Thermal effects on the strain-induced structural transition from beta-form to alpha-form crystals of syndiotactic polystyrene (sPS) were investigated by changing the stretching temperature and the annealing temperature. When sPS was stretched at lower temperature (near the glass transition temperature (Tg) of sPS (similar to 130 degrees C)), the crystalline structural transition was incomplete, producing fragmented beta-form and mesomorphic alpha-form crystals. Stretching at higher temperature facilitated the crystalline structural transition from beta to a. For the sPS specimen stretched at 130 degrees C, the beta-form crystals broke into small pieces, simultaneously creating mesomorphic alpha-form crystals. After annealing, the fragmented beta-form crystals and the mesomorphic alpha-form crystals were reorganized to become complete crystals. The reorganization became more pronounced as the annealing temperature increased. The main role of the mechanical strain and the heat, therefore, could be the destruction of beta-form crystals to produce fragmented beta-form crystals and mesomorphic alpha-form crystals, and the formation of complete crystals, respectively. (C) 2017 Elsevier Ltd. All rights reserved.