Liquid-liquid phase separation (LLPS) is an important phenomenon that has been extensively investigated for proteins and polymers solutions due to its applications in the fields of material and separation science and biotechnology. LLPS of macromolecular solutions can be induced by changing physicochemical properties such as temperature, ionic strength and solvent quality. In this work, we explore the ability of aqueous solutions of dendrimers to undergo LLPS. These are synthetic hyperbranched macromolecules with interesting structural properties that make them very appealing for applications such as host-guest chemistry and self-assembly. To our knowledge, no experimental investigation on LLPS has been reported for dendrimer solutions. In this work we show that aqueous solutions containing fourth generation poly(amido amine) (PAMAM) dendrimers with amine (PAMAM-NH2) or hydroxyl (PAMAM-OH) functionalized surfaces undergo temperature-induced LLPS in the presence of sodium sulfate. We experimentally characterize the effect of mixture composition on the LLPS temperature and the composition of the coexisting phases at constant temperature (dendrimer/salt partitioning). In the case of PAMAM-NH2, LLPS is induced by lowering temperature. Interestingly, our results for the PAMAM-OH case revealed that the observed phase transition switches from being induced by lowering temperature to being induced by increasing temperature as the salt concentration increases. This behavior is unique and fundamentally different from that observed for polymers and protein systems. To describe the observed experimental behavior, we developed a model based on steric interactions and salt-induced preferential hydration of dendrimers. Our investigation provides guidance for applications of dendrimers in liquid-liquid partitioning methods relevant to host-guest chemistry and separation science, and the preparation of dendrimer-based materials obtained from the coacervation of these macromolecules.

Liquid-liquid phase separation of dendrimer aqueous solutions

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.