Probing the Role of Side-Chain Interconnecting Groups in the Structural Hydrophobicity of Comblike Fluorinated Polystyrene by Solid-State NMR Spectroscopy

Abstract

In order to probe the role of side-chain interconnecting groups (-O-, -S-, and -SO2- linkages between the polystyrene (PST) main chain and fluorooctyl side chain) in the hydrophobicity of the comblike fluorinated polystyrenes, the molecular motion and structure of polymers are explored using the spin-lattice relaxation times (T1 and T1ρ) by solid-state (1)H and (19)F nuclear magnetic resonance spectroscopy. The chain-end motions of the polystyrene main chain and the fluorooctyl side chain are homogeneous, regardless of the interconnecting groups, which means that the chain-end motions of the main chain and the side chain maintain consistency, and these are irrelevant to each other. However, the local dynamic of the main chain shows the structural heterogeneity composed of the mobile and rigid regions, attributed to the rigidity of the side chain. The mobile dynamic portions of the main chain for PST-O and PST-S increase, and their rigid dynamic portions decrease as the temperature increases, whereas the ratio of structural heterogeneity for PST-SO2 is maintained despite increasing temperature. The activation energies (Ea) corresponding to the local motion of fluorooctyl side chains for PST-O and PST-S are drastically increased on the fast motion side compared to the slow motion side, suggesting the motional transformation of side chains for PST-O and PST-S from the small local motion into the large-scale movements related to a cooperative segmental motion when heated. Also, the local motion of the fluorooctyl side chain for PST-SO2 has similar Ea values on both sides, indicating that the relaxation time of PST-SO2 does not change with temperature. Therefore, PST-SO2 is structurally more stable than PST-O or PST-S, which can be attributed to the densely packed fluorooctyl side chain structure caused by the large dipole moment of the sulfone interconnecting group.

Confinement-Induced Change in Chain Topology of Ultrathin Polymer Fibers

“…However, the T 1 value is suitable for evaluating large-scale molecular motion at high temperatures because such motion become fast enough in this case to induce spin–lattice relaxation. That is to say, the scale of the molecular motion changes with an increase in the temperature . Typically, the activation energy as determined from T 1 for high temperatures is higher than that obtained from T 1 at low temperatures because large-scale molecular motion is restricted by chain entanglement and intermolecular interactions, in contrast to local motion, which occurs freely.…”

“…That is to say, the scale of the molecular motion changes with an increase in the temperature. 58 Typically, the activation energy as determined from T 1 for high temperatures is higher than that obtained from T 1 at low temperatures because large-scale molecular motion is restricted by chain entanglement and intermolecular interactions, in contrast to local motion, which occurs freely. Accordingly, considering that c-NF-70 exhibited an E a,high value twice as large as its E a,low value, large-scale reptation motion in c-NF-70 was severely constrained by the strong enthalpic structure.…”

Confinement of poly(allylamine) in Preyssler-type polyoxometalate and potassium ion framework for enhanced proton conductivity

“…This result suggests that side-chain mobility of III with the lowest average molecular weight of PAA (i.e., PAA1600) is faster than those of higher molecular weights. It has been reported that activation energies for the side-chain mobility of polymers in the solid state are at least 0.2 eV and sometimes larger than 1 eV depending on the backbone and side-chain structures 39,40 . Considering that the protonated amine group resides on the side-chain of PAA and the trend in activation energies of proton conduction (I: 0.16 eV ≈ II: 0.24 eV < III: 0.41 eV), it can be concluded that the side-chain mobility of PAA is crucial to the proton conduction in III.…”

Origins of the Gain in Hydrophobicity of Polystyrene Linked to the Addition of Tailored Fluorinated Oligo-Polystyrene Additives

“…In the previous three studies, a phase separation between the additive and the PS matrix was observed. In other studies, 14,15 PS was chemically modified by synthetizing comb-like fluorinated PS (Figure 1d), reaching a sCAW of 123°. Diblock copolymers of PS and PS modified with a side-chain group of polyoxyethylene-polytetrafluoroethylene were also synthetized, 16,17 reaching a maximum sCAW of 113°with 100 wt % of the additive, shown in Figure 1e.…”