Tough, dense polyelectrolyte complexes (PECs) with well-defined cross-sections are prepared using a laboratory extruder and plasticizing the complexes with salt water. Stoichiometric starting materials yield stoichiometric complexes of poly(diallyldimethylammonium) (PDADMA) and poly(styrene sulfonate) (PSS). As an example of this enabling technology, macroscopic tubes of PEC are produced. Microscopy images of cross-sections of rods, tape, and tubes show a pore volume of less than 10% in the bulk of the extruded complex and fully dense material towards the surface, where the shear is greatest. Thermal gravimetric analysis reveals the expected salt content for PECs doped with NaCl, and a lack of salt for PECs rinsed in water. The fact that doped PECs are transparent suggests they are supersaturated with salt. Residual stress following extrusion is relieved by exposure to solutions of NaCl. Stress relaxation experiments show decreasing equilibrium moduli as a function of increasing salt doping, consistent with prior results on multilayers of the same polymers.
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