TABLE OF CONTENTS This chapter reviews past research that has applied methods in optical rheometry to solve problems in the structure and dynamics of complex liquids. This review is organized according to the types of complex liquids that have been studied. In addition, several case studies are provided where the reader is introduced to specific applications that have been chosen to highlight various optical techniques and the interpretation of data. Those studies chronicle the execution of the experiment, including the motivation of the choice of a particular technique, the design of the instrumentation, and the experimental procedures.
Early work on the use of optical methods on the dynamics of polymeric liquids focused on establishing the validity of the stress-optical rule. A comprehensive account of this research can be found in the books by Janeschitz-Kriegl [29] and Wales [84]. Tlio majority of studies have considered simple shear flow, and the rule has been found to hold Up to stresses up to 10 4 Pa. Such tests have not only considered the linearity of the shear stress with ? n ? sin 2 ?, but also the coaxiality of the stress and refractive index tensor by ensuring that the extinction angle, ?, obeys the relation: tan2 ? = 2 ? xy/ N 1. In a polymer melt, a violation of the rule would be expected if chain orientation became sufficiently high to cause a departure in gaussian chain statistics.
