Conformational Sensitivity in Photoelectron Circular Dichroism of 3‐Methylcyclopentanone

A study of (R)‐3‐methylcyclopentanone [(R)‐3‐MCP] by photoelectron spectroscopy and photoelectron circular dichroism (PECD) is presented. The synchrotron radiation gas‐phase photoelectron spectra of (R)‐3‐MCP were measured and are discussed on the basis of different theoretical methodologies. The experimental dichroism of (R)‐3‐MCP for selected deconvoluted valence states and for the carbonyl carbon 1s core state are reported and reproduced well by calculated dispersions generated by considering the contributions of two different conformers. The theoretical dichroic parameters are calculated by employing a multicentre basis set of B‐spline functions and a Kohn–Sham Hamiltonian. Temperature‐dependent PECD studies of the HOMO state and the carbonyl carbon 1s core level allowed the separation of the contributions of each conformer by photoelectron dichroism. This new approach clearly shows how the PECD methodology is sensitive to conformational and structural changes of unoriented (R)‐3‐MCP in the gas phase, opening up new perspectives in the characterisation of chiral molecular systems.     

“Green polyethylene” and curauá cellulose nanocrystal based nanocomposites: Effect of vegetable oils as coupling agent and processing technique

Cellulose nanocrystals (CNC) were prepared from curauá fibers via acid hydrolysis, and used as reinforcing phase for high‐density biopolyethylene (HDBPE) or green polyethylene. Castor oil (CO), epoxidized soybean oil (ESO) and epoxidized linseed oil (ELO) were chosen as compatibilizers for this study. Nanocomposites reinforced with CNC (3, 6, and 9 wt %) were processed by extrusion, using CO (3, 6, and 9 wt %) to evaluate its action as CNC dispersing agent in the HDBPE matrix. From the results obtained for these films, the CNC and oil contents were set at 3 wt%. In addition to CO, ELO, and ESO were also used, and besides processing by extrusion, extrusion/hot‐pressing process was also considered, in order to compare the two processing techniques. The nanocomposites were characterized by microscopic, thermal, mechanical, and rheological analyses. The presence of oil leads to less opaque films and improved dispersion. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1010–1019     

Rapid Access to 1-Benzyl 2-Substituted Piperazines: Application to the Synthesis of 1-Benzyl-2-difluoromethyl-Piperazine

A rapid and efficient synthesis of 1-benzyl-2-difluoromethyl-piperazine is herein described. The new pathway has the advantage of avoiding orthogonal protection at the two piperazine nitrogen atoms; therefore it is suitable for access to several 1-benzyl 2-substituted piperazines starting from the simple commercially available N,N′-dibenzylethylendiamine.     

Viscoelasticity of nanobubble‐inflated ultrathin polymer films: Justification by the coupling model

The nanobubble inflation method is the only experimental technique that can measure the viscoelastic creep compliance of unsupported ultrathin films of polymers over the glass–rubber transition zone as well as the dependence of the glass transition temperature (T_g) on film thickness. Sizeable reduction of T_g was observed in polystyrene (PS) and bisphenol A polycarbonate by the shift of the creep compliance to shorter times. The dependence of T_g on film thickness is consistent with the published data of free‐standing PS ultrathin films. However, accompanying the shift of the compliance to shorter times, a decrease in the rubbery plateau compliance is observed. The decrease becomes more dramatic in thinner films and at lower temperatures. This anomalous viscoelastic behavior was also observed in poly(vinyl acetate) and poly (n‐butyl methacrylate), but with large variation in the change of either the T_g or the plateau compliance. By now, well established in bulk polymers is the presence of three different viscoelastic mechanisms in the glass–rubber transition zone, namely, the Rouse modes, the sub‐Rouse modes, and the segmental α‐relaxation. Based on the thermorheological complexity of the three mechanisms, the viscoelastic anomaly observed in ultrathin polymer films and its dependence on chemical structure are explained in the framework of the Coupling Model. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Synthesis and Characterization of HgII/Se/CuI Multinuclear Compounds from Mercury(II) Bis(p‐aminobenzeneselenolate) – Hg(SeC6H4NH2‐p)2

In this paper we explore an amino functionalized selenolate unit for the synthesis of new multinuclear compounds with promising interesting properties and potential precursors of semiconductors. We present for the first time the X‐ray crystallographic structure of [Hg(SeC₆H₄NH₂)₂]₂ · diox ( 1· diox) and its copper(I) derivatives: HgCu₂X₂(SeC₆H₄NH₂)₂(PPh₃)₄ · 4diox [X = Br ( 2· 4diox) and I ( 3· 4diox)]. The compounds 1 and 2 , 3 can be considered as the starting material and intermediates, respectively, for the synthesis of ternary Hg^II/Se/Cu^I nanoclusters. We also provide IR and NMR spectroscopic data and evaluate the optical features of these compounds by difuse reflectance UV/Vis spectroscopy.     

The multi-stage dynamic stochastic decision process with unknown distribution of the random utilities

We consider a decision maker who performs a stochastic decision process over a multiple number of stages, where the choice alternatives are characterized b