"A Universal platform for the introduction of sensitive molecules in liquid crystal elastomers"

J. Guillen Camposa, M. Parka, S. Sandlassb, E. Novikova,c, Y. Wua and J. Read de Alaniza

a Department of Chemistry and Biochemistry, University of California, Santa Barbara, 93106 / b Department of Chemical Engineering, University of California, Santa Barbara, 93106 / c Department of Chemistry , New Mexico Highlands University, Las Vegas, New, Mexico, 87701 USA

Liquid crystal elastomers (LCEs) are a class of materials capable of exhibiting strong mechanical responses to external stimuli.1 Added to this, when these systems are enhanced by covalently attaching photoswitches, due to the nature of these molecules, multiple responses (spectroscopical, structural, thermal, hydrophobic/hydrophilic, ionic, pH etc.) are seen. Given this elementary concept, photoswitches have been introduced in LCEs in many reports to show simultaneous response to light, temperature, humidity, etc.2 however, every time a new photoswitch is introduced, it is done on a specific polymer matrix through a specific polymerization technique that yields a very unique material uncapable of comparing or standardizing to the rest of materials previously done in the literature.3 It exists a lot of potential in fusing these photoswitches and LCEs field, however, due to the chemically sensitive nature of photoswitches and the chemically harsh conditions used to polymerize these liquid crystal elastomers, to this day, no platform capable of bringing these two fields together has been developed.

In this work, a universal platform capable of introducing sensitive photoswitches in LCEs is developed. Azobenzenes, Spiropyrans, Donor-acceptor Stenhouse adducts, and highly absorbing organic dyes are covalently introduced in liquid crystal elastomers enabling novel responses of these family of materials.

Simultaneously, we believe that this work has the potential to develop fundamental studies on the force produced by the mechanochemical isomerization of these photoswitches that will allow, for the first time, to quantify the mechanical work output done by each single molecule of the photoswitch.

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References:

  1. J. Kiipfec, H. Finkelrnann. Makromol. Chem. Rapid Commun. 1991, 726, 717–726.
  2. O. M. Wani, R. Verpaalen, H. Zeng, A. Priimagi, A. P. H. J. Schenning, Adv. Mater. 2019, 31, 1805985.
  3. T. S. Hebner, M. Podgórski, S. Mavila, T. J. White, C. N. Bowman, Angew. Chem. Int. Ed. 2022, 61, e202116522.