Solubilization of alkylcyanobiphenyl liquid crystals in aqueous micellar solutions of a diblock copolymer of propylene oxide and ethylene oxide studied using dynamic and static light scattering

Abstract

The solubilization properties of P60E348 (P = oxypropylene, E = oxyethylene, subscripts = number of repeating units) diblock copolymer micelles containing liquid crystals have been studied by light scattering and UV spectroscopy for mainly dilute solutions from the following viewpoints:  (i) the micellar solubilization rate J of a nematic liquid crystal (LC), predominantly pentylcyanobiphenyl, (ii) the amount of solubilized material at saturation, and (iii) the apparent size of the P60E348 micelles containing LC and their intermicellar interaction properties. It was shown, in experiments with solubilization temperature Ts = 50 °C, that the rate J is inversely proportional to the copolymer concentration cp in the range 2 g L-1 ≤ cp ≤ 10 g L-1 whereas J is constant at higher values of cp. It was also shown that J increases strongly with an increase in temperature. The micellar hydrodynamic radius Rh was independent of temperature in the range 30 °C ≤ T ≤ 60 °C, whereas there was a reduction in the hydrodynamic virial coefficient kD and in the thermodynamic second virial coefficient A2 as T was increased (for Ts = 40 °C). To probe the intermicellar interference, the excess scattered intensity was measured as a function of cp, showing an increasing deviation from linearity, reflecting the transition from a dilute to a concentrated system and the increasing predominance of intermicellar interactions.