In order to improve the thermal stability of be form of delta(e) that possesses nanoporous structure, benzoylation of the phenyl groups was adopted and performed by solution procedure or solid procedure. The solution procedure involves initial benzoylation of sPS in solution and then preparing delta(e) form by solvent induction of benzoylated sPS; the solid procedure means benzoylation of delta(e) form of sPS in solid state. Usual modifications of sPS by solution procedure greatly decrease the crystallinity of the nanoporous related delta(e) form. In this work, sPS can well maintain its crystallinity of delta(e) form after benzoylation by solution procedure, even when benzoylation degree reaches 20%. Thermally induced phase transition behaviors of corresponding delta(e) form were investigated by Differential scanning calorimeter and temperature-dependent X-ray diffraction analysis. The results show that the delta(e)-gamma transition temperature increases after benzoylation by both two procedures, indicating improved thermal stability of delta(e) form. The subsequent gamma-alpha transition and the melting of alpha form both shift to lower transition temperature. Meanwhile, the transition of delta(e) form to gamma form was prohibited by solution procedure contrast to solid procedure. (C) 2012 Elsevier Ltd. All rights reserved.