Abstract:Polymers in ionic liquids (ILs) are a fascinating class of materials that exhibit unusual behavior in comparison to more traditional polymer solutions. Previous work characterizing the lower critical solution temperature (LCST) phase behavior of poly(benzyl methacrylate) (PBnMA)/IL mixtures demonstrated that the second virial coefficient is consistently positive, even at temperatures above the observed phase separation boundary, and that the critical composition is shifted strongly toward polymerrich compositi… Show more
“…The calculated χ eff using eq for G solutions at 40 °C, close to T θ at C Cl = 1.0 M, is nearly independent of molecular weight but clearly increases from 0.50 to 0.56 as c increases from 4.4 to 15 wt %, as shown in Figure a. Although the Flory−Huggins theory assumes χ is independent of polymer concentration, the polymer concentration dependence of χ has been reported for various polymer solutions, and the dependence intensifies as the temperature approaches the θ condition. ,,− It is noted that the RPA analysis assumes spatial uniformity and randomness in local concentration, and eq is usually employed to describe semidilute polymer solutions. Therefore, we classified χ eff measured below and above c * in Figure a, yet the concentration dependence of χ eff is consistently observed under our experimental conditions. 8 (a) Effective interaction parameter, χ eff , of G -102 (red), G -80 (orange), G -50 (green), and G -31 (blue) solutions as a function of polymer concentration at 40 °C and C Cl = 1.0 M determined by random phase approximation (RPA).…”
Section: Discussionmentioning
confidence: 89%
“…Figure c displays 1/ I (0) vs 1/ T for G -102 solutions with various polymer concentrations at C Cl = 1.0 M, demonstrating the linear relationship between 1/ I (0) and 1/ T . As temperature approaches the spinodal temperature ( T s ), I (0) becomes divergent as 1/ I (0) ∼ (1/ T s − 1/ T ). ,,, Therefore, T s is determined by linear extrapolation to the x -intercept of 1/ I (0), leading to T s = 3, 20, 26, 23, 17, and 5 °C for 1, 2.5, 4.5, 8, 11, and 15 wt % G -102 solutions, respectively, at C Cl = 1.0 M (also see Figure S18 for the other G solutions). In the Section , T s obtained from all G polymers as a function of c and C Cl are used to construct the spinodal curves.…”
Section: Resultsmentioning
confidence: 99%
“…The enthalpic contribution mainly originated from the monomer−monomer interaction, and it is expected that the increase as a function of polymer concentration is insignificant. However, it is noted that other possibilities to affect A and B as a function of polymer concentration cannot be ruled out because the concentration dependence of χ eff has been widely observed in other systems. ,,− …”
Liquid−liquid phase separation (LLPS), driven by specific associative interactions, plays a pivotal role in the formation of molecular condensates. Previously, our research [Oh, S.-H. et al. Macromolecules 2023, 56, 3989−3999] unveiled LLPS in aqueous solutions of guanidinium-containing polymers induced by monovalent salt addition, displaying upper critical solution temperature (UCST) phase behavior. This behavior is mainly attributed to the face-to-face π−π stacking of guanidinium groups when the Coulombic repulsion is attenuated. In this work, we characterize the UCST behavior using transmittance, static light scattering, and small-angle neutron scattering, elucidating the pertinent thermodynamic parameters. The cloud point and spinodal temperatures gradually increase as the concentration of the counteranion increases across a wide temperature range between 0 and 100 °C. Also, theta temperature (T θ ) and the effective interaction parameter (χ eff ) for solutions change in a quantitative manner with the anion concentration. The entropic and enthalpic contributions to χ eff are found to decrease and increase with the anion concentration, respectively. This increase in the enthalpic penalty between the monomer and the solvent is attributed to the attractive monomer−monomer interactions via π−π interaction of guanidinium pairs at higher anion concentrations, inducing phase separation. Our findings provide thermodynamic insights into the significant role of associative interaction for molecular condensations in aqueous media and the molecular mechanisms driving UCST phase behavior.
“…The calculated χ eff using eq for G solutions at 40 °C, close to T θ at C Cl = 1.0 M, is nearly independent of molecular weight but clearly increases from 0.50 to 0.56 as c increases from 4.4 to 15 wt %, as shown in Figure a. Although the Flory−Huggins theory assumes χ is independent of polymer concentration, the polymer concentration dependence of χ has been reported for various polymer solutions, and the dependence intensifies as the temperature approaches the θ condition. ,,− It is noted that the RPA analysis assumes spatial uniformity and randomness in local concentration, and eq is usually employed to describe semidilute polymer solutions. Therefore, we classified χ eff measured below and above c * in Figure a, yet the concentration dependence of χ eff is consistently observed under our experimental conditions. 8 (a) Effective interaction parameter, χ eff , of G -102 (red), G -80 (orange), G -50 (green), and G -31 (blue) solutions as a function of polymer concentration at 40 °C and C Cl = 1.0 M determined by random phase approximation (RPA).…”
Section: Discussionmentioning
confidence: 89%
“…Figure c displays 1/ I (0) vs 1/ T for G -102 solutions with various polymer concentrations at C Cl = 1.0 M, demonstrating the linear relationship between 1/ I (0) and 1/ T . As temperature approaches the spinodal temperature ( T s ), I (0) becomes divergent as 1/ I (0) ∼ (1/ T s − 1/ T ). ,,, Therefore, T s is determined by linear extrapolation to the x -intercept of 1/ I (0), leading to T s = 3, 20, 26, 23, 17, and 5 °C for 1, 2.5, 4.5, 8, 11, and 15 wt % G -102 solutions, respectively, at C Cl = 1.0 M (also see Figure S18 for the other G solutions). In the Section , T s obtained from all G polymers as a function of c and C Cl are used to construct the spinodal curves.…”
Section: Resultsmentioning
confidence: 99%
“…The enthalpic contribution mainly originated from the monomer−monomer interaction, and it is expected that the increase as a function of polymer concentration is insignificant. However, it is noted that other possibilities to affect A and B as a function of polymer concentration cannot be ruled out because the concentration dependence of χ eff has been widely observed in other systems. ,,− …”
Liquid−liquid phase separation (LLPS), driven by specific associative interactions, plays a pivotal role in the formation of molecular condensates. Previously, our research [Oh, S.-H. et al. Macromolecules 2023, 56, 3989−3999] unveiled LLPS in aqueous solutions of guanidinium-containing polymers induced by monovalent salt addition, displaying upper critical solution temperature (UCST) phase behavior. This behavior is mainly attributed to the face-to-face π−π stacking of guanidinium groups when the Coulombic repulsion is attenuated. In this work, we characterize the UCST behavior using transmittance, static light scattering, and small-angle neutron scattering, elucidating the pertinent thermodynamic parameters. The cloud point and spinodal temperatures gradually increase as the concentration of the counteranion increases across a wide temperature range between 0 and 100 °C. Also, theta temperature (T θ ) and the effective interaction parameter (χ eff ) for solutions change in a quantitative manner with the anion concentration. The entropic and enthalpic contributions to χ eff are found to decrease and increase with the anion concentration, respectively. This increase in the enthalpic penalty between the monomer and the solvent is attributed to the attractive monomer−monomer interactions via π−π interaction of guanidinium pairs at higher anion concentrations, inducing phase separation. Our findings provide thermodynamic insights into the significant role of associative interaction for molecular condensations in aqueous media and the molecular mechanisms driving UCST phase behavior.
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