Annealing of shape memory polymer
Movie showing the shape recovery of a polystyrene (PS) microparticle during annealing. Imaged using tapping mode on a MFP-3D with scan size 15 μm. The PS particle was flattened with a high-temperature, high-pressure nanoimprint lithography (NIL) process and then thinly coated with gold. The movie starts with the particle heated to 80°C. The temperature is rapidly stepped to 102°C, then over the course of three hours the temperature is gradually increased to 110°C. During annealing the particle diameter decreases and the height increases, recovering the original, pre-NIL spherical shape. A surface wrinkling morphology develops that gives information on recovery dynamics and strain energy release. Applications for micro- and nanoscale polymer particles include drug delivery and electronic packaging; incorporating shape memory effects could lead to many more. Data courtesy of Jason Killgore (NIST) and Lewis Cox (University of Colorado-Boulder). Adapted from L.M. Cox, J.P. Killgore, Z. Li, Z. Zhang, D.C. Hurley, J. Xiao, and Y. Ding, Adv. Mater. 26, 899 (2013).