Stretch-Induced Solid-to-Solid Phase Transition in Semicrystalline Polymer: Crucial Role of Crystallographic Slipping

Semicrystalline polymers can undergo solid-to-solid phase transition through conformational change, crystallographic slipping, or melt-recrystallization upon stretching. However, crystallographic slipping often couples with the crystal melt-recrystallization process, and its crucial role in solid-to-solid phase transition has not been well understood. Herein, we chose <i>trans</i>-1,4-polybutadiene (<i>t</i>PBD) as a model polymorphic polymer and investigated its crystal phase transition and lamellar structural evolutions during stretching at various temperatures. <i>t</i>PBD retains monoclinic and hexagonal phases upon stretching at low (≤20 °C) and high (e.g., 70 °C) temperatures, respectively, which is consistent with the polymorphic structures obtained during quiescent crystallization. Interestingly, upon stretching at the intermediate temperatures of 25-50 °C, the monoclinic-to-hexagonal phase transition proceeds through a solid-to-solid pathway, as dominated by crystallographic slipping. The stretch-induced formation of the hexagonal phase is favored at higher strains and elevated temperatures. This study shed light on the crucial role of crystallographic slipping in the solid-to-solid phase transition of semicrystalline polymers.