Rheo-optical methods

P. L. Frattini and G. G. Fuller, A note on phase-modulated flow birefringence a promising rheo-optical method, J. Rheol., 28 61, (1984). 

Polymer liquid crystals generally form unusual textures, accompanied by complex and unstable superstructures. Such textures depend on a sample history, especially mechanical and thermal histories, and also on the surface nature of the vessels. We have described the structural characteristics of polymer liquid crystals under a shear force by means of rheo-optical methods. ... 

Generally, from spectroscopic data such as frequency position, band shape, intensity and dichroism of specific absorption bands conclusions can be derived in terms of the applied mechanical stress and the state of order and orientation of the polymer under investigation. An extremely powerful method for the study of transient phenomena in polyuMr deformation and relaxation is rheo-optics which describes the relation between stress, strain and an optical quantity (for example birefringence, infrared absorption, light scattering. X-ray diffraction) measured simultaneously with stress and strain as a function of time In a given rheo-optical method therefore, a mechanical test is combined with one of these various types of optical measurements. 

Rheo-optical methods provide a unique opportunity to examine the spatial and temporal evolution of the stresses in a liquid an example was given in Figure 9.1.1 (Han, 1981). A second example is shown in Figure 9.5.1 (Fuller, 1990). Here the birefringence was monitored as a fimction of time at various distances from the outer, rotating wall in a Couette cell. The rotation rate was stepped from... 

Treloar studied all aspects of mbber science, and was elected to the Rubber Science Hall of Fame in 1987, upon his death. He made careful studies of the crystallization of natural mbber. He used rheo-optical methods to study the local anisotropy of stretched mbber. He was a brilliant experimentalist and made seminal measurements of deformation in many different geometries. Treloar was... 

The principle of rheo-optics is illustrated in Figure 1. Rheo-optical methods involve simultaneous measurement of both rheological and optical properties of a system to elucidate its complex rheological properties on the basis of the responses of the fundamental strucmral units of the system. After applying mechanical excitations to the system, the mechanical responses are detected and analyzed. Rheology clarifies the law of causality between mechanical stimuli and responses. Simultaneously, optical responses or responses of stmcture factors are also... 

DIRLD spectroscopy belongs to the characterization techniques known as Vheo-optics. Rheo-optical analysis of materials utilizes electromagnetic probes in conjunction with application of macroscopic mechanical perturbations. It investigates primarily the microscopic or molecular responses of materials under deformation, flow, and relaxation. In dynamic rheo-optical methods, such as dynamic birefringence, light scattering, and X-ray diffraction, relationships... 

Since the early pioneering period, the methods have been enormously advanced in the fields of not only polymer science but also soft-matter sciences in general. Therefore, it is quite timely to introduce the rheo-optical methods in this new version of Polymer Science A Comprehensive Reference. However, it should be stressed that the articles presented in Section 2.30.2 and Section 2.30.3 of this chapter cover only a part of the advances in the respective scientific fields. 

In this chapter, the rheo-optical methods in the mesoscopic scale were described in Section 2.30.2 and those in the sub-molecular scale in Section 2.30.3, for separate systems. The authors would like to encourage the next generation of rheo-optics researchers to simultaneously apply the two methods, covering both the mesoscopic and the submolecular scales, to the same system. This is indispensable for a further integral and systematic understanding of the structural and rheological responses against applied fields. 

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