Theory of Orientation and Double Refraction in Polymers

Abstract

Orientation and birefringence in linearly oriented amorphous polymers are discussed with particular emphasis on polystyrene type chains. A system of completely uncoiled parallel zigzag chains is defined as 100 percent orientation. The variation of birefringence with orientation is assumed to follow the same expression as that for the variation of polarization anisotropy with extension for a single random coil chain. With these assumptions and reasonable models for the completely uncoiled polystyrene chain it is possible to express any given birefringence as a percentage orientation. Methods are developed for the experimental determination of the birefringence at a particular point in an oriented monofilament instead of the usual determination of an average birefringence through the monofilament. The application of these methods to actual examples leads to reasonable values of the orientation.

Polymer applications

“…the mean orientation of monomer units. The relation between orientation and birefringence was known from early studies of polystyrene filaments which described both the theory and measurement [21,23]. They showed that the orientation was greater at the surface than in the core.…”

“…177 It may be difficult to know which fringe is correct if the dispersion of the birefringence of the fiber is different to that of the compensator. A useful trick is to cut a wedge at the end of the fiber and count the number of fringes along the wedge, which is the number of full orders of path difference [21]. The additional partial order is measured with a compensator [22] (Section 3.4.3).…”

Shear Thickening in Dilute Polymer Solutions: Transient Analysis

“…The polarizability difference, ða 1 À a 2 Þ 1 ¼ À5:49 Â 10 À24 cm 3 =molecule, is assigned the value calculated by Kishbaugh and McHugh (Kishbaugh, 1992;Kishbaugh and McHugh, 1993b) using the method of Gurnee (1954). This contribution to the birefringent signal is always negative in sign.…”

“…This last quantity was estimated by Kishbaugh and McHugh as À1:25 Â 10 À42 cm 3 =molecule using the method of Gurnee (1954). Since trc c 1 is always greater than three, this contribution to the dichroic signal is always negative in sign.…”

Relation between Molecular Conformation and Birefringence of Common Olefinic and Vinyl Polymers.

“…7(1993) could not reflect the chain conformation which is allowed in solid state for both crystalline and amorphous poly mers. Therefore, when such an anisotropic group as phenyl was introduced into polymer, its contribution to the birefringence was quite different depending on the alignment of the benzene ring (22).…”