Synthesis of High χ–Low N Diblock Copolymers by Polymerization‐Induced Self‐Assembly

Polymerization‐induced self‐assembly (PISA) enables the scalable synthesis of functional block copolymer nanoparticles with various morphologies. Herein we exploit this versatile technique to produce so‐called “high χ–low N” diblock copolymers that undergo nanoscale phase separation in the solid state to produce sub‐10 nm surface features. By varying the degree of polymerization of the stabilizer and core‐forming blocks, PISA provides rapid access to a wide range of diblock copolymers, and enables fundamental thermodynamic parameters to be determined. In addition, the pre‐organization of copolymer chains within sterically‐stabilized nanoparticles that occurs during PISA leads to enhanced phase separation relative to that achieved using solution‐cast molecularly‐dissolved copolymer chains.     

Mapping parameters across system boundaries: parameterized model reduction with low rank variability in dynamics

Linear dynamical systems with an affine parameter dependence producing low-rank variation in the state matrix can be recast as a nonparameterized system operating in parallel with a parameterized feed forward term operating under output constraints. This mapping permits the application of standard (nonparametric) model reduction strategies to solve parameterized problems. We demonstrate the approach on a parameterized vibration problem using optimal tangential interpolation. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Limits on neutrino emission from gamma-ray bursts with the 40 string IceCube detector

IceCube has become the first neutrino telescope with a sensitivity below the TeV neutrino flux predicted from gamma-ray bursts if gamma-ray bursts are responsible for the observed cosmic-ray flux above 10(18) eV. Two separate analyses using the half-complete IceCube detector, one a dedicated search for neutrinos from pγ interactions in the prompt phase of the gamma-ray burst fireball and the other a generic search for any neutrino emission from these sources over a wide range of energies and emission times, produced no evidence for neutrino emission, excluding prevailing models at 90% confidence.     

Proline-catalysed amination reactions in cyclic carbonate solvents

Propylene carbonate is shown to be an environmentally friendly and sustainable replacement for dichloromethane and acetonitrile in proline-catalysed a-hydrazinations of aldehydes and ketones. Enantioselectivities comparable to those obtained in conventional solvents or ionic liquids can be obtained, even when using a lower catalyst loading.     

A sequential cyclization/π-extension strategy for modular construction of nanographenes enabled by stannole cycloadditions

The synthesis of polycyclic aromatic hydrocarbons (PAHs) and related nanographenes requires the selective and efficient fusion of multiple aromatic rings. For this purpose, the Diels–Alder cycloaddition has proven especially useful; however, this approach currently faces significant limitations, including the lack of versatile strategies to access annulated dienes, the instability of the most commonly used dienes, and difficulties with aromatization of the [4 + 2] adduct. In this report we address these limitations via the marriage of two powerful cycloaddition strategies. First, a formal Cp₂Zr-mediated [2 + 2 + 1] cycloaddition is used to generate a stannole-annulated PAH. Secondly, the stannoles are employed as diene components in a [4 + 2] cycloaddition/aromatization cascade with an aryne, enabling π-extension to afford a larger PAH. This discovery of stannoles as highly reactive – yet stable for handling – diene equivalents, and the development of a modular strategy for their synthesis, should significantly extend the structural scope of PAHs accessible by a [4 + 2] cycloaddition approach.

Stannoles are introduced as a new, spontaneously aromatizing diene for [4 + 2] cycloadditions that can be easily introduced into diverse conjugated systems, facilitating the efficient synthesis of complex PAHs and their π-extension.