Shape-changing polymers undergo mechanical deformations in response to changes in their environment. As technology continues to become smaller and more efficient, systems that can exploit environmental changes to perform functions become more attractive for biomedical applications. In liquid crystalline polymer networks, shape change is directed by the local molecular order. This molecular ordering can be spatially patterned, resulting in monolithic materials that undergo complex shape change. However, liquid crystal polymer networks are typically hydrophobic and only respond to stimuli that would be incompatible with biological environments, such as high temperatures and organic solvents. Chromonic liquid crystals are a type of lyotropic liquid crystal which exhibits ordering in aqueous environments. We have recently shown that we can orient crosslinked, chromonic hydrogels. By incorporating temperature-responsive comonomers, such as n-isopropylacrylamide, gels can be synthesized that undergo reversible, anisotropic shape change over the near physiological temperature range. We present our work building on these initial results to increase the amount of reversible shape change and increase the control over the molecular ordering. By controlling the crosslink density of the gel, we increase the volumetric shape change observed on heating from 25 °C to 70 °C from ~65% to ~450% (Figure 1). This shape change remains anisotropic despite the large volume change. Additionally, we utilize the patterning of surfaces to manipulate molecular orientation in these chromonic gels for control over the shape change. To evaluate these gels for potential biomedical devices, we also present results from biocompatibility studies.

Chromonic liquid crystal hydrogels with patternable, high strain actuation for biomedical applications

254th National Meeting (2017)

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