An explicit expression based on the configurational entropy model, the Flory-Huggins theory and Guggenheim's form of Debye-Mickel theory has been derived for predicting the glass transition temperatures (T-g) of binary semicrystalline polymer/salt complexes. The proposed configurational entropy (S-c) of polymer/salt systems consists of the disorientation entropy of polymer 1 (Sdiso-1), the dissociation entropy of salt (Sdiss-2), the mixing entropy (Smix-12) and the specific interaction entropy (Sspe-12). In particular, the effect of crystalline segments was accounted for by the current model. The prediction of the proposed T, model is in good agreement with experimental data. Our results demonstrate that the small change of the Tg in semicrystalline polymer/salt complexes compared to amorphous systems is mostly attributable to the reduced configurational entropy due to the presence of crystalline segments. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 793-798, 2009