2026-09-18 九州大学
熱硬化性樹脂の硬化過程における分子描像。（左から）反応前の液体状態、ゲル化前での緻密化状態、ゲル化状態、ゲル化後での拘束状態を示す。図中の点線は体積収縮前の体積に対応し、ポストゲル拘束状態における矢印は分子相関を示す。
＜関連情報＞
- https://www.kyushu-u.ac.jp/ja/researches/view/1567
- https://www.nature.com/articles/s43246-026-01353-0
架橋ポリマーネットワークにおけるゲル化過程における巨視的緻密化と分子構造変化の分離 Decoupling between macroscopic densification and molecular structural evolution across gelation in cross-linked polymer networks
Atsuomi Shundo, Aoi Kontani, Atsushi Tokunaga, Tsuyoshi Miyashita, Satoru Yamamoto & Keiji Tanaka
Communications Materials Published:18 September 2026
DOI:https://doi.org/10.1038/s43246-026-01353-0
Abstract
Cure-induced shrinkage in thermosetting polymers is generally assumed to reflect progressive densification during network formation. Here, we show that this assumption breaks down at gelation, which marks a transition in structural evolution. Using a model epoxy system, direct shrinkage measurements, wide-angle X-ray scattering, and molecular dynamics (MD) simulations are combined to link macroscopic densification with molecular-scale structural evolution. We find that macroscopic densification occurs predominantly before the gel point and becomes strongly suppressed after the formation of a percolated network. Conversely, characteristic intermolecular distances associated with phenyl-rich and hydroxyl-containing correlations continue to increase, with narrowing distributions, indicating constrained local reorganization within the network. MD simulations reveal that this behavior is accompanied by coarsening of free space, with both its fraction and characteristic size increasing despite an approximately constant density. These results establish gelation as a fundamental boundary separating distinct regimes of structural evolution, providing new principles for controlling shrinkage and internal stress.
