by two processes. One is electrostatic salt formation of surfactant molecules with oppositely-charged sulfonates in the gel (initiation prosecc). The other is a hydrophobic interaction between bound surfactant, which stabilizes the aggregate in such as settle at the adjacent to the already occupied site along the polymer chain (propagation process). The latter is called as "cooperative process". Here, the electric field drives and controls the direction of the equilibrium to give anisotropic binding, i.e., when the dc.voltage is turned on, the surfactant molecules move towards the cathode by electrophoresis and bind with the gel preferentially on the side of the PAMPS gel strip facing the anode. This causes an anisotropic contraction of the gel and bending towards the anode. Thus, a swinging of the gel was performed by applying electric field changing its polarity every two seconds. The motility of the gel is gentle and flexible and can serve as a new class of soft actuator or molecular machine different from hydraulic engine and metallic machine.