biostudies-literatureAoki KIketani Science and Technology FoundationTokai Foundation for TechnologyAsahi Glass FoundationFoundation of Kinoshita Memorial Enterprise10396-10401https://www.ebi.ac.uk/biostudies/studies/S-EPMC10683071biostudies-literatureUnknown14(46)Sol-gel transitions of polymers are pivotal phenomena in material science, yet the critical phenomenon of structure during gelation has remained unclear. Here, we investigated the sol-gel transition of a fluorous polymer, poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene), in a blend of two ionic liquids. This system features a quite high amount of cross-linker and binding sites with ion-dipole interactions between the cation and C-F dipoles, thereby facilitating easy exchange of the cross-links. Changing the mixing ratio of the two ionic liquids enabled tuning the ion-dipole interactions and inducing sol-gel transition. Notably, the correlation length and molar mass, obtained by small-angle X-ray scattering, diverged at the gelation point. Moreover, the derived critical exponents (ν = 0.85 ± 0.05) aligns remarkably well with the prediction from percolation theory (ν = 0.88). To our knowledge, this is the first report on the evident divergence during polymeric gelation by small-angle scattering and the verification of the critical exponents of the percolation theory.The journal of physical chemistry lettersPolymeric Sol-Gel Transition with the Diverging Correlation Length Verified by Small-Angle X-ray Scattering.PMC106830710341186-ATakahashi RAoki KSugawara-Narutaki AfalsePolymeric Sol-Gel Transition with the Diverging Correlation Length Verified by Small-Angle X-ray Scattering.Sol-gel transitions of polymers are pivotal phenomena in material science, yet the critical phenomenon of structure during gelation has remained unclear. Here, we investigated the sol-gel transition of a fluorous polymer, poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene), in a blend of two ionic liquids. This system features a quite high amount of cross-linker and binding sites with ion-dipole interactions between the cation and C-F dipoles, thereby facilitating easy exchange of the cross-links. Changing the mixing ratio of the two ionic liquids enabled tuning the ion-dipole interactions and inducing sol-gel transition. Notably, the correlation length and molar mass, obtained by small-angle X-ray scattering, diverged at the gelation point. Moreover, the derived critical exponents (ν = 0.85 ± 0.05) aligns remarkably well with the prediction from percolation theory (ν = 0.88). To our knowledge, this is the first report on the evident divergence during polymeric gelation by small-angle scattering and the verification of the critical exponents of the percolation theory.2023-01-01T00:00:00Z2023 Nov2025-04-18T13:12:46.491Z2025-04-06T22:45:27.72ZS-EPMC106830713795563010.1021/acs.jpclett.3c02631