Sub-T<INF>g</INF> annealing of the clathrate δ form of syndiotactic polystyrene

Amorphous films of syndiotactic polystyrene were crystallized in dichloromethane, to obtain samples in the clathrate δ form; successively the samples were either annealed at temperatures below the glass transition temperature (T<INF>g</INF>) or extracted with acetone. The samples obtained show, in the X-ray analysis, crystalline structures tending toward the “emptied” δ form, free of solvent molecules, as already described for sPS. The study of the transport properties, diffusion and sorption of dichloromethane vapor, shows that the annealed samples are characterized by a slightly lower diffusion coefficient, but much higher sorption at low activity of the vapour. This high sorption is explained by the penetration of solvent molecules both into the amorphous and the “emptied” crystalline phase, producing again the clathrate form at low vapour activity. The high sorption capability makes these samples promising as sorption media to remove traces of polluting chlorinated solvents both in the liquid and in the vapour phase.