The evolution of self-wrinkles in a single-layer gradient polymer film based on viscoelasticity

Understanding the evolution of self-wrinkling is critical to control the wrinkles that widely exist in nature and engineering. Using a single-layer film of photosensitive anthracene-functionalized poly(styrene-block-butadiene-block-styrene) (SBSAn) as a model, we investigated the generation of self-wrinkles on this film. Upon irradiation with UV light, the SBS-An film was designed to achieve a gradient structure with controllable elasticity and viscoelasticity. The inner stress is produced via UV-lightinduced cross-linking, which drives the wrinkling. Importantly, the evolution of the wrinkles in this gradient film was a timedependent kinetic process, which was traced by a microscope to understand the mechanism of wrinkling based on the polymer viscoelasticity. Theoretical calculations and simulations were also utilized to verify and support the experimental results. Furthermore, taking advantage of light, the precise temporal and spatial control of wrinkles could be achieved by photochemical boundaries, which permit various ordered wrinkles.