Single-walled carbon nanotubes (SWCNTs)
synthesized by the improved
arc discharge method were modified with a fluorocarbon chain, and
the maintenance of trypsin activity upon adsorption from the subphase
to the interfacial monolayer of SWCNTs was evaluated. The adsorption
of trypsin on the fluorocarbon-modified SWCNT monolayer was confirmed
by morphological and spectroscopic evaluations. Fiber morphology studies
revealed that the fluorocarbon-modified SWCNT monolayer was covered
by trypsin, and a trypsin-derived amide band was detected in the infrared
spectra of the multilayers. After adsorption onto the fluorocarbon-modified
SWCNT film, the ability of trypsin to cleave the fluorescent casein
chain was maintained even at 160 °C. Furthermore, circular dichroism
(CD) spectra showed that the second-order structure of the activity
of trypsin adsorbed on the fluorocarbon-modified SWCNT was maintained
up to nearly 200 °C. At 200 °C, the enhancement of emission
intensity by casein chain cleavage was negligible, and the CD signal
resulting from the negative Cotton effect was completely altered at
250 °C.
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.
A technique for improving the dispersibility of fluorocarbon-modified, singlewalled carbon nanotubes (SWCNTs) in fluorinated polymers was investigated. Furthermore, we aimed to achieve uniaxial orientation of SWCNT aggregates via a simple high-temperature drawing method to yield fluoropolymer-based nanocomposites containing uniform dispersed SWCNTs. Highly waterrepellent SWCNTs were mixed with phase-separable fluorinated polymers by the chemical modification of their surfaces with fluorocarbons. Introducing a fluorinated phosphonic acid surfactant with a high-sublimation temperature as the third component to improve dispersibility in the polymer matrix resulted in an innovative improvement. The uniform dispersed SWCNTs in the matrix improved the crystallinity, crystallization temperature, and mechanical characteristics of the composites. The high-temperature uniaxial orientation of the composite material reduced differences in the physical properties in the polymer due to differences in the initial dispersibility. This effect was expected since the drawing process promoted the deagglomeration of SWCNTs in the matrix. However, optimal physical properties were observed in SWCNT-oriented composite samples with an excellent initial dispersion.
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.
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