We demonstrate the use of accelerated reactions with desorption electrospray ionization mass spectrometry (DESI-MS) as a tool for predicting the outcome of microfluidic reactions. DESI-MS was employed as a high throughput experimentation tool to provide qualitative predictions of reaction outcomes, so that vast regions of chemical reactivity space may be more rapidly explored and areas of optimal efficiency identified. This work is part of a larger effort to accelerate reaction optimization to enable the rapid development of continuous-flow syntheses of small molecules in high yield. In order to build confidence in this approach, however, it is necessary to establish a robust predictive connection between reactions performed under analogous DESI-MS, batch, and microfluidic reaction conditions. In the present work, we explore the potential of high throughput DESI-MS experiments to identify trends in reactivity based on chemical structure, solvent, temperature, and stoichiometry that are consistent across these platforms. N-alkylation reactions were used as the test case due to their ease of reactant and product detection by electrospray ionization mass spectrometry (ESI-MS) and their great importance in API synthesis. While DESI-MS narrowed the scope of possibilities for reaction selection among some parameters such as solvent, others like stoichiometry and temperature still required further optimization under continuous synthesis conditions. DESI-MS high throughput experimentation (HTE) reaction evaluation significantly reduced the search space for flow chemistry optimization, thus representing a significant savings in time and materials to achieve a desired transformation with high efficiency.
Sulfonated poly(arylene ether phosphine oxide)s with various distributions and contents of pendant sulfonic acid groups were synthesized through direct polycondensation. The microscopic structure of their corresponding membranes was well controlled by tuning the distribution and content of sulfonic acid side groups while their polymer backbones remained unchanged. As a result, the simultaneous improvement of their proton conductivity and oxidation resistance as well as dimensional stability was realized, which was very difficult for hydrocarbon proton exchange membranes (PEMs). Meanwhile, the resulting membrane showed outstanding overall properties such as a swelling close to that of Nafion 117 and 1.6 times the proton conductivity of Nafion 117. Moreover, it showed the best oxidative stability among the hydrocarbon PEMs with approximate proton conductivity so far.
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