DETERMINATION OF INTRINSIC BIREFRINGENCE OF SMECTIC PHASE IN ISOTACTIC POLYPROPYLENE

When isotactic polypropylene is quenched at 0 degrees C from the molte n state, a biphasic material, amorphous-smectic, is obtained. The smec tic phase has an intermediate order between the amorphous and the crys talline. In this study the intrinsic birefringence of the smectic phas e was determined. Tapes with different draw ratio were prepared at roo m temperature, at which the smectic phase does not transform into the crystalline phase. The amount of the smectic phase was determined with measurements of density and sorption of vapors of dichloromethane. Th e value of the intrinsic birefringence for the smectic phase is: Delta degrees n(sm) = 40 . 10(-3). This value is in good agreement with the values proposed by Samuels for the intrinsic birefringence of the amo rphous and the crystalline phases. (C) 1996 John Wiley & Sons, Inc.