Polystyrene as an inert medium in the synthesis of the styrene/divinylbenzene/acrylonitrile copolymers

Samples of styrene/divinylbenzene/acrylonitrile macroporous copolymers were prepared, using polystyrene as inert medium. The initial viscosity average molecular weight of the polystyrene samples were: M?_v.i=87000, 98000, 117000 and 218000. The polystyrene samples with the initial molecular weights M?_v.i=87000 and M?_v.i=117000 were reused as inert media, for many times, until they lost their capacity to produce permanent porosity of the copolymers. The macroporous copolymers were characterized by their permanent porosity and volume swelling. If a polystyrene sample is used for many times, the molecular weight of the polystyrene removed (extracted) is gradually diminished and therefore the permanent porosity of the macroporous copolymers decreases step by step. The reasons responsible for this behaviour are:

• during the copolymerization process a polystyrene with a smaller molecular weight is formed.
• polystyrene parts of high molecular weights are included in the network structure of the macroporous copolymers.

The evidence for this was given by plotting the differential and integral molecular weight distribution curves for six samples of polystyrene.