Stretchable optical diffraction grating from poly(acrylic acid)/polyethylene oxide stereocomplex

Optical gratings are a key component in many spectroscopy, communications, and imaging systems. While initially static elements, advances in optical materials have enabled dynamically tunable gratings to be designed. One common tuning strategy is relying on mechanical deformation of the grating pitch to modify the diffraction pattern. To date, most mechanically adaptive optical gratings consist of a hybrid system where rigid moieties are patterned on an elastomeric substrate. In the present work, we demonstrate an all-polymer tunable grating that is fabricated using replica molding from the poly(acrylic acid) (PAA)/polyethylene oxide (PEO) polymer stereocomplex. PAA/PEO pristine films exhibit excellent optical transmittance at or above 80% from 500 nm to 1400 nm and stretchability over 800% strain. The experimental studies on the changes of diffraction mode distances with respect to the applied strains agree well with the finite-difference time-domain (FDTD) theoretical modeling.