: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Inspired by rich physics and functionalities of graphenes, scientists have taken an intensive interest in two-dimensional (2D) crystals of h-BN (analogue of graphite, so-called "white" graphite). Recent calculations have predicted the exciting potentials of BN nanoribbons in spintronics due to tunable magnetic and electrical properties; however no experimental evidence has been provided since fabrication of such ribbons remains a challenge. Here, we show that few- and single-layered BN nanoribbons, mostly terminated with zigzag edges, can be produced under unwrapping multiwalled BN nanotubes through plasma etching. The interesting stepwise unwrapping and intermediate states were observed and analyzed. Opposed to insulating primal tubes, the nanoribbons become semiconducting due to doping-like conducting edge states and vacancy defects, as revealed by structural analyses and ab initio simulations. This study paves the way for BN nanoribbon production and usage as functional semiconductors with a wide range of applications in optoelectronics and spintronics.

"White graphenes": boron nitride nanoribbons via boron nitride nanotube unwrapping

Factors affecting thermal conductivities of the polymers and polymer composites: A review

Phosphorus-containing flame retardant epoxy thermosets: Recent advances and future perspectives

Covalent organic frameworks offer a molecular platform for integrating organic units into periodically ordered yet extended two- and three-dimensional polymers to create topologically well-defined polygonal lattices and built-in discrete micropores and/or mesopores. This polymer architecture is unique as it enables predesigning both primary- and high-order structures, greatly enhancing our capabilities of designing organic materials to produce predictable structures and to achieve unique properties and functions. Progress over the past 15 years in the design, synthesis and functional exploration of COFs has successively established the basis of the COF field and COFs have shown the great potential of chemistry in developing a class of amazing organic materials. In this review, we focus on analysing the historic developments of COFs to uncover a full materials and application picture by providing comprehensive yet clear guidance for molecular design, synthetic control and functional exploration. We scrutinise the structural components of COFs including building blocks, reactive sites and functional groups with the aim of finding the origins of structural designability and diversity, as well as multiple functionalities. We disclose strategies for designing and synthesising frameworks to construct various tailor-made interfaces, and for exploring skeletons and pores to design properties and functions. With well-defined skeletons, pores and interfaces that offer a chemical basis to trigger and control interactions with photons, excitons, phonons, polarons, electrons, holes, spins, ions and molecules, we illustrate the current status of our understandings of structure-property correlations, and unveil the principles for establishing a regime to design unique functions that originate from and are inherent to structures. We predict the key central issues in design and synthesis, the challenges in functional design and the future directions from the perspectives of chemistry, physics and materials science.

Covalent organic frameworks: an ideal platform for designing ordered materials and advanced applications

Enhancing interfacial properties of carbon fibers reinforced epoxy composites via Layer-by-Layer self assembly GO/SiO2 multilayers films on carbon fibers surface

A DOPO-based phosphorus-nitrogen flame retardant bio-based epoxy resin from diphenolic acid: Synthesis, flame-retardant behavior and mechanism

The deposition of graphene oxide (GO) onto carbon fibers (CF) surface to form a hierarchical reinforcement structure has been achieved via various bonding types: van der Waals forces, zwitterionic interactions and covalent bonds. The functional groups, surface elements, contents of introduced GO, surface structures, morphologies and wettability of GO-deposited CF were characterized by FT-IR, XPS, TGA, Raman, SEM and Dynamic contact angle meter, respectively. Covalently grafting GO onto CF (CF-c-GO) has been proved to be the most effective way to improve the interfacial properties. Compared with pristine CF, the flexural strength, interlaminar shear strength and interfacial shear strength of CF-c-GO composites were increased by 28.7%, 22.7% and 50.6%, respectively. The CF-GO hierarchical composites featured a stronger interfacial bonding as evidenced by the fracture surface analysis, which demonstrated the enhancement in interfacial properties of hierarchical thermoplastic composites.

Improving interfacial properties of hierarchical reinforcement carbon fibers modified by graphene oxide with different bonding types

Second-order nonlinear optical (NLO) materials have been investigated for decades driven by the application requirements of electro-optic modulators for optical communication, optical switches, sensors, terahertz generation and detection. The prominent advantages of organic NLO materials are ultra-fast response and structural versatility, which gives the materials large NLO activity, good processability and other necessary properties for specific applications via suitable molecular engineering. In this review, historic and recent studies of organic dipolar chromophores in acentric alignment affording macroscopic anisotropy are overviewed. In particular, recent marked progress in the development of acentric bulky materials, including isolating chromophores to prevent centrosymmetric alignment, is focused on. We also review fascinating methods for the ordered alignment of chromophores, which include supramolecular interaction, light fields, electric fields and so on. It is hoped that better chromophore molecular structures and film construction techniques can be devised using suitable NLO films to achieve higher performances in optoelectronic devices.

Molecular engineering of organic chromophores and polymers for enhanced bulk second-order optical nonlinearity

Poly(ether ether ketone)/graphene/carbon fiber (PEEK/GE/CF) laminates with different weight percentages of GE were manufactured successfully through ball milling and hot-press processing. The effect of the GE on the morphology, thermal conductivity, friction performance, thermal and mechanical properties of composites was investigated. Scanning electron microscopy showed that the GE was uniformly distributed in matrix-rich regions. Thermal conductivity measurements demonstrated that addition of 0.7 wt% GE sharply improved the thermal conductivity of the laminates. Tribological tests revealed that the friction coefficient and wear rate rapidly decreased with the addition of GE. In the studied range, the friction reduction and wear resistance performance of PEEK/CF composites filled with 0.7 wt% GE is the most effective. Meanwhile, the obtained PEEK/GE/CF laminates also possessed excellent mechanical and thermal properties. Thus, graphene-reinforced PEEK/CF composites possessed better overall properties than conventional PEEK/CF composites.

Ming Li

Papers

Enhancing interfacial properties of carbon fibers reinforced epoxy composites via Layer-by-Layer self assembly GO/SiO2 multilayers films on carbon fibers surface

A DOPO-based phosphorus-nitrogen flame retardant bio-based epoxy resin from diphenolic acid: Synthesis, flame-retardant behavior and mechanism

Improving interfacial properties of hierarchical reinforcement carbon fibers modified by graphene oxide with different bonding types

Molecular engineering of organic chromophores and polymers for enhanced bulk second-order optical nonlinearity

Improvement of the thermal conductivity and friction performance of poly(ether ether ketone)/carbon fiber laminates by addition of graphene