The recently discovered channel-shaped nanoporous epsilon crystalline form of syndiotactic polystyrene (s-PS) is generally obtained by a chloroform-induced recrystallization of samples exhibiting the helical gamma crystalline form, followed by chloroform desorption in suitable conditions. This nanoporous epsilon crystalline form can be also obtained by crystallization of amorphous samples as induced by the same chloroform sorption-desorption procedure. This procedure, which does not affect beta form samples, when applied to samples exhibiting the trans-planar a form instead leads to a recrystallization into the cavity-shaped nanoporous delta form. Both nanoporous crystalline forms (delta and epsilon) are obtained, by this chloroform treatment on uniaxially stretched amorphous films. In particular, polarized FTIR microscopy clearly shows that delta and epsilon crystalline forms 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 delta form formation. (C) 2010 Elsevier Ltd. All rights reserved.