Synthesis and Physical Properties of Liquid Crystals: An Interdisciplinary Experiment
Gerald R. Van Hecke, Kerry K. Karukstis, Hanhan Li, Hansford C. Hendargo, Andrew C. Cosand, and Marja M. Fox
Department of Chemistry, Harvey Mudd College, Claremont, CA 91711
This experiment features an investigative approach designed for the introductory science or engineering major and integrates concepts in the fields of chemistry, biology, and physics. Derived from faculty research interests, this novel experiment gives students the opportunity to draw conclusions from tests performed to illustrate the connection between molecular structure and macroscopic properties. The chemical synthesis of the compounds studied further enhances the connection between molecular structure and macroscopic physical properties. The results of two separate physical measurements, refractometry and absorption spectroscopy, are combined to calculate a microscopic, but very practical, property of chiral nematic liquidsthe pitch of the helix formed in the liquid crystalline phase. This pitch depends on temperature and composition of the sample exhibiting the liquid crystalline phase, specifically the chiral nematic (or cholesteric) phase. An additional simple measurement using polarized light and a quarter wave-plate can determine the handedness of the helix.
Supplement
The complete student experimental procedures, prelaboratory assignments with solutions, a MathCad worksheet for the pitch calculations, a sample grading sheet, and extra instructors notes are available.
The "Chemistry Teacher Connection" (CTC) is especially for high school chemistry teachers. For only $40/year, it offers an online-only subscription to CLIC along with membership in the Division of Chemical Education, normally $65/year. CTC subscribers receive access to all articles and supplements from 1996 through the current issue.
Through special arrangement with the ACS, JCE High School CLIC is now able to provide subscribers with online access to Chemical & Engineering News articles that have been selected specifically for secondary science instructors and their students.
Occasionally, collections of JCE back issues become available for donation to individual teachers, schools, or libraries. JCE matches collections with interested recipients. Recipients pay shipping costs or pick up the collection.
For journals in other fields of chemistry visit ACS Publications.
Contents
Always in the