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.