Crystallization from the amorphous form of the nanoporous epsilon form of syndiotactic polystyrene

The recently discovered channel-shaped nanoporous epsilon crystalline phase of syndiotactic polystyrene (s-PS) is generally obtained by a chloroform-induced recrystallization of samples exhibiting the helical gamma crystalline phase, followed by chloroform desorption in suitable conditions. This nanoporous e crystalline phase can be also obtained by crystallization of amorphous samples as induced by the same chloroform sorption-desorption procedure. This procedure, which does not affect b form samples, when applied to samples exhibiting the trans-planar a phase instead leads to a recrystallization into the cavity-shaped nanoporous d phase. Both nanoporous crystalline phases (d and e) are obtained, by this chloroform treatment on uniaxially stretched amorphous films. In particular, polarized FTIR microscopy clearly shows that d and e crystalline phases prevail in central and lateral film regions, respectively. In fact, in the film central regions, higher polymer draw ratios are reached that lead to higher degrees of trans-planar crystallinity, whose chloroform induced crystallization leads to d phase formation.