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The molecular motion of imidazole (Im) in proton-conducting polyacrylic acid (PAA)/Im composite materials (PAA/xIm, where x represents the number of moles of Im per mole of the carboxyl group of PAA) was investigated using solid-state 2H NMR. For the 2H NMR analysis of polymers in which multiple constituents with different kinetic states coexist, we propose the simultaneous analysis of two 2H NMR spectra observed by the quadruple echo method using different echo intervals. The 2H NMR spectra were analyzed by superimposing simulated spectra with different jumping rates of 180° flip and isotropic rotation of Im. For PAA/0.5Im-d3, Im undergoes 180° flip below 343 K and isotropic rotation above 363 K. For PAA/1.0Im-d3, Im undergoes 180° flip below 323 K and isotropic rotation above 363 K. In the temperature range of 333–343 K, Im undergoing 180° flip and isotropic rotation coexist in PAA/1.0Im-d3. The distributions of the jumping rates of 180° flip and isotropic rotation of Im were obtained. The increase in the amount of Im enhances the jumping rate of the isotropic rotation of Im and the proton conductivity of PAA/xIm at high temperatures. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS) elastomers with varying crosslink densities were synthesized using prepolymers with different molecular weights. The association constants (Ka) between a pyrene derivative (PySi) and naphthalenediimide derivative (NDISi) were measured in linear PDMS and PDMS elastomers. The shape of the absorption peak in the charge‐transfer (CT) band and the association constants were nearly independent of the crosslink density. Moreover, the temperature dependence of the association constants demonstrated consistent behavior across all PDMS media. This indicates that the structure of the CT complex and the Gibbs free energy of its formation in the PDMS are unaffected by the crosslink density, providing insights into the design of supramolecular architectures formed by the CT complex in a PDMS network. [ABSTRACT FROM AUTHOR]

Fluorocarbon gases are regarded as one of the largest contributors to serious environmental problems such as ozone‐depletion and global warming, and thus, the development of reclamation technologies is in great demand for reducing emission of such harmful compounds. So far, porous materials such as zeolites, activated carbons, and metal‐organic frameworks (MOFs) have been examined as solid‐state absorbents for fluorocarbon gases. However, such porous materials often suffer from a lack of size‐selectivity in fluorocarbon gas uptakes due to the large‐sized cavities (>1 nm). Herein, it is reported that macrocyclic pillar[n]quinones (P[n]Q, n = 5 or 6) in crystalline state show size‐selective uptake for fluorocarbon gases owing to their molecular‐scale cavities (<1 nm). The P[n]Q also show uptake behaviors for volatile halogenated organic compounds (VHOCs), which are highly toxic. Interestingly, the volatilities of VHOCs within the 1D channels of P[5]Q are drastically reduced compared with those of the bulk VHOC solvents. Experimental results and computational analyses revealed that the excellent storage abilities of the crystalline P[n]Q are a synergic result of their electron‐deficient macrocyclic scaffolds and the basic carbonyl oxygen atoms on their rims. [ABSTRACT FROM AUTHOR]