No abstract

No abstract

The dispersion of hydrophilized single-walled carbon nanotube (SWCNT) in organic solvent, through the modification of its surface by bidentate long-chain phosphonic acid with excellent heat resistance, and its structural characterization, through the formation of a monolayer on the water surface, have been performed. The surface-modified chains were developed by both hydrocarbon-based and fluorocarbon-based modifiers, and the arrangement of the organized films of each modified SWCNT was evaluated. The modified nanotubes were uniformly dispersed in toluene solvent, facilitating the confirmation of its lipophilicity, and spread as a monolayer at the air-water interface. The morphology of the organo-SWCNT monolayer was fibrous. In the Raman spectrum of the modified-SWCNT Langmuir-Blodgett multilayers, the defect-derived D band shifted to lower wavenumbers. The above experimental results confirmed the non-desorptive property of the modifiedbidentate chain. The packing and orientation of the modified chains were evaluated through out-of-plane and in-plane X-ray diffraction and polarized infrared spectroscopy. In addition, the monolayer of organo-SWCNT was densified with a small number of defects by the "repeating compression-expansion method". Furthermore, activation of the lysozyme enzyme from the subphase caused adsorption and immobilization onto organo-SWCNT monolayers. The introduction of SWCNTs to the air-water interface has revealed the potential for nanostructural control and the estimation of interactions between biomolecules.

The orientation effect of sepiolite natural clay, a needle‐shaped nanoparticle, in a polymer matrix was investigated. Uniaxial drawing was performed on polymer‐based nanocomposites containing organo‐modified sepiolite, achieving uniform dispersion in the crystalline polymer by modifying the surface with organic molecular chains. Fluorinated polymer was used as the matrix, and sepiolite was modified using fluorinated chains. High‐temperature drawing was conducted to increase the density of amorphous chains in the fluoropolymer. Observations confirmed the orientation of the nanofiller in the drawing direction. When the filler content was intentionally increased, it was as if it were a nanosized mille‐feuille. As a result of 5× drawing, a 20% improvement in crystallinity was calculated. Small‐angle X‐ray scattering (SAXS) analysis showed a 32 Å increase in long‐period values. When high‐drawing was conducted, some amorphous parts transformed into crystals, and the difference in electron densities between the two regions widened, increasing the long‐period value while decreasing the SAXS intensity. The crystallization temperature increased by 1.8°C, and the Young's modulus calculated from the strain‐stress curve showed a nearly 4× increase. The mechanical strength doubled when the neat fluoropolymer was drawn five times. This provides a clear understanding of the enhancement behavior of the structural and physical properties of a uniform dispersible polymer/needle nanoparticle nanocomposite using uniaxially oriented nanofillers.

Polymer‐based nanohybrid materials were created using sustainable sepiolite clay composed from ubiquitous elements. Although sepiolite is generally recognized as a fibrous natural clay mineral, it turned out to be an acicular microcrystal because of the organo‐modification of the outermost surface. Surface modification was performed using phosphonic acid derivatives containing hydrocarbon chains or fluorocarbon chains. Formation of a bidentate bond enhanced the desorption temperature and made nanocomposite preparation possible by melt compounding with polymers having a high melting point. As a result of organo‐modification, amphiphilic sepiolite was obtained, and nanodispersion in an organic solvent was achieved. This technology was useful for detailed evaluation of sepiolite morphology. The nanocomposite of crystalline polymers/organo‐modified sepiolites achieved uniform dispersion of these nanofillers in the matrix polymer. The introduction of 1 wt% nanofillers did not impair the transparency of the matrix polymer. As a result, a lamellae structure of the polymer developed, the crystallinity increased, and the mechanical properties improved. In addition, the crystallization temperature was improved, indicating that organo‐modified sepiolites may act as a nucleating agent. It was found that sepiolite nanofiller with a highly aggregated tendency can achieve a well‐nanodispersed state, even in phase‐separable fluoropolymers, by applying fluorocarbon modification. POLYM. ENG. SCI., 60:541–552, 2020. © 2019 Society of Plastics Engineers