Associate Researcher Hang Guo (currently Associate Professor at Xi’an Jiaotong University), Professor Kunpeng Cui, and Researcher Hongjun Zhang from the State Key Laboratory of Nuclear Detection and Electronics have systematically investigated the evolution of free volume voids in highly oriented isotactic polypropylene elastomers (HEPP) during tensile deformation, using an in-situ ultra-high count rate positron annihilation lifetime spectroscopy (PALS) technique developed through collaborative research.
By combining experimental results from in-situ synchrotron small-angle X-ray scattering (SAXS), the research team discovered that stretching induces the growth, coalescence, and redistribution of sub-nanometer-scale free volume voids within the interlamellar amorphous phase. They further proposed a reasonable physical model to explain this evolution process: stress-induced microphase separation in the interlamellar amorphous regions. This study was published in Macromolecules, a top-tier journal in the field of polymer science, and was selected as the front cover article for that issue.
This research considered the real-time evolution of free volume within the interlamellar amorphous phase under uniaxial tensile deformation, clarifying the mechanism of instability. In future work, the research team will focus on the structural evolution of HEPP and similar model semicrystalline polymers under various loading modes, including shear and combined shear-tensile loading, aiming to develop a comprehensive understanding of the deformation mechanisms at the lamellar cluster scale.
This work was supported by the National Natural Science Foundation of China (Grant Nos. 52303048, 12275270, 11975225) and the National Key R&D Program of China (Grant Nos. 2020YFA0405800, 2019YFA0210000).
Guo H, Luo M, Dong Y, et al. Evolution of Free-Volume Pores during Stretch-Induced Instability of the Interlamellar Amorphous Phase in Semicrystalline Polymers[J]. Macromolecules, 2025, 58(9),4645–4654
Paper link：https://pubs.acs.org/doi/10.1021/acs.macromol.4c02851
