Miwa Yohei, Hasegawa Koki, Udagawa Taro, Shinke Yu, Kutsumizu Shoichi
Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan.
PRESTO, Japan Science and Technology Agency, Japan.
Phys Chem Chem Phys. 2022 Jul 21;24(28):17042-17049. doi: 10.1039/d2cp01159j.
The effects of cations, Li, Na, and Cs, on the structure of ionic aggregates and network rearrangement in carboxylated polyisoprene (PI) ionomers were studied. We found that network rearrangement interaggregate hopping of metal carboxylates is improved with a decrease in cation size, even though density functional theory (DFT) calculation indicated the increase in the attractive interaction between metal carboxylates. At the same time, we also found that as the size of the cation decreases, the inclusion of the PI segment in the ionic aggregate increases. The DFT calculation suggested the cation-π interaction between the cation and double bonds in the PI segment as the cause for the inclusion. The inclusion of the PI segment with a low glass transition temperature () plasticizes the ionic aggregate and would sterically hinder the attractive interaction between metal carboxylates. In fact, the electron spin resonance measurement revealed a decrease in the of the ionic aggregate with a decrease in cation size. Based on our findings, we proposed that the inclusion of PI segments in the ionic aggregate is the possible cause for the enhancement of network rearrangement in the carboxylated PI ionomers with a decrease in the cation size.
研究了阳离子Li、Na和Cs对羧化聚异戊二烯（PI）离聚物中离子聚集体结构和网络重排的影响。我们发现，尽管密度泛函理论（DFT）计算表明金属羧酸盐之间的吸引相互作用增加，但随着阳离子尺寸的减小，金属羧酸盐的网络重排和聚集体间跳跃得到改善。同时，我们还发现，随着阳离子尺寸的减小，离子聚集体中PI链段的包含量增加。DFT计算表明阳离子与PI链段中的双键之间存在阳离子-π相互作用是导致这种包含的原因。具有低玻璃化转变温度（）的PI链段的包含使离子聚集体增塑，并会在空间上阻碍金属羧酸盐之间的吸引相互作用。事实上，电子自旋共振测量表明，随着阳离子尺寸的减小，离子聚集体的减小。基于我们的发现，我们提出离子聚集体中PI链段的包含可能是羧化PI离聚物中随着阳离子尺寸减小网络重排增强的原因。
