To the mechanism of polyelectrolyte gel periodic acting in the constant DC electric field

• Unexpected periodic bending of polyelectrolyte gels in DC electric field was studied.
• Geometrical dimensions of the gel stripe in the course of its acting were monitored.
• Misbalance between the cathodal and the anodal contraction of gel was found.

If the elongated filament of sodium polyacrylate gel immersed in 0.8 mM CaCl2 solution is placed in a DC electrical field across the field lines with one end affixed, up to four consequent sways of strip's free end can be observed. This phenomenon is still not clear as it takes place in the constant electric field with the constant polarity. To disclose underlying mechanism of the periodic bending, angle of the gel free end displacement (inclination) from the vertical (initial) position, the apparent area and the lengths of the cathodal and anodal borders of the projective image of the gel stripe were monitored. It was found, both the cathodal and the anodal sides of the stripe followed the trend of the gel shrinkage, but with a substantial time lag between them. The misbalance between the cathodal and the anodal contraction of the gel resulted in the strip periodic acting. The underlying mechanism of this phenomenon based on ionic diffusion and ionic exchange due to oriented ionic flux in a DC electric field is proposed.