Methods for assessment of uniaxial chain orientation

There are several methods which are commonly used for the determination of chain orientation e.g. measurement of in-plane birefringence, wide-angle X-ray diffraction, small-angle X-ray diffraction, infrared spectroscopy and sonic modulus measurements. The first four are briefly presented in this section. 

Recommended reading for a more in-depth understanding is given at the end of the chapter. 

We deal in this section only with the simplest case, namely uniaxial orientation (Fig. 9.7). There is only one unique direction, the z(3) direction. Orientation exists only in the x, z) and (y, z) planes. The uniaxial system appears to be isotropic in the x, y) plane. 

Birefringence measurements are classical. The Hermans orientation function (/) is proportional to the birefringence An)  

If orientation is uniaxial and both form and deformation birefringence can be neglected, eq. (9.26) can be rewritten  

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