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Based on the Hadj-Romdhane–Danner model of the chromatographic process, the infinite dilution diffusion coefficients of n -hexane, n -heptane, n -octane and toluene in polyisobutylene (PIB) have been measured at temperatures in the range of 323.2–373.2 K by inverse gas chromatography (IGC). The measured infinite dilution diffusion coefficients for the toluene/PIB system were compared with the diffusivity data at finite concentration determined previously from NMR experimental method by using the Vrentas–Duda free volume theory. The good agreements indicate the IGC method studied in this work is reliable. Moreover, the correlations of the experimental data with the free volume equation were preformed. The correlated results show that the free volume theory is a quite good description of the relationship between the observed solvent diffusion coefficient and temperature.

The literature data of dilute solution viscosity for binary blend indicate that the intrinsic viscosity of binary polyblend can be obtained from the values of corresponding constituent polymers by using the weighted additive law. This law was also testified by measurement of CS/PEG polyblend in this work. On the basis of it, the α criterion of polymer–polymer miscibility determined by viscosity, proposed by Sun et al., is simplified. Since the revised criterion is a function of three variables: (1) the intrinsic viscosity for polymeric components (2) the weight fraction of polymeric components (3) the difference of the cross Huggins coefficient for polyblend and geometric average of Huggins coefficient for the constituent polymers, it is of more definite physical significance. Furthermore, it was proved that the revised criterion has the same judgment ability as that of the α criterion by using six binary blend systems, i.e. PVC/PMMA, PB(OH)/PBA, PB(OH)/PBMA, PVC/PiBMA, PMMA/PiBMA, PMMA/PiBMA, and three new binary blend systems measured in this work, i.e. PEG-6K/CS, PEG-10K/CS, PEG-20K/CS.