Color changing polymers responding to deformation
Sean Woodward, Cristina Schlesier, Robert Uhrlass, Petr Shibaev, PhD
Department of Physics
Abstract
Novel cholesteric liquid crystalline (CLC) materials whose selective reflection bands
experience a downward shift in wavelength in response to uniaxial strain are designed
and studied. CLC materials have a helical structure and their helical pitch determines the
range of wavelengths (selective reflection band) in which light with the same sense of
polarization as their helical structure is reflected. The liquid crystal samples were spread
onto individual silicone strips or inserted between their pairs, which were the direct
subjects of stretching. Color change occurred instantaneously in all samples, though color
relaxation back to initial was a positive function of viscosity. In a related experiment we
observed that optical pumping of these materials doped with laser dyes produced lasing at
wavelengths that depended upon strain and varied by as much as 80nm within the
emission interval(s) of the laser dyes. We propose a quantitative model accounting for the
shift in the selective reflection band with stretching that treats the cholesteric material as
an incompressible viscoelastic fluid.
Presenter Bio
SeanWoodward is in his final year of pursuing a double-major in physics and biology at
FCRH. He has participated in research projects of various focus in both the
aforementioned fields, but hopes to eventually enter the area of theoretical (i.e.,
mathematical) biology - particularly computational neuroscience - after pursuing further
graduate work in physics and/or mathematics.