Visible-light-mediated selective arylation of cysteine in batch and flow

A mild visible-light-mediated strategy for cysteine arylation is presented. The method relies on the use of eosin Y as a metal-free photocatalyst and aryldiazonium salts as arylating agents. The reaction can be significantly accelerated in a microflow reactor, whilst allowing the insitu formation of the required diazonium salts. The batch and flow protocol described herein can be applied to obtain a broad series of arylated cysteine derivatives and arylated cysteine-containing dipeptides. Moreover, the method was applied to the chemoselective arylation of a model peptide in biocompatible reaction conditions (room temperature, phosphate-buffered saline (PBS) buffer) within a short reaction time

Controlling Molecular Weight Distributions Through the Mixing of Low Dispersity Polymer Samples: A Predictive Framework

The physical properties of polymer samples are dependent on the overall shape and breadth of the molecular weight distribution (MWD). A small number of methods are available to tune the shape and characteristics of MWDs based on influencing controlled radical polymerizations and on mixing of individual distributions. However, no systematic framework exists to date to predict the characteristics and shapes of artificial MWDs prior the experiments. In this work we present such framework based on interpolation of individual distributions.</div

Photo-induced ring-closure via a looped flow reactor

Looped flow processes are an efficient and versatile tool to synthesize complex macromolecular materials. Especially for light-induced ring-closure reactions, which typically require low concentrations, looped flow processes are critical for upscaling. Here, such a reactor was designed to carry out a photo-induced ring-closure reaction via a photo-enol reaction for the synthesis of cyclic polymers, leading to a reduction of required solvent in the synthesis by over a factor of 40, hence giving access to a more economical and fully scalable process

The effects of molecular weight dispersity on block copolymer self-assembly

The influence of dispersity in the molecular weight distributions in the core forming block for block copolymer (BCP) self-assembly is analyzed via an automated flow synthesis approach. Polystyrenes with increasing dispersity in the core forming block are synthesized from reversible addition–fragmentation chain transfer (RAFT) polymerization with an average degree of polymerization (DPn) of 15 and 50 and dispersities between 1.10 and 1.45. After chain extension of these polymers with hydroxy ethyl acrylate, the residual BCPs were subjected to nanoaggregate formation via continuous flow mixing. Nanoaggregates were carefully analyzed with an ensemble of dynamic light scattering (DLS), scanning transmission electron microscopy (STEM) and small angle neutron scattering (SANS). With an increase in the dispersity of the core forming polymer block, the overall dispersity of the nanoparticles was reduced, demonstrating that lower polymer dispersities are not necessarily more advantageous to form uniform nanostructures. This unravels the fundamental role of molecular weight distribution shape in polymer self-assembly and introduces a new tool for tuning particle properties, specifically via continuous flow processes

Exploring the photochemical reactivity of multifunctional photocaged dienes in continuous flow

Flow reactors become more and more automated by enabling on-line reaction monitoring and adjusting the process parameters. On-line monitoring of chemical processes is a valuable tool to steer processes, leading to precise engineering of macromolecular materials. Detailed information about specific product patterns, end-group functionality or material composition can be obtained by coupling a flow reactor to a mass spectrometer (e. g. ESI-MS). In this work, we study the deprotection of maleimides and its subsequent photoenol functionalization to synthesize complex macromolecules using a photo flow reactor coupled to an ESI-MS. Using a trapping agent (TA), furan is efficiently removed from the maleimide Diels−Alder adduct within just minutes at 175 °C and quantitatively converted into an unreactive species that does not interfere with further reactions of the maleimide. The photoenol reaction was likewise shown to be highly effective to proceed in microreactors, reaching quantitative conversion of trifunctional molecules in as little as 2 min.</p

Changing the rules of the game: an analysis of EU influence on electricity and gas liberalization: with a focus on the Baltic Sea Region, and future challenges to EU energy market regulation

This study analyses the expansion of the EU into energy market regulation. It shows that the limits to EU influence and, thereby, EU energy market regulation for the internal energy market, begin where EU influence affects national interests with regard to ensuring energy security. This scientifically established insight bears an important practical implication. The further development of EU energy market regulation as a cornerstone of the internal energy market faces a particular policy challenge: It is necessary to establish a regulatory framework for the internal electricity and gas market, which acknowledges the primacy of national energy security interests. This finding is important in the light of the new and increasing energy policy challenges that some Member States face today, not least as a result of a liberalized energy market. Moreover, in the context of new systemic risks arising from ongoing energy market integration, a politically unstable (in the worst case - collapsing) EU regulatory framework can cause significant social and economic costs for individual Member States. With regard to that, the study points to the increasingly complex policy areas that are made subject to EU integration and calls for more attention to the related regulatory and political risks - also with a view to the current euro crisis. Diese Studie analysiert die Expansion der EU in die Energiemarktregulierung. Sie zeigt, dass die Grenzen des EU Einflusses und damit des EU Regulierungsrahmens für den Energiebinnenmarkt dort beginnen, wo nationale Interessen mit Blick auf die Gewährleistung der Energieversorgungssicherheit tangiert werden. Diese Erkenntnis hat eine wichtige praktische Implikation. Die weitere Ausgestaltung der EU Energiemarktregulierung und damit des Fundaments des Energiebinnenmarktes steht vor einer besonderen politischen Herausforderung: Es gilt einen stabilen gemeinschaftlichen Regulierungsrahmens für den europäischen Strom- und Gasmarkt unter dem Primat nationaler Energiesicherheitsinteressen bereitzustellen. Dies ist von Bedeutung im Lichte wachsender und neuer energiepolitischer Herausforderungen für die einzelnen Mitgliedstaaten, nicht zuletzt als Folge eines liberalisierten Energiemarktes. In Anbetracht neuer systemischer Risiken, die sich aus einem integrierten europäischen Energiemarkt ergeben, kann ein politisch instabiler (im schlimmsten Fall kollabierender) gemeinschaftlicher Regulierungsrahmen für die Mitgliedstaaten hohe soziale und ökonomische Kosten nach sich ziehen. An dieser Stelle verweist die Studie auf die immer komplexeren Integrationsgegenstände der EU und fordert, dass den damit einhergehenden Risiken, regulatorischer und politischer Art, grössere Aufmerksamkeit zu schenken ist - gerade auch mit Blick auf die aktuelle Krise der Gemeinschaftswährung