Polymer fluids future directions

Although essentially all studies to date using PRISM and the molecular closures have involved macromolecules, it is conceivable such closures may be of value even for small or intermediate-sized flexible and/or rigid molecules. A careful documentation of the accuracy of the new molecular closures as a broad function of thermodynamic state and molecular fluid type remains an important future direction. In addition, recent interesting alternative approaches to liquid theory for polymer mixtures with attractions have been developed within the general PRISM framework by Melenkevitz and Curro based on the optimized RPA(ORPA) approach, and Donley et. ah " based on density functional theory and also from a field-theoretic perspective by Chandler. Application of these approaches to treat the effect of attractive interactions on fluid structure and phase transitions remains to be worked out. 

Polymeric microfluidic systems coupled to a microfabricated planar polymer tip can be used as a stable ion source for ESI-MS. A parylene tip at the end of the microchannel delivers fluid which easily produces a stable Taylor cone at the tip via an applied voltage. The described device appears to facilitate the formation of a stable spray current for the electrospray process and hence offers an attractive alternative to previously reported electrospray emitters. When this interface was employed for the quantification of methylphenidate in urine extracts via direct infusion MS analysis, this system demonstrated stable electrospray performance, good reproducibility, a wide linear dynamic range, a relatively low limit of quantification, good precision and accuracy, and negligible system carryover. We believe polymeric devices such as described in this report merit further investigation for chip-based sample analysis employing electrospray MS in the future. 

How will the method develop in the future This is of course difficult to predict. However, it seems clear that there will be two main directions, a further development of the method itself, and its application to new problems in Soft Matter hydrodynamics. On the methodological front, there are several very recent developments, like angular-momentum conservation, multi-phase flows and viscoelastic fluids, which have to be explored in more detail. It will also be interesting to combine them to study, for example, multi-phase flows of viscoelastic fluids. On the application side, the trend will undoubtedly be towards more complex systems, in which thermal fluctuations are important. In such systems, the method can play out its strengths, because the interactions of colloids, polymers, and membranes with the mesoscale solvent can all be treated on the same basis. 

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