High Throughput Measurements of Polymer Fluids for Formulations *
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High Throughput Measurements of Polymer Fluids for Formulations* Kathryn L. Beers, João T. Cabral, Howard J. Walls and Eric J. Amis Polymers Division, National Institute of Standards and Technology Gaithersburg, MD 20899-8542, USA ABSTRACT Rapid prototyping of microfluidic handling devices has gained popularity due to the ability to quickly test and modify new design features several times in one day. At the NIST Combinatorial Methods Center (NCMC), we have modified common microfluidic fabrication techniques to extend their use to organic fluids. Ultraviolet (UV) curable adhesives were used to create molded resins with increased solvent resistance. This has allowed the preparation of new types of combinatorial libraries and development of new measurement methods to complement the small sample sizes of these libraries. Most importantly, it can be used to tie together multiple stages of the formulation process, from the synthesis of polymers to the measurement of complex-fluid properties, in small and inexpensive platforms. Our first demonstrations of this technology are in the areas of emulsions and polymer blends. Measurement techniques include light and x-ray scattering and rheology. Milli-fluidic handling and measurements will increase the dimensions of parameter space that are available to accurate and systematic study of polymer solutions. These capabilities will also enable the generation of new information in the field of polymer formulations, which is presently dominated by empirical knowledge. INTRODUCTION Advanced materials development in areas as varied as personal care, construction and tissue engineering require new approaches to quickly acquire large quantities of reliable data on complicated multi-component mixtures. Considerable attention has been placed on generating large sample libraries for testing material properties. Successes in catalyst discovery and polymer synthesis are good examples of the value in this approach. There are problems, however, where high-resolution control of the composition of a mixture is required. For example, in polymer formulation slight changes in the fraction of added compatibilizer or the molecular mass of the copolymer added to a polymer blend have dramatic impact on phase morphologies and kinetics. While existing methods can still be useful in these situations, staggeringly large sample sets would be required to prepare libraries which reflected both the large and small scope problems faced by formulation scientists. To complement the static library approach, we are interested in developing methods to continuously change and measure fluid composition and properties. Besides combinatorial methods, another technology developed for application in the life sciences has also drawn attention from multiple materials science disciplines: microfluidics, also called lab-on-a-chip or micro-total-analytical-systems (µTAS).[1] These small devices contain channels carved into silicon, glass or polymer platforms, through which fluids are pumped, mixed, reacted and analyze
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