One goal for next-generation adaptive materials is to be able to transition reversibly between liquid to solid behavior in response to stress. Concentrated suspensions of solid particles dispersed in a liquid can achieve this stressadaptive response by developing microstructures that lead to dramatic increases in viscosity or even solidification under shear (shear jamming).
To be able to tune this response with temperature, a collaboration between the de Pablo, Rowan and Jaeger groups at the University of Chicago developed a novel class of suspensions with stimuli-responsive polymer particles. Particles were designed with easily accessible polymer glass transition temperatures around which the particle stiffness undergoes a 3 orders of magnitude decrease. This drives large changes in the suspension’s shear thickening strength and makes it possible to turn shear jamming on or off.
These results lay the groundwork for utilizing the glass transition in polymeric particles to engineer suspension-based material systems that have adaptive, and ultimately trainable, mechanical properties. Designing materials with trainable functionality is the central aim of IRG 1 on Trainable Soft Matter.
(In suspensions of polymer particles designed to undergo a glass transition, the ability to shear jam can be turned on (or off) in situ by varying temperature. Images show pull tests.)
“Leveraging the polymer glass transition to access thermally-switchable shear jamming suspensions,” Chuqiao (Elise) Chen, M. van der Naald, A. Singh, N. Dolinski, G. Jackson, H. Jaeger, S. Rowan, J. de Pablo, ACS Central Sci. 9, 639–647 (2023)