Synthesis of poly(ethylene-co-butylene)-block-poly(ethylene oxide) surfactant and its use in the synthesis of polyhydroxyethyl methacrylate nanoparticles containing azo-dye

Abstract

A synthetic path to poly(ethylene-co-butylene)-block-poly(ethylene oxide), a substitute for the “KLE” surfactant was developed. For this purpose, mono hydroxyl end-functionalized poly(ethylene-co-butylene) (∼3800 g mol⁻¹) was modified with a triple bond at its hydroxyl group, while two samples of mono hydroxyl end-functionalized poly(ethylene oxide) (∼2000 g mol⁻¹ and 5000 g mol⁻¹) were modified with an azide group. The two blocks were bound together by click chemistry and the products characterized by ¹H NMR spectroscopy, EA and GPC. The ability of these new block copolymers to stabilize nanodroplets in inverse miniemulsion polymerization of 2-hydroxyethyl methacrylate (HEMA) was investigated. It was found that the molecular weight of the poly(ethylene oxide) block strongly influences the stability of the miniemulsions; only the copolymer with the short oligoethylene block gave satisfactory results. The possibility of encapsulating Disperse Red 1 (DR1) dye in polyhydroxyethyl methacrylate (PHEMA) was also investigated and the miniemulsions were optimized such as to prepare particles with a maximum DR1 loading of approximately 21 wt%. To avoid dye agglomeration and phase separation during polymerization, DR1 was equipped with a polymerizable group. The resulting particles were characterized by DLS, SEM, TGA, UV-vis and DSC. These particles are of importance as fillers in polydimethylsiloxane composites that are used as electrostrictive materials.