Mechano-optical response of micellar hydrogel films

Abstract

Micellar hydrogel (MHG) films exhibit polarized-light interference colors upon being stretched. Based on the results of small-angle X-ray diffraction (XRD), we proposed a new possible structural model of MHGs, where polymer chains are cross-linked by multilamellar micelles. The mechano-optical response of MHG films is attributed to the oriented multilamellar micelles induced by shear and tensile stress during stretching process. UV–vis spectra demonstrated that each visible color under polarizers results from the blending of multiple interference colors. Scanning electron microscopy (SEM) observations and birefringence measurements were used to investigate the relationship between micellar morphologies and birefringence of MHG films. It showed that the structures and morphologies of micelles determine the birefringent intensity that further influences the response sensitivity of MHG films. Rich responses can be achieved by stacking and stretching of MHG films, and desired patterns can simply be depicted into MHG films, leading to their promising applications in a variety of fields, such as digital coding and information encryption areas.