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Abstract Gas-responsive polymers have recently attracted considerable interest as unconventional smart materials that provide a new path toward the utilization of specific gases including CO2. Herein, we report gas-responsive elastomers that enhance mechanical properties, such as modulus, strength, stretchability, and toughness with CO2 gas. Various types of amine groups are introduced into polydimethylsiloxane elastomers to achieve the gas-induced mechanical reinforcement. In these elastomers, the amines form ionic crosslinks with CO2 gas that mechanically strengthen the materials. Furthermore, nanodomains formed via microphase separation of the ionic components behave similarly to viscoelastic nanofillers that dissipate a large amount of energy during deformation, thereby remarkably toughening the elastomers. Surprisingly, the fracture energy of the elastomer with diamine increases ~35 times in CO2 gas compared with that in N2 gas. Furthermore, the elastomers sensitively respond even to CO2 gas concentrations as low as 10 % and are remarkably toughened. Our design concept is widely applicable to the CO2 reinforcement of other polymers, such as polyethylene.

Abstract Here, an unprecedented phenomenon in which 7‐coordinate lanthanide metallomesogens, which align via hydrogen bonds mediated by coordinated H2O molecules, form micellar cubic mesophases at room temperature, creating body‐centered cubic (BCC)‐type supramolecular spherical arrays, is reported. The results of experiments and molecular dynamics simulations reveal that spherical assemblies of three complexes surrounded by an amorphous alkyl domain spontaneously align in an energetically stable orientation to form the BCC structure. This phenomenon differs greatly from the conventional self‐assembling behavior of 6‐coordinated metallomesogens, which form columnar assemblies due to strong intermolecular interactions. Since the magnetic and luminescent properties of different lanthanides vary, adding arbitrary functions to spherical arrays is possible by selecting suitable lanthanides to be used. The method developed in this study using 7‐coordinate lanthanide metallomesogens as building blocks is expected to lead to the rational development of micellar cubic mesophases.

Abstract Dynamic crosslinking of flexible polymer chains via attractive and reversible interactions is widely employed to obtain autonomously self-healable elastomers. However, this design leads to a trade-off relationship between the strength and self-healing speed of the material, i.e., strong crosslinks provide a mechanically strong elastomer with slow self-healing property. To address this issue, we report an “inversion” concept, in which attractive poly(ethyl acrylate-random-methyl acrylate) chains are dynamically crosslinked via repulsively segregated fluoroalkyl side chains attached along the main chain. The resulting elastomer self-heals rapidly (> 90% within 15 min) via weak but abundant van der Waals interactions among matrix polymers, while the dynamic crosslinking provides high fracture stress (≈2 MPa) and good toughness (≈17 MJ m−3). The elastomer has a nonsticky surface and selectively self-heals only at the damaged faces due to the surface segregation of the fluoroalkyl chains. Moreover, our elastomer strongly adheres to polytetrafluoroethylene plates (≈60 N cm−2) via hot pressing.

Usually self-healing materials require heat or light as a stimulus which can limit their application. Here the authors show an elastomer with an ionically crosslinked silicone network that quickly self-heals damage in the presence of CO2 gas at standard pressures and room temperature.

Smectic C (SmC) to cubic (Cub) phase transition behavior of 4′-n-docosyloxy-3′-nitrobiphenyl-4-carboxylic acid (ANBC-22) and alternating-current (AC) electric field effect on the SmC phase were examined. The most important and unexpected finding is that even at a temperature 8 K below the zero-field SmC to Cub phase transition temperature (TSmC−Cub≈ 408 K) determined previously for the compound and without field, the Cub phase growth occurs, after a very long induction period of several hours. The X-ray diffraction measurements revealed the formation of an Im3m-type Cub phase at the temperature. It is suggested that the “true” transition temperature, which is difficult to determine precisely, exists around 396 K. The time-dependence of the Cub phase growth both without field and under field was analyzed using the well-known Avrami equation, implying the nucleation and growth mechanism mainly operating in the SmC to Cub phase transformation. The fact uncovered is that between 408 and 396 K, the SmC to Cub transformation is virtually prohibited by the strongly limited nucleation. It is concluded that the effect of the electric field on the transition is to promote the nucleation of the Cub phase in the temperature region where the Cub phase is potentially more stable than the precursory SmC phase. [ABSTRACT FROM AUTHOR]

The phase transitions of a homologous series of 1,2-bis(4′- n-alkoxybenzoyl)hydrazines (BABH- n, where nis the number of carbon atoms in the alkyl chain and in this investigation varies from 4 to 22) were investigated by differential scanning calorimetric (DSC), polarizing optical microscopic (POM), X-ray diffraction (XRD), and infrared (FT-IR) measurements. The formation of bicontinuous type cubic (Cub) mesophases was observed enantiotropically for n≥ 6 and only on cooling for n= 5. The structures were examined by XRD, which revealed the presence of two types with symmetries Ia3 dand Im3 m, depending on n, and for n= 13, 15, and 16, phase transitions between the two Cub phases were observed. The FT-IR studies elucidated the formation of intermolecular hydrogen bonding between the CO bond of one molecule and the NH group of another molecule, whose binding strength was temperature-dependent. The temperature dependence of the Cub lattice parameter (d a/d T) varied from a large positive to a large negative value with increasing alkyl chain length n, which can be well-explained in terms of the temperature-responsive shape change of the constituent molecules. The packing structures of two Ia3 d-Cub phases formed by shorter and longer alkyl chain members are compared and discussed. It is revealed that two competitive mechanisms are mainly operated on the self-organization, i.e., the preferential orientation of the long axes of the aromatic core parts parallel to each other and microsegregation between the aromatic core and alkyl chain parts of the molecules; the former mechanism is effective in the shorter chain members, whereas the latter is predominant in the longer chain members. [ABSTRACT FROM AUTHOR]

Phase transition behavior of 1,2-bis(4'-n-hexyloxybenzoyl)hydrazine (BABH(6)) was studied by differential scanning calorimetry (DSC) and polarizing microscopy. While the DSC trace above melting temperature is consistent with the existing report, it is not for crystalline states. A number of tiny and spiky anomalies was observed in the first cooling run whereas the number of anomalies decreases, and finally disappeared in repeated runs. Microscopic observation revealed that the tiny and spiky anomalies arise from collapsing of crystals. When the sample was cooled from the cubic phase (430 K), the tiny and spiky anomalies revived on the cooling process, which can be ascribed to the liquid-crystallinity of the cubic phase. [ABSTRACT FROM AUTHOR]