With the guidance of Prof. Li and Assistant researcher Chen the Stretch-induced Crystallization and Phase Transitions of Poly(dimethylsiloxane) at Low Temperatures: an in situ Synchrotron Radiation Wide-angle X-ray Scattering Study is studied by doctor Jingyun Zhao et al. The related work has been published in Macromolecules.
Stretch-induced crystallization (SIC) and phase transitions of poly(dimethylsiloxane) (PDMS) have been studied with the in situ synchrotron radiation wide-angle X-ray scattering technique (WAXS) during tensile deformation at temperatures ranging from -45 to -65 oC. The phase transitions during tensile deformation go through different processes at different temperature regions, where four phases are involved in, namely oriented amorphous (OA), mesophase, α form, and β form crystals. We found that SIC of α form can proceed via two different multi-stage ordering processes with either mesophase or β form as the structural intermediate. Further cyclic tensile experiments demonstrate that transition from β to α form is a reversible process controlled by stress, which is attributed to the different helical pitches in β and α forms. A non-equilibrium phase diagram of SIC and phase transitions are constructed in strain-temperature space, which is of great significance for practical applications of PDMS at low temperature.
This work is supported by the the National Natural Science Foundation of China (51633009, 51790500, 51573177 and 51473151)and joint fund of the National Natural Science Foundation of China and China Academy of Engineering Physics (U1530114). The experiments are carried out in Shanghai Synchrotron Radiation Facility (SSRF).
Related links: https://pubs.acs.org/doi/abs/10.1021/acs.macromol.8b01872
