Structure and properties of macromolecules in shearflow

Abstract

A laser light-scattering photometer is presented, the construction of which is based on the principle of a searle-type viscosimeter. It permits registration of the wideangle distribution of the scattered light in an area of 1 ~ sr around the direction of the negative velocity gradient with high resolution (49 9 10 -6 sr).In the investigated range (0-3000 s -i) the scope of shear-induced intensity changes of diluted solutions of polystyrene in benzene is 0.5-5 %. The alignment, controland measurement of several influencing factors, e. g. the positional and intensity stability of the primary beam, required a relatively high degree of performance.The relation of the intensity changes of the scattered and transmitted light are measured and illustrated as a function of shear cycles. In this way it is possible to recognize both the orientation and the deformation as well as the relaxation of shear-stressed PSmolecules. The discussion of the curves is guided by a simple instructional preview.

Light scattering from dilute polymer solutions in shear flow

“…The outer cylinder of the shear cell and the bottom and cap plates are made of optical glass (Heraeus, Germany), while the Light Scattering from Dilute Polymer Solutions 465 inner cylinder is made of nickel-plated, chromium-blackened brass (diameter 58 mm). 23 The cell is sealed by Teflon and Viton rings. Approximately 20 mL of solution are required.…”

“…To reduce scattering intensity errors due to refractive index differences between the cylindrical outer glass wall and the surrounding air, a spherical lens is glued onto the outer cylinder. 23 The hemispherical detection geometry is formed by a horizontal rotational stage (Model 410, Huber, Germany) and a selfconstructed vertical hemicircular guide rail which leads the optical fiber (Quartz & Sílice, France). The scattering intensity measurements were done by photo counting (photon counter 6C1, EG&G Brookdeal).…”

Molecular Orientation and Deformation of Polymer Solutions under Shear: A Flow Light Scattering Study

“…Recently, interest in this approach was renewed and a few investigators have started to study flow light scattering of various polymer solutions in shear ,,− and elongational flows. Springer and co-workers have, to date, performed the most complete set of experiments on coil conformation by flow light scattering techniques.…”