Solubilization of alkylcyanobiphenyls in aqueous micellar solutions of a diblock copolymer of propylene oxide and ethylene oxide

A diblock copolymer of propylene oxide and ethylene oxide, denoted Py4E316, was prepared by sequential anionic polymerization of the two monomers. C-1 3 NMR spectroscopy was used to obtain the absolute number-average molar mas s and overall composition (whence the molecular formula), and gel permeatio n chromatography was used to confirm a narrow chain-length distribution. A number of techniques (light scattering, dye solubilization with DPH (1,6-di phenyl-1,3,5-hexatriene), surface tension) were used to confirm micellizati on in dilute aqueous solution and to determine the temperature dependence o f the critical micelle concentration. Light scattering was also used to det ermine the temperature dependence of micellar association number and radius . Copolymer solutions of concentration 10 and 20 g dm(-3) copolymer were us ed to solubilize a nematic liquid crystal mixture with a wide nematic range , coded BL002. The extent of solubilization in the temperature range 20-40 degreesC could be correlated with the extent of micellization of the copoly mer, leading to an upper limit at 40 degreesC of ca. 50 mg (g of copolymer) (-1), i.e., 180 mg (g of hydrophobe)(-1). It was noted that BL002 solubiliz ation could be adapted to provide a method for determining the critical mic elle temperatures of aqueous solutions of the copolymer.