Facile synthesis and surface activity of poly(ethylene glycol) star polymers with a phosphazene core

Abstract

A series of PEG-based star polymers with hexa(eugenol) cyclotriphosphazene (HECTP) core and controlled number of PEG arms have been prepared in high yields via simple thiol-ene click reaction combining Dicyclohexylcarbodiimide/4-Dimethylaminopyridine (DCC/DMAP) esterification under very mild experimental conditions, and their potential for application as surfactants was investigated. The surface activities, including the critical micelle concentration (CMC) and surface tension at CMC, of the polymer aqueous solutions were studied. The results showed that PEG-based star polymers with two arms have good surface activities such as low surface tension (low to 36.1 mN/m), good emulsification ability, due to their structural features similar to Gemini surfactants. Whereas, the PEG-based star polymers with more than two arms exhibited very low CMC values (low to 0.004 mg/ml) and strong emulsification ability, therefore they could be utilized as surfactants to form high internal phase emulsions (HIPEs). Using these new PEG-based star polymers as surfactants, a very low surfactant concentration (0.01 wt %) was sufficient to form oil-in-water emulsions with long-term stability more than 6 months. Although further studies are necessary to clarify the interfacial properties, this work opens a new study field for this kind of important organic-inorganic hybrid materials.