Taming Macromolecules by Light – Supramolecular Photoresponsive Materials at Three Different Length Scales

Speaker 

Jaana Vapaavuori, Université de Montreal

Abstract 

When noncovalently bound to macromolecules, photoisomerizing molecules can be harnessed for controlling the properties of materials at length scales spanning at least three orders of magnitude. In this presentation, I will discuss my recent work seeking fundamental understanding of how the nanometer-scale photoinduced changes in azobenzene and spiropyran derivatives can be translated into different applications involving polymers. First, starting from the length scale of 10-100 nm, the morphology of self-assembled diblock copolymers can be switched by supramolecularly attaching azobenzene molecules selectively to one of the blocks upon dip-coating nanostructured thin films. Similarly, the size of diblock copolymer micelles, consisting of a neutral and polyzwitterionic blocks, can be doubled upon photoisomerizing spiropyran guest into its merocyanine form. Second, I will discuss the supramolecular material design guidelines of how azobenzene motion is converted into all optical surface patterning resulting in micron-scale surface reliefs. Third, stimuli-induced changes visible at the macroscopic scales are discussed, by introducing supramolecular polymer-azobenzene humidity memories and light-switchable polymer wrinkles at the scale of approximately 10-100 μm. This presentation highlights that the key to achieving high-tech applications is to first understand the delicate balance of supramolecular interactions in soft condensed materials, and then develop methods for controlling them.