Gas-separating properties of membranes based on star-shaped fullerene (C60)-containing polystyrenes

Based on regular star-shaped PSs differing in the structure of the branching center (one or two covalently bound fullerene C-60 molecules) and in the number of branchings (6 and 12), homogeneous gas-separation membranes have been produced. The transport behavior of the membranes with respect to several gases, such as H-2, He-2, N-2, CO, CO2, and CH4, has been studied by mass spectrometry. It has been found that the membranes prepared from six-arm PSs are characterized by a smaller density of macromolecular packing than the membranes obtained from 12-arm PCs and, consequently, they possess higher gas permeability. The starshaped PSs demonstrate a higher selectivity factor for separation of the O-2/N-2 gas pair compared to the corresponding characteristics of the linear PSs. The analysis of gas-separation characteristics by means of the Reitlinger-Robeson diagrams demonstrates that the transport behavior of star-shaped PSs qualitatively surpasses similar parameters of the known polymers in the separation of the CO/N-2 gas pair.