REPORT OF SCIENCE
AT
WILLIAMS COLLEGE
1999 - 2000
A RECORD OF THE PROFESSIONAL ACTIVITIES OF
FACULTY AND STUDENTS IN THE NATURAL SCIENCES
Williamstown, Massachusetts
2000
Optical Texture of a Liquid Crystal Viewed under
Cross-Polarizers
Liquid crystals (LC's) are materials that
exhibit properties intermediate between the crystalline solid and
isotropic liquid phases. The combination of molecular order found in
crystalline solids with the fluidity of a liquid phase results in a
material whose optical properties may be switched on and off by
application of external magnetic or electric fields, or as a function
of temperature. This "switchability" is responsible for the
wide-spread application of liquid crystals in various optical display
devices.
A number of Williams students (most recently
Mark Walrod ’01, Maria Drinane ’02, and Marsha Lynch ’03)
have been working with Professor Lee Park of the Chemistry Department
to design new LC materials based on simple metal complexes which can
aggregate into one-dimensional structures. By chemical derivatization
of known metal complexes, they are working to take advantage of the
properties of the LC phase as a means of overcoming specific
obstacles associated with one-dimensional materials. Once
synthesized, their materials are characterized by a number of
techniques, including polarized optical microscopy. The cover
photograph illustrates the optical texture of a material as it is
cooled from the isotropic fluid phase, and enters the temperature
range of the liquid crystal phase. The dark areas are regions in
which the material is still in the normal liquid phase, while the
colored areas are those where the liquid crystal phase is present.
The specific patterns and colors exhibited are indicative of the
exact type of intermolecular ordering present in the material, and
provide a means of assessing both the stability of new liquid
crystalline materials as well as their potential as one-dimensional
conductors.