Effects of post-crosslinking of macroreticular styrene-divinylbenzene copolymers on their morphology

We performed a detailed comparison of properties of two different styrenic polymers containing divinylbenzene as the crosslinker before and after the introduction of the additional crosslinks by Friedel-Craft's reaction of the residual double bonds. For the polymer characterization was used a wide selection of methods, including nitrogen adsorption/desorption, inverse steric exclusion chromatography, MAS NMR and AFM. The residual double bonds are quite probably located in the dense cores of the microgel domains where steric hindrances prevented them to react during the polymerization. Reinforcement of the cores of polymer microgel domains by transformation of the residual double bonds into additional crosslinks by the Friedel-Craft's reaction results then in greater stability of the already existing pores rather than in creation of new pores by incomplete collapse of swollen polymer gel.