Programmable mechanically assisted geometric deformations of glassy two-stage reactive polymeric materials.

Thiol-isocyanate-methacrylate two-stage reactive network polymers were developed and used for fabrication of well-defined surface patterns as well as functional geometric shapes to demonstrate a new methodology for processing of "smart materials". The dynamic stage I networks were synthesized in base-catalyzed thiol-isocyanate cross-linking reactions to yield tough, glassy materials at ambient conditions. Methacrylate-rich stage I networks, incorporating photoinitiator and photoabsorber, were irradiated with UV light to generate stage II networks with intricate property gradients. Upon directional straining and subsequent temperature-dependent stress relief of the predefined gradient regions, the desired surface or bulk geometric transformations were achieved. Depending on the gradient extent in conjunction with photoorthogonal initiators, the introduced deformations were shown to be easily erasable by heat or permanently fixable by bulk polymerization.