Using Piezoelectricity to Make Force-Responsive Polymeric Materials

Stimuli-induced polymerizations continue to gain interest as synthetic polymers become more desirable for materials, industrial, and medical applications. While traditional stimuli such as heat, light, and electrochemistry have been extensively studied, they still have shortcomings such as unwanted side reactions, lack of consistent penetrability, and irregular and irreproducible equipment setups. Additionally, high energy inputs and large amount of solvent are regularly used with such stimuli. Many of these shortcomings can be overcome by using force as a stimulus for polymerization. As has been shown in organic small molecule synthesis, the use of piezoelectric nanoparticles enables force to initiate redox reactions, thus making force an even more useful, accessible, and sustainable stimulus for polymerization chemistry.<br/>Herein, we show iodonium salts can initiate free and controlled radical polymerizations of acrylates upon the introduction of various types of force in the presence of piezoelectric nanoparticles, consuming less energy and solvent than traditional polymerization methods. These salts have demonstrated to be reactive with piezoelectric nanoparticles and useful in synthesizing high molecular weight polymers with relatively low dispersities. Furthermore, these polymerizations have been effectively carried out in both solid and solution states with multiple force sources, including ultrasound, ball milling, and vortexing. Preliminary data also indicates that force might be a new useful tool for crosslinking materials and for force-curing in additive manufacturing taking advantage of the mentioned multiple force sources. This iodonium initiated mechanoredox chemistry unlocks the possibility to better utilize force in synthesizing polymers and creating useful adaptable materials.<br/><br/>Acknowledgements: This work was supported by a seed grant from UW MEM-C, an NSF MRSEC funded under DMR-1719797<br/><br/>(1) Kubota, K.; Pang, Y.; Miura, A.; Ito, H. <i>Science.</i> <b>2019</b>, <i>366</i>, 1500–1504.; (2) Mohapatra, H.; Kleiman, M.; Esser-Kahn, A. P. <i>Nat. Chem.</i> <b>2017</b>, <i>9</i>, 135–139.; (3) Wang, Z.; Ayarza, J.; Esser-Kahn, A. P. <b>2019</b>, <i>58</i>, 12023–12026.; (4) Wang, Z. Z.; Pan, X.; Yan, J.; Dadashi-Silab, S.; Xie, G.; Zhang, J.; Wang, Z. Z.; Xia, H.; Matyjaszewski, K. <i>ACS Macro Lett.</i> <b>2017</b>, 546–549. (5) Zeitler, S.; Chakma, P.; Golder, M.<i> Chem. Sci.</i> <b>2022</b>, <i>13</i>, 4131–4138. (6) Chakma, P.; Zeitler, S. M<b>.</b>; Baum, F.; Yu, J.; Shindy, W.; Pozzo, L.; Golder, M. <i>Angew. Chem. Int. Ed. </i><b>2022. </b>Accepted Article