ε Form Gels and Aerogels of Syndiotactic Polystyrene

Mixtures of two solvents allow obtaining stable physical gels of syndiotactic polystyrene (s-PS), whose physical knots are for the first time constituted by ε cocrystals. These ε gels, by simple scCO2 extraction procedures, lead to aerogels only exhibiting the nanoporous-crystalline ε form, with a degree of crystallinity higher than 45%. This preparationprocedure is the first one leading to pure ε form aerogels. Although the BET surface areas for ε aerogels (exhibiting crystalline nanochannels) are much lower than for δ form aerogels (exhibiting isolated crystalline nanocavities), the uptake of long organic molecules is definitely higher for ε aerogels, with differences becoming very high at low guest pressures. Moreover, for all guests, pure ε aerogels present uptakes significantly higher than the previously known ε + γ aerogels.