Synthesis and characterization of solution-processable polyelectrolyte complexes and their homogeneous membranes.

Solution-processable polyelectrolyte complexes (PECs) between poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) were synthesized in aqueous NaOH and obtained in their solid forms by protection and deprotection of carboxylic acid groups. Elemental analysis, conductance measurement, and FT-IR showed that the composition and ionic complexation degree (ICD) of the PECs can be controlled effectively by tuning the NaOH concentration in both parent polyelectrolyte solutions. Thermal gravity analysis showed that PECs revealed good thermal stability, and differential scanning calorimetry showed that the glass transition temperature (Tg) of PECs increased with increasing ICD and finally became undetectable when ICD was above 0.16. Viscosity properties of the PEC solutions were well correlated to the ICD of PECs, and it was found that solid PECs could be redissolved in dilute NaOH without breaking the ionic complexation between PDDA and PAA. Homogeneous PEC membranes (HPECMs) were made from their concentrated solutions, and their morphologies were examined by field emission scanning electron microscopy. These novel HPECMs were subjected to dehydration of organics for the first time, and a very promising performance was obtained. Furthermore, another two solution-processable PECs between weak anionic polyelectrolyte and cationic polyelectrolyte were also synthesized by the same method and showed a very high separation performance.