Novel pH-sensitive hydrogel fibers based on hydrolyzed polyacrylonitrile and gelatin

Novel smart hydrogel fibers were prepared from a blend of hydrolyzed polyacrylonitrile (H-PAN) and gelatin (Ge) with various compositions. From the observation by SEM, it was found that H-PAN/Ge hydrogel fibers consisted of a porous structure. The dynamical elongation/contraction behavior was studied in response to a sudden pH change. The significant results obtained were as follows: (i) With an increase in the content of Ge, the hydrogel fibers exhibited excellent reversible pH-sensitive behavior in terms of response times in elongation and contraction. When W-PAN : W-Ge = 3 : 7, the fibers showed the best response times at 0.95 s (elongation) and 1.14 s (contraction). (ii) The contraction response time of every hydrogel fiber was longer than its elongation response time. (iii) The equilibrium swelling elongation decreased gradually with the content of Ge increasing. These results were found to be explicable in terms of the surface morphology and polyampholytic properties of H-PAN/Ge hydrogel fibers.