Emulsions were used to overcome problems with printing highmolecular-weight polymers in solution. A polymer is dissolved in an oil and dispersed in a surfactant solution. The surface tension of the oil/water interface opposes deformation of the oil droplets and thus the polymer chains are shielded from the high extensional strain rates that occur during inkjet printing. Consequently the elasticity of polymers under strain that inhibits jetting of pure polymer solutions is circumvented. The exemplar system is a 40 %wt discontinuous phase comprising a 9.5 %wt methyl benzoate solution of polystyrene (initial Mn = 487 kDa) dispersed in a 14.8 mM SDS solution. Drops were printed from a 50-μm nozzle and the drying process followed with a high-speed camera. The relative vapor pressure of the continuous and discontinuous phases is an important parameter in the drying process. Best results were obtained when the water evaporated first to leave a spherical cap of the polystyrene solution in oil. Limitations of the use of emulsions to print polymers are discussed.
Ashley S. Johns, Colin D. Bain, "Using emulsions to overcome problems associated with the inkjet printing of high-molecular-weight polymers in solution" in Proc. IS&T Int'l Conf. on Digital Printing Technologies and Digital Fabrication (NIP31), 2015, pp 476 - 480, https://doi.org/10.2352/ISSN.2169-4451.2015.31.1.art00105_1