Birefringence multicomponent systems

The sonic technique suffers from one of the same difficulties as the birefringence method in that only an average orientation of the total system is obtained. Thus, if one has a multicomponent system (e.g. semicrystalline, block copolymer. etc.X one cannot separate component orientation by this technique alone. It is noteworthy that the orientation measured by the sonic method can be correlated directly with birefringence data on the same material.This ease of correlation has been suggested to lead to values of the intrinsic birefringence by extrapolation of the sonic data to perfect orientation. 

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