New acid/base salts as co‐catalysts for the organocatalyzed ring opening polymerization of lactide

(R)‐(+)‐binaphathyl‐diyl hydrogen phosphate (BNPH)/ diazabicyclo[5.4.0]undec‐7‐ene (DBU) and (1R)‐(?)?10‐camphorsulfonic acid (CSA)/4‐dimethylaminopyridine (DMAP) acid–base salts were synthesized and assessed for the ring‐opening polymerization of rac‐lactide. They were found to be inactive toward the polymerization in the presence of a protic initiator. When used in combination with a base such as DBU or DMAP and a protic initiator, these acid/base conjugates led to well‐controlled polymerization in mild conditions (D_M < 1.1 in all cases). With DBU, the presence of the salt was found to lead to narrower molecular weight distributions than those obtained using the base alone, and to prevent undesirable transesterification reactions occurring at the end of the reaction. An increase in activity was observed using the salts in combination with DMAP as compared with DMAP alone, together with an improvement of the control over the molecular weight. The results were discussed on the basis of ¹H nuclear magnetic resonance analyzes including acid/base equilibria involving the use of two different bases. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 659–664     

The complex dispersion relation of surface plasmon polaritons at gold/para-hexaphenylene interfaces

Two-photon photoemission electron microscopy (2P-PEEM) is used to measure the real and imaginary part of the dispersion relation of surface plasmon polaritons at different interface systems. A comparison of calculated and measured dispersion data for a gold/vacuum interface demonstrates the capability of the presented experimental approach. A systematic 2P-PEEM study on the dispersion relation of dielectric-loaded gold surfaces shows how effective the propagation of surface plasmon polaritons at a gold/para-hexaphenylene interface can be tuned by adjustment of the dielectric film thickness. Deviations of the experimental results from effective index calculations indicate the relevance of thin film peculiarities arising from the details of the growth process and corroborate the need of experimental analysis techniques for dispersion relation measurements.     

Imaging of trapped ions with a microfabricated optic for quantum information processing

Trapped ions are a leading system for realizing quantum information processing (QIP). Most of the technologies required for implementing large-scale trapped-ion QIP have been demonstrated, with one key exception: a massively parallel ion-photon interconnect. Arrays of microfabricated phase Fresnel lenses (PFL) are a promising interconnect solution that is readily integrated with ion trap arrays for large-scale QIP. Here we show the first imaging of trapped ions with a microfabricated in-vacuum PFL, demonstrating performance suitable for scalable QIP. A single ion fluorescence collection efficiency of 4.2±1.5% was observed. The depth of focus for the imaging system was 19.4±2.4 μm and the field of view was 140±20 μm. Our approach also provides an integrated solution for high-efficiency optical coupling in neutral atom and solid-state QIP architectures.     

Floating carpets and the delamination of elastic sheets

We investigate the deformation of a thin elastic sheet floating on a liquid surface and subject to a uniaxial compression. We show that at a critical compression the sheet delaminates from the liquid over a finite region forming a delamination "blister." This blistering regime adds to the wrinkling and localized folding regimes that have been studied previously. The transition from wrinkled to blistered states occurs when delamination becomes energetically favorable compared with wrinkling. We determine the initial blister size and the evolution of blister size with continuing compression before verifying our theoretical results with experiments at a macroscopic scale.     

A 2,6‐Bis(phenylamino)pyridinato Titanium Catalyst for the Highly Regioselective Hydroaminoalkylation of Styrenes and 1,3‐Butadienes

The C? C bond forming catalytic hydroaminoalkylation of terminal alkenes, 1,3‐dienes, or styrenes allows a direct and highly atom efficient (100 %) synthesis of amines which can result in the formation of two regioisomers, the linear and the branched product. We present a new titanium catalyst with 2,6‐bis(phenylamino)pyridinato ligands for intermolecular hydroaminoalkylation reactions of styrenes and 1‐phenyl‐1,3‐butadienes that delivers the corresponding linear hydroaminoalkylation products with excellent regioselectivities.     

Transient excited-state absorption of the liquid crystal CB15 [4-(2-methylbutyl)-4-cyanobiphenyl] in its isotropic phase

Liquid crystals are known to possess large electronic optical non-linearities. Transient photoinduced absorption is not commonly applied to liquid crystals, but it is a powerful technique by which to examine the excited-state absorption (ESA) and hence the non-linear absorption of molecular systems. We show that measurements of this kind can give an insight into the dominant mechanisms of picosecond non-linear optical response in liquid crystals, and together with semi-empirical quantum chemical calculations appropriate assignments of the absorptions can be made. In particular, we report measurements of the transient ESA of the liquid crystal CB15 [4-(2-methylbutyl)-4-cyanobiphenyl] in its isotropic phase using femtosecond pump-probe spectroscopy in the wavelength range from 400 to 1000 nm. By pumping directly into the first excited state (S₁) we identify at least four transient ESAs which contribute to the non-linear response up to a time of 1 ns after excitation. These features show a linear dependence with pump intensity. There also exists weak two-photon absorption (TPA) into S₁ at 650 nm, giving a similar ESA. Furthermore, we show that a semi-empirical quantum-chemical treatment of a single molecular unit of CB15 using the AMI Hamiltonian gives good agreement with the observed spectra, and implies that the dominant ESA in the picosecond regime can be attributed principally to singlet-singlet transitions from monomer units; but there is also a possible contribution to the ESAs by excimer absorption. On the time scale of our experiment we see no evidence of triplet-triplet absorptions, and we have also measured a fluorescence quantum yield of 20%.     

ESCA and optical emission study of the inductively coupled RF plasma copolymerization of naphthalene and octafluoronaphthalene mixtures

Plasma polymerization of octafluoronaphthalene, naphthalene, and 1 : 1 mixtures of the two yielded thin films which were then analyzed by ESCA. Optical emission was recorded during deposition and the resultant spectra are shown. Deposition of the copolymer at 150°C resulted in a film whose composition was different from that deposited at room temperature and from the single plasma polymers. Copolymerization resulted in a lowering of CF₂ functionalities and an increased retention of the aromatic nature of the monomers. Optical emission of CF₂ during copolymerization was greatly reduced as was a peak at about 510 nm.     

Purification and characterization of commercial NADH and accompanying dehydrogenase inhibitors.

The anion-exchange chromatography of commercial NADH using a potassium bicarbonate solution as eluent yields highly pure NADH with good stability. Twelve compounds are also separated which act as dehydrogenase inhibitors. The main impurities are further characterized. The compound mainly responsible for residual optical density in commercial NADH preparations is probably a stereoisomer of NADH which is in reversible equilibrium with NADH at pH values in the range 5-7. A method of thin-layer chromatography, to check commercial NADH preparations for impurities, is described.