Episodic synchronization via dynamic injection

We report the occurrence of spontaneous synchronizing events between two semiconductor lasers, when the emission of a frequency- and intensity-chaotic driving laser is unidirectionally coupled into a second stable response laser. The driving laser is driven chaotic by delayed optical feedback, the response laser is a device-identical solitary laser. We demonstrate the onset of an episodic synchronization regime when the two lasers are spectrally detuned with respect to each other. By a joint experimental and modeling analysis we can attribute the onset and the duration of the episodes to properties of spectral overlap of both lasers. This effect can even give rise to seemingly anticorrelated intensity behavior. We expect episodic synchronization to be a generic scenario for the loss of synchronization of chaotic oscillators exhibiting frequency cycles.     

Biphasic hydrosilylation in ionic liquids: a process set for industrial implementation

The biphasic hydrosilylation of 1-hexadecene with siloxane B9800 in a range of ionic liquids is reported. Of the ionic liquids tested, [C(4)py][BF(4)] and [C(4)-3-pic][BF(4)] offer the optimum compromise between activity and catalyst retention. Several platinum precatalysts were screened, of which K(2)PtCl(4) and Pt(PPh(3))(4) were found to give the best performance; the former provides the highest activity, while the latter offers higher stability and recyclability, and depending on the conditions, both can afford either homogeneous or soluble nanoparticle catalysts as the active species. A number of reaction parameters were varied, and the effects of oxygen, water, and chloride impurities on the reaction were studied. In addition, since nanoparticle catalysts were observed, various strategies to stabilize nanoparticles were screened, but none of them resulted in a superior catalytic system.     

Kinetic acidity of supramolecular imidazolium salts-effects of substituent, preorientation, and counterions on H/D exchange rates

The deprotonation of imidazolium salts to N-heterocyclic carbenes is often a decisive step in modern catalytic reactions. Therefore, we studied the H/D exchange of the C2 H of 15 imidazolium-substituted calix[4]arenes and 11 nonmacrocyclic model compounds in methanol/water (97:3). The influence of the counterion, substitution directly on the imidazolium unit or on the preorientating calixarene backbone could be studied. The observed exchange rates might give a rational for the suitability of the imidazolium salts as precursors in the Suzuki coupling.     

Trends in industrial polymer research

In the past decades a shift in paradigm took place in industrial polymer research for structural materials. Only a few new polymers based on new monomeric building blocks were developed. The main focus is now on tailoring improved “old polymers” with well-defined structure and properties based on a set of low cost “old” monomers using controlled polymerization mechanisms.