The sorption properties of atactic polypropylene (APP) and isotactic polypropylene (IPP) were studied by equilibrium sorption of various organic solvents. The variation of the Flory‐Huggins interaction parameter χ for the APP‐CCl 4 system at 25°C was expressed as a function of the volume fraction v 2 of polymer by the relation: x = 0.113 exp {1.879 v 2 }. The average molecular weight M c of the polymer chains between successive crystallites for IPP subjected to different thermal treatments was calculated to be 250 to 350 by the equation of Flory and Rehner. From the variation of M c with solvent concentration, we estimated the number fraction of polymer chains actually contributing to elastic deformation. The clustering function for solvent in the polymer calculated by the method of Zimm and Lundberg decreased linearly from a positive value to −1 with increasing solvent concentration. Clustering of solvent molecules was found to occur more easily in APP than in IPP.
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Ochiai et al. (1971) studied this question.
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