WRINKLING AS A PROBE OF RELAXATION DYNAMICS IN ULTRATHIN GLASSY POLYMER FILMS
Jun Young Chung and Christopher M. Stafford
Polymers Division, Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899
Surface instabilities in soft matter have been the subject of increasingly innovative research efforts aimed at better understanding the physics of their formation and the application for such phenomena in patterning and organizing materials on the micro- to nano-scale. Recently, surface instabilities have also shown considerable promise as a method for characterizing the properties of a wide variety of thin-film materials systems due to the ease and speed with which measurements can be performed. In this presentation, we focus on a type of instability known as ‘surface wrinkling’ and demonstrate how surface wrinkling is poised to address a variety of complex measurement needs for advanced materials science systems, and how the wrinkling-based technique is leveraged to measure the dynamically changing properties of thin-film materials. In particular, we highlight a recently developed in-situ method for measuring the rate of structural relaxation in ultrathin (< 100 nm) glassy polymer films by probing the temporal decay of strain-induced wrinkling patterns back to their flat equilibrium state. We present details of how such a method enables the determination of the thickness- and temperature-dependent characteristic relaxation time and high frequency Young’s modulus in a relatively simple manner.