Improvement of multiple-responsive shape memory effects of wool through increasing the content of disulfide bonds

As an ideal smart wearable natural material, α-keratin type mammalian hairs have proved to exhibit multiple-responsive shape memory effects under water, wet, xenon and redox stimuli, in which the inherent disulfide bonds played the roles of either netpoints or switching units. Accordingly, here in this work, we proposed to increase the content of disulfide bonds of representative mammalian hairs - wool fibers , which are widely used in daily life, by means of three chemical methods so as to improve their multiple-responsive shape memory effects. On the basis of systematic researches, it was found that the treatment with cystamine gave the highest efficiency of introducing disulfide bonds due to full use of the free functional groups of wool, while the valuable crystalline phases of wool were nearly not affected. As a result, the cystamine modified wool fibers possessed greater shape recovery ratio under water and heat conditions, and larger shape fixation ratio under xenon and redox conditions , in comparison with the untreated version. The mechanisms involved were carefully analyzed. The application scope of the on-demand programmed wool in intelligent fabrics and textiles would thus be broadened.