Color Changing Cholesteric Polymer Films Sensitive to Amino Acids

Abstract

Chiral hydrogen-bonded polymer films that respond to the presence of some amino acids (arginine, lysine, histidine) in water by changing the color and shifting the wavelengths of the selective reflection band (SRB) were synthesized and studied. The kinetics of the film's response depends on the concentration of donor/acceptor groups in the polymer matrix. A higher concentration of hydrogen-bonded groups results in a faster shift of the SRB and color changes. This effect is explained in terms of structural changes and the breakage of hydrogen bonds that occurs between the components of a cholesteric polymer, immersed in various aqueous solutions of amino acids. Optical pumping of cholesteric films doped with laser dyes leads to lasing. The changes in the selective reflection induced by amino acids in water solutions result in a shift of the lasing wavelength.