• DOI:10.1073/pnas.2015672117
• Corpus ID: 220514532

Entropy-controlled cross-linking in linker-mediated vitrimers

@article{Lei2020EntropycontrolledCI,
  title={Entropy-controlled cross-linking in linker-mediated vitrimers},
  author={Qun-li Lei and Xiuyang Xia and Juan Yang and Massimo Pica Ciamarra and Ran Ni},
  journal={Proceedings of the National Academy of Sciences},
  year={2020},
  volume={117},
  pages={27111 - 27115}
}

• Qun-li Lei, Xiuyang Xia, +2 authors R. Ni
• Published 14 July 2020
• Materials Science, Biology
• Proceedings of the National Academy of Sciences

Significance The recently developed linker-mediated vitrimers based on metathesis reactions offer new possibilities of processing cross-linked polymers with high mechanical performance in industry, while the design principle remains unknown. Here we propose a theoretical framework for describing the system of linker-mediated vitrimers, in which entropy is found to play a dictating role. Our mean field theory agrees quantitatively with computer simulations, and provides guidelines for the rational design of the linker-mediated vitrimers with desired properties. Recently developed linker-mediated vitrimers based on metathesis of dioxaborolanes with various commercially available polymers have shown both good processability and outstanding performance, such as mechanical, thermal, and chemical resistance, suggesting new ways of processing cross-linked polymers in industry, of which the design principle remains unknown [M. Röttger et al., Science 356, 62–65 (2017)]. Here we formulate a theoretical framework to elucidate the phase behavior of the linker-mediated vitrimers, in which entropy plays a governing role. We find that, with increasing the linker concentration, vitrimers undergo a reentrant gel–sol transition, which explains a recent experiment [S. Wu, H. Yang, S. Huang, Q. Chen, Macromolecules 53, 1180–1190 (2020)]. More intriguingly, at the low temperature limit, the linker concentration still determines the cross-linking degree of the vitrimers, which originates from the competition between the conformational entropy of polymers and the translational entropy of linkers. Our theoretical predictions agree quantitatively with computer simulations, and offer guidelines in understanding and controlling the properties of this newly developed vitrimer system.