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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]

Poly(ethylene oxide)s (PEOs) are useful polymers with good water solubility, biological compatibility, and commercial availability. PEOs with various end groups were threaded into pillar[5]arene rings in a mixture of water and methanol to afford pseudopolyrotaxanes. Corresponding polyrotaxanes were also constructed by capping COOH‐terminated pseudopolyrotaxanes with bulky amines, in which multiple hydrogen bonds involving the pillar[5]arene OH groups were critically important to prevent dethreading. The number of threaded ring components could be rationally controlled in these materials, providing a simple and versatile method to tune the mechanical and thermal properties. Specifically, a polyrotaxane with a high‐molecular‐weight axle became elastic upon heating above the melting point of PEOs and exhibited temperature‐dependent shape memory property because of the topological confinement and crosslinked hydrogen bonds. [ABSTRACT FROM AUTHOR]

The mobility, thermal behaviour, and crystal structures of water molecules confined within a one‐dimensional (1‐D), nanoporous single crystal in the premelting state were investigated in this study. Water clusters confined within the hydrophilic crystal revealed a premelting phase that was intermediate between the frozen and melted states. Water molecules in the premelting phase moved slowly. Heat capacity measurements showed that this motion could continue for approximately 24 hours after annealing at 160 K, although this could not be confirmed with solid‐state 2H‐NMR analysis. X‐ray diffraction analysis established the coexistence of crystal structures in the frozen and premelting states at 165 K. These results represent a valuable contribution to understanding the dynamic properties of water confined within nanoscale spaces. [ABSTRACT FROM AUTHOR]

Front Cover: Thermally Responsive Poly(ethylene oxide)-Based Polyrotaxanes Bearing Hydrogen-Bonding Pillar[5]arene Rings (Chem. Eur. J. 21/2021) Keywords: hydrogen bonds; pillar[n]arenes; poly(ethylene oxide); rotaxanes; supramolecular chemistry EN hydrogen bonds pillar[n]arenes poly(ethylene oxide) rotaxanes supramolecular chemistry 6354 6354 1 04/16/21 20210412 NES 210412 B Polyrotaxanes constructed b from hydrogen-bonding pillar[5]arene rings and poly(ethylene oxide) chains were synthesized. The hydrogen bond networks constructed from pillar[5]arene rings and poly(ethylene oxide) chains are illustrated as music notes and staff notation, respectively. [Extracted from the article]