Water-in-Water Emulsions Based on Incompatible Polymers and Stabilized by Triblock Copolymers–Templated Polymersomes

• Published in: Langmuir Vol. 29; no. 48; pp. 14804 - 14814
• Main Authors: Buzza, D. Martin A, Fletcher, Paul D. I, Georgiou, Theoni K, Ghasdian, Negar
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 03-12-2013
• Subjects: Chemistry; Colloidal state and disperse state; Emulsions. Microemulsions. Foams; Exact sciences and technology; General and physical chemistry; Water; Polymer; Triblock copolymer; Emulsion; Template
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la403356j

Aqueous solutions containing a mixture of polyethylene glycol (PEG) and dextran homopolymers form an aqueous two-phase system which can be emulsified to give a water-in-water emulsion. We show how these emulsions can be stabilized using triblock polymers containing poly[poly(ethylene glycol) methyl ether methacrylate] (PEGMA), poly (n-butyl methacrylate) (BuMA), and poly[2-(dimethylamino) ethyl methacrylate] (DMAEMA) blocks of general structure Pp-Bb-Dd, in which the middle BuMA block is hydrophobic. Low-energy input stirring of mixtures containing equal volumes of PEG- and dex-rich aqueous phases plus 1 wt % of Pp-Bb-Dd stabilizer all form dex-in-PEG emulsions (for the range of Pp-Bb-Dd triblock polymers used here) which have a polymersome-like structure. In favorable cases, the emulsion drop (or templated polymersome) sizes are a few micrometers and are stable for periods in excess of 6 months. The emulsions can be inverted from dex-in-PEG to PEG-in-dex by increasing the volume fraction of dex-rich aqueous phase. We demonstrate that both high and low molecular weight fluorescent solutes “self-load” into either the dex- or PEG-rich regions and that solute mass transfer across the water–water interface occurs on a timescale of less than 1 min.