Understanding the Mechanocatalytic Conversion of Biomass: A Low‐Energy One‐Step Reaction Mechanism by Applying Mechanical Force

On the way to establishing biomass as a renewable and environmentally friendly source to cover the ever‐increasing global demand on energy and chemicals, one great challenge is the efficient depolymerization of cellulose. Enhanced conversion rates have been discovered in ball‐milling experiments, thus opening a mechanocatalytic approach. However, an understanding of the impact of mechanical forces on the acid‐catalyzed cleavage of glycosidic bonds at the molecular level is still missing. Herein, we contribute such fundamental insight based on atomistic modeling. Mechanically stressing the macromolecular backbone radically changes the depolymerization pathway from a complex high‐barrier reaction upon thermal activation to a low‐energy single‐step mechanocatalytic process. In addition to revealing a regioselective increase in basicity under a mechanical force, our results provide molecular‐level explanations of the experimental findings and might therefore guide rational ways to improve such mechanocatalytic processes.     

Numerical simulation of the effect of grain fragmentation on the evolution of microstructure quantities

Meccanica - In this paper the effect of grain fragmentation of a cohesionless granular material on the change of microstructure quantities is investigated using a micropolar continuum model. To...     

Multicomponent reaction of amine,carbon disulfide,and fluoronitrobenzene via nucleophilic attack on the fluorinated carbon for the synthesis of nitrophenyl methylcarbamodithioates

In this paper, multicomponent reaction of amine, carbon disulfide and fluoronitrobenzene is reported for the synthesis of nitrophenyl methylcarbamodithioate derivatives. The method is based on the nucleophilic attack of the activated methylcarbamodithioate salt to fluoronitrobenzene. Several starting materials are tested and successfully produced the corresponding nitrophenyl methylcarbamodithioate. A possible mechanism for the reaction is suggested.     

Synthesis and self‐assembly of thermosensitive double‐hydrophilic poly(N‐vinylcaprolactam)‐b‐poly(N‐vinyl‐2‐pyrrolidone) diblock copolymers

We report on novel diblock copolymers of poly(N‐vinylcaprolactam) (PVCL) and poly(N‐vinyl‐2‐pyrrolidone) (PVPON) (PVCL‐b‐PVPON) with well‐defined block lengths synthesized by the MADIX/reversible addition‐fragmentation chain transfer (RAFT) process. We show that the lower critical solution temperatures (LCST) of the block copolymers are controllable over the length of PVCL and PVPON segments. All of the diblock copolymers dissolve molecularly in aqueous solutions when the temperature is below the LCST and form spherical micellar or vesicular morphologies when temperature is raised above the LCST. The size of the self‐assembled structures is controlled by the molar ratio of PVCL and PVPON segments. The synthesized homopolymers and diblock copolymers are demonstrated to be nontoxic at 0.1–1 mg mL^?1 concentrations when incubated with HeLa and HEK293 cancer cells for various incubation times and have potential as nanovehicles for drug delivery. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2725–2737     

A comparative study on the catalytic performance of heme and non‐heme catalysts: Metal porphyrins versus metal Schiff bases

Catalytic activity and oxidative stability of a series of iron and manganese porphyrins with 2‐chlorophenyl, phenyl and 4‐methoxyphenyl at the meso positions and metallosalens (Mn‐ and Fe‐salens) including N,N′‐bis(salicylidene)ethylenediamine, N,N′‐bis(5‐ chlorosalicylidene)ethylenediamine and N,N′‐bis(2,4‐dihydroxysalicylidene)ethylenediamine for the oxidation of olefins with tetra‐n‐butylammonium periodate (TBAP) and tetra‐n‐butyl‐ammonium Oxone (TBAO) have been investigated and compared. Although the metalloporphyrins showed an increased catalytic activity relative to the Schiff base complexes, the former provided no significant catalytic advantage over the latter. Also, a comparable or slightly higher oxidative stability was observed for the Schiff base complexes under the reaction conditions. Furthermore, in spite of large difference between the oxidizing ability of TBAO and TBAP, similar patterns were observed for the order of catalytic activity and oxidative stability of the used heme and non‐heme catalysts. The introduction of a methyl group at the ɑ position of styrene led to an increase in its reactivity, indicating the dominance of electronic effects over the steric ones in these catalytic systems.     

Ion-solvent and ion-ion interactions of NaCl aqueous and aqueous maltose solutions at 298–323 K on viscosity data

Viscosities of sodium chloride in concentration range 1 × 10^?2 to 9 × 10^?2 ± 0.001 mol dm^?3, have been determined in aqueous and aqueous maltose systems (1.0 to 9.0 wt %) at different temperatures (298 to 323 K). The viscosity data have been analyzed by using Jones-Dole equation and the derived parameters A and B coefficients were also calculated. The data obtained from viscometric studies has been used to investigate the ion-solvent interaction and ion-ion interaction. Thermal effects on the ionic interactions were also examined under the light of transition state theory.     

Optical diffusers based on uniform nano-sized polymer balls/nematic liquid crystals composite films

ABSTRACT

Optical diffusers are promising diffusing materials in the optical devices such as monitors, projectors, fibre optics, light-emitting diode (LED) systems and liquid crystal displays (LCDs). We report optical diffusers comprising uniformly distributed nano-sized polymer balls/nematic liquid crystals (LCs) by ultraviolet (UV) click reaction of ene monomer and thiol monomer. By optimising the mass ratio 1:1 of ene and thiol, of which the average diameter of the corresponding nano-sized polymer balls is about 900 nm, relatively high optical transmission and haze with 88.99% and 94.49% are yielded, respectively. Furthermore, by controlling the curing time, the average diameter of nano-sized polymer balls can be reduced to 810 nm, and the developed film exhibits high transmission (98.49%) without sacrificing the high haze (91.77%). This paper demonstrates that UV click reaction is an economical approach to fabricate optical diffusers in a controllable manner.