Elongation/contraction properties for poly(acrylonitrile) gel fibers stimulated by pH

Abstract Fine gel fibers were prepared from commercially available poly(acrylonitrile) (PAN) fibers by preoxidation and hydrolysis. C 13 NMR and WAX analysis showed the chemical structure of the PAN gel fibers consisted of the planar network structure with pyridine rings and carboxyl groups. The PAN gel fibers showed large elongation in an alkaline solution and contraction in an acidic solution. The degree of swelling in length under an isotonic load was about 80% and the response times in contraction/elongation behavior were about 2 and 4 s, respectively. The ultimate contraction energy and the power were about 188 mJ/cm 3 and about 22 mW/cm 3 , respectively. The maximum contraction force under an isometric state was about 1·2 MPa. The degree of swelling in length, the contraction time and the contraction force were mainly dependent on the aromatization index (AI) in the PAN gel fibers. pH hysteresis loops in the contraction/elongation behavior for the PAN gel fibers stimulated by pH were found.