Phase behavior and rheological properties of polyamine-rich complexes for direct-write assembly.

Polyamine-rich complexes are developed for microscale patterning of planar and 3-D structures by direct ink writing. The complexes are formed by mixing poly(allylamine) hydrochloride and poly(acrylic acid) sodium salt in water in a nonstoichiometric ratio. Their phase behavior, rheological properties, and coagulation behavior in alcohol-water reservoirs are characterized. Direct comparisons are made between these complexes, which are based on mixtures of linear polyelectrolytes, and prior observations of complexes composed of linear and highly branched chains. [Gratson, G. M.; Xu, M.; Lewis, J. A. Nature 2004, 428, 386. Gratson, G. M.; Lewis, J. A. Langmuir 2005, 21, 457-464.] The optimal polyamine-rich ink and reservoir compositions are identified for direct-write assembly of wavy, gradient, and 3-D microperiodic architectures.