Nature creates macroscale materials with enhanced mechanical properties through assembly of mesoscale building blocks, which impart inherent anisotropies and complex stimulus response. Synthetic replication of these building blocks holds promise for development of advanced materials, yet few strategies exist to achieve mesoscale structural control. Moreover, compared to countless examples of complex patterning at other length scales, specifically the nanoscale, mesoscale materials have received little attention. Realizing such systems will require both innovative fabrication methods and smart, stimulus-responsive chemistries to yield precise architectural control. Towards this objective, we take inspiration from systems at the nanoscale, particularly block copolymers, which are well established in their utility as periodic building blocks for intricate self-assembled systems. To translate this behavior to the mesoscale, we have developed ribbon-like structures, termed mesoscale block copolymers (MSBCPs), that feature covalently-bound segments of alternating chemical composition, and are nanometers in thickness, micrometers in width, and millimeters to centimeters in length. MSBCPs are prepared by combining a bottom-up solution fabrication technique with materials containing photo-activated chemical triggers for post-fabrication patterning. Upon release from the substrate into an aqueous dispersion, selected MSBCP segments respond to changes in the surrounding fluid environment by coiling into helices. The remaining segments, composed of a different material, are inert to the selected stimulus and remain in an extended ribbon conformation. These alternating ribbon-helix structures are analogous to rod-coil block copolymers, yet exist on length scales that allow characterization by optical techniques. Moreover, the employed fabrication method can produce thousands of ribbons in a single batch, offering a potential platform for self-assembled materials built from mesoscale block copolymers.

Mesoscale block copolymers

255th National Meeting (2018)

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