Sub-T-g annealing of the clathrate delta form of syndiotactic polystyrene

Amorphous films of syndiotactic polystyrene were crystallized in dichlorome thane, to obtain samples in the clathrate delta form; successively the samp les were either annealed at temperatures below the glass transition tempera ture (T-g) or extracted with acetone. The samples obtained show, in the X-r ay analysis, crystalline structures tending toward the "emptied" delta form , free of solvent molecules, as already described for sPS. The study of the transport properties, diffusion and sorption of dichloromethane vapor, sho ws that the annealed samples are characterized by a slightly lower diffusio n coefficient, but much higher sorption at low activity of the vapour. This high sorption is explained by the penetration of solvent molecules both in to the amorphous and the "emptied" crystalline phase, producing again the c lathrate form at low vapour activity. The high sorption capability makes th ese samples promising as sorption media to remove traces of polluting chlor inated solvents both in the liquid and in the vapour phase.