The highly constrained b-amino acid ABOC induces different types of helices in b urea and 1:1 a/b amide oligomers. The latter can adopt 11/9- and 18/16-helical folds depending on the chain length in solution. Short peptides alternating proteinogenic a-amino acids and ABOC in a 2:1 a/b repeat pattern adopted an unprecedented and stable 12/14/14-helix. The structure was established through extensive NMR, molecular dynamics, and IR studies. While the 1:1 a-AA/ABOC helices diverged from the canonical a-helix, the helix formed by the 9-mer 2:1 a/b-peptide allowed the projection of the a-aminoacid side chains in a spatial arrangement according to the a-helix. Such a finding constitutes an important step toward the conception of functional tools that use the ABOC residue as a potent helix inducer for biological applications.

Opto-electronic properties of single-walled carbon nanotubes can be significantly modified by chromophore confinement into their hollow core. For instance, charge transfers are evidenced from Raman data analysis. First, by exciting nanotubes far from the optical absorption of the molecule, the Raman G-band signal exhibits a weak but significant up or downshift depending on the nanotube diameters. This behavior is consistent with a permanent electron transfer to the nanotube in the framework of the renormalization process 1. In addition, close to the molecule resonance, the magnitude of the G-band shift is enhanced for small diameter tubes, evidencing a photo-induced electron transfer. Finally, the Breit-Wigner-Fano lineshape (characteristic of electron-phonon coupling) of the Raman G-band can be strongly reduced for defective metallic nanotubes. After molecule functionalization, this peculiar profile is recovered, suggesting a back donation of electrons to the nanotube. Photoluminescence properties of semiconducting nanotubes are also significantly modified by chromophore confinement. The nanotube emission intensity is amplified after encapsulation. This exaltation depends on the nanotube diameter, and can be related to diameters exactly fitting the molecule size. The origin of the photoluminescence enhancement will be discussed.

We examine the excitonic nature of the E33 optical transition of the individual free-standing index-identified(23,7) single-walled carbon nanotube by means of the measurements of its radial-breathing-mode and G-modeRaman excitation profiles. We confirm that it is impossible to determine unambiguously the nature of its E33optical transition (excitonic vs band to band) based only on the excitation profiles. Nevertheless, by combiningRaman scattering, Rayleigh scattering, and optical absorption measurements on strictly the same individual(23,7) single-walled carbon nanotube, we show that the absorption, Rayleigh spectra, and Raman excitationprofiles of the longitudinal and transverse G modes are best fitted by considering the nature of the E33 transitionas excitonic. The fit of the three sets of data gives close values of the transition energy E33 and damping parameter. This comparison shows that the fit of the Raman excitation profiles provides with good accuracy the energy and damping parameter of the excitonic optical transitions in single-walled carbon nanotubes.

Binary c–T phase diagrams of organogelators in solvent are frequently simplified to two domains, gel and sol, even when the melting temperatures display two distinct regimes, an increase with T and a plateau. Herein, the c–T phase diagram of an organogelator in solvent is elucidated by rheology, DSC, optical microscopy, and transmitted light intensity measurements. We evidence a miscibility gap between the organogelator and the solvent above a threshold concentration, cL. In this domain the melting or the formation of the gel becomes a monotectic transformation, which explains why the corresponding temperatures are nonvariant above cL. As shown by further studies by variable temperature FTIR and NMR, different types of H-bonds drive both the liquid–liquid phase separation and the gelation.

Thermo-mechanically durable industrial polymer nanocomposites have great demand as structural components. In this work, highly competent filler design is processed via nano-modified of micronic SiO2/Al2O3 particulate ceramics and studied its influence on the rheology, glass transition temperature, composite microstructure, thermal conductivity, mechanical strength, micro hardness, and tribology properties. Composites were fabricated with different proportions of nano-modified micro-composite fillers in epoxy matrix at as much possible filler loadings. Results revealed that nano-modified SiO2/Al2O3 micro-composite fillers enhanced inter-particle network and offer benefits like homogeneous microstructures and increased thermal conductivity. Epoxy composites attained thermal conductivity of 0.8 W/mK at 46% filler loading. Mechanical strength and bulk hardness were reached to higher values on the incorporation of nano-modified fillers. Tribology study revealed an increased specific wear rate and decreased friction coefficient in such fillers. The study is significant in a way that the design of nano-modified mixed-matrix micro-composite fillers are effective where a high loading is much easier, which is critical for achieving desired thermal and mechanical properties for any engineering applications. Copyright © 2016 John Wiley & Sons, Ltd.

Wet acid oxidation treatment methods have been widely reported as an effective method to purify and oxidize the surface of industrial multi-walled carbon nanotubes (MWCNT). This work examines the use of a concentrated HNO3/H2SO4 mixture in an attempt to optimize the purification procedure of industrial MWCNT with diameter distribution statistics. It is shown that acid treatments of several hours are enough to purify the nanotubes. The electrical and thermal conductivities of epoxy composites containing 0.05-0.25 wt. % of acid-treated MWCNT has been studied. The electrical conductivity of the composites decreases by more than three orders, whereas the thermal conductivity of the same specimen increases very modestly as a function of the filler content.