Browsing by Author "Chipara, Alin C."

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    Dynamic Self-Stiffening in Liquid Crystal Elastomers
    (Nature Publishing Group, 2013) Agrawal, Aditya; Chipara, Alin C.; Shamoo, Yousif; Patra, Prabir K.; Carey, Brent J.; Ajayan, Pulickel M.; Chapman, Walter G.; Verduzco, Rafael
    Biological tissues have the remarkable ability to remodel and repair in response to disease, injury and mechanical stresses. Synthetic materials lack the complexity of biological tissues, and man-made materials that respond to external stresses through a permanent increase in stiffness are uncommon. Here we report that polydomain nematic liquid crystal elastomers increase in stiffness by up to 90% when subjected to a low-amplitude (5%), repetitive (dynamic) compression. Elastomer stiffening is influenced by liquid crystal content, the presence of a nematic liquid crystal phase and the use of a dynamic as opposed to static deformation. Through rheological and X-ray diffraction measurements, stiffening can be attributed to a mobile nematic director, which rotates in response to dynamic compression. Stiffening under dynamic compression has not been previously observed in liquid crystal elastomers and may be useful for the development of self-healing materials or for the development of biocompatible, adaptive materials for tissue replacement.
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    Fluorine and hydrogen-based adhesive compositions and methods of making the same
    (2021-11-16) Chipara, Alin C.; Chipara, Mircea; Tiwary, Chandra S.; Ajayan, Pulickel M.; Rice University; The Board of Regents of The University Of Texas System; United States Patent and Trademark Office
    Embodiments of the present disclosure pertain to adhesive compositions that include a fluorinated molecule and a hydrogen-containing molecule that are non-covalently associated with one another. The molecules may be non-covalently associated with one another through dipole-dipole interactions that create a fluorine-hydrogen electronegativity difference between at least some of the fluorine atoms of the fluorinated molecule and at least some of the hydrogen atoms of the hydrogen-containing molecule. The fluorinated molecule and the hydrogen-containing molecule may be in different phases, such as a liquid phase for one molecule and a solid phase for the other molecule. Additional embodiments pertain to methods of enhancing an adhesiveness of a surface by applying an adhesive composition of the present disclosure to the surface. Further embodiments pertain to methods of making the adhesive compositions by mixing a fluorinated molecule with a hydrogen-containing molecule such that the molecules become non-covalently associated with one another.