Department of Macromolecular Science and Engineering, Sakyo-ku, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
Research and Services Division of Materials Data and Integrated System, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
ACS Macro Lett. 2022 Mar 15;11(3):362-367. doi: 10.1021/acsmacrolett.1c00801. Epub 2022 Feb 25.
Polyrotaxane (PR) gels with low ring densities have figure-of-eight cross links that can slide along network strands. The slidable cross links have a unique ability to increase the network strand length between adjacent cross links in the loading direction via chain supply from the stress-free direction, thereby enhancing the ultimate elongation (λ) of the gels. We reveal that this enhancement of λ due to the slidable cross links is pronounced specifically in uniaxial stretching, while it is considerably modest in biaxial stretching. The sensitivity of λ to loading axiality becomes larger as the ring densities decrease. The corresponding difference in λ is markedly larger for the PR gels with low ring densities than that for the networks with fixed cross links. The exceptional sensitivity of λ to loading axiality unveils a previously unidentified aspect of the chain-supply mechanism based on slidable cross links.
聚轮烷（PR）凝胶的环密度较低，具有可沿网络链滑动的 8 字形交联。可滑动的交联具有独特的能力，可通过从无应力方向供应链来增加相邻交联之间的网络链长度，从而提高凝胶的极限伸长率（λ）。我们揭示了这种由于可滑动交联而导致的 λ 的增强在单轴拉伸中特别明显，而在双轴拉伸中则相当适度。随着环密度的降低，λ 对加载轴性的敏感性增大。对于低环密度的 PR 凝胶，λ 的对应差异明显大于具有固定交联的网络。λ 对加载轴性的异常敏感性揭示了基于可滑动交联的链供应机制的一个以前未被识别的方面。
