(723a) An Integrated Theoretical and Experimental Approach to the Design of Liquid Crystal-Based Chemical Sensors

Authors: 
Roling, L. T., University of Wisconsin-Madison
Bedolla, M., University of Wisconsin-Madison
Choi, S., University of Wisconsin-Madison
Twieg, R., Kent State University
Abbott, N. L., University of Wisconsin-Madison
Mavrikakis, M., University of Wisconsin-Madison

Surface-anchored nematic liquid crystals can undergo orientational changes in response to select chemical stimuli, presenting opportunities for the design of highly sensitive chemical sensors. We present an approach to materials design that combines theoretical predictions, synthesis, and experimental characterization and evaluation for the accelerated discovery of new sensor materials. Our previous work has shown that the surface-induced ordering of the liquid crystal 4-cyano-4’-pentylbiphenyl (5CB) depends strongly on the chemical functionality of the surface, and that an orientational change can be triggered by the presence of small molecules such as dimethyl methylphosphonate (DMMP).1-3We developed a computational model for this process, based on quantum mechanics, showing that orientational changes can be predicted on the basis of the relative binding energies of the 5CB and DMMP to the metal cation-functionalized surfaces.

In this presentation, we will describe the use of our computational model to design new classes of liquid crystal-based sensor materials for detection of a wide range of small molecules, by varying the chemical functionalities of liquid crystals as well as the metal cations used in the metal surfaces. We present a number of promising candidate sensors for detecting NO2, acetone or ClO2on the basis of their relative binding energies to metal cations. Motivated by our calculations, we have successfully synthesized new liquid crystals with desired chemical functionalities, and experimental evaluation has confirmed the validity of several predictions for enhanced sensor materials. Additionally, we have used thermogravimetric analysis (TGA) and temperature-programmed desorption (TPD) to directly measure the strength of binding of mesogens to metal ions, and used these measurements to evaluate computational predictions.   

1. Shah, R. R.; Abbott, N. L., Science 2001, 293, 1296.
2. Hunter, J.T.; Abbott, N.L., Applied Materials and Interfaces, 2013, 6, 2362
3. Yang, K. L.; Cadwell, K.; Abbott, N. L., Journal of Physical Chemistry B, 2004, 108, 20180.