A one-phase microemulsion composed of a hybrid fluorocarbon/hydrocarbon surfactant CyFisCHCOSOs--Na+)C7His, water, and COa solubilizes substantial amounts of water. For example, the water-to-surfactant ratio in a single phase microemulsion is as high as 32 at 25 °C and 231 bar, compared with a value near 0 for more than 150 previously studied surfactants for temperatures up to 50 °C. Also with 1.9 wt % surfactant, up to 2 wt % water is soluble, which is 10 times the amount soluble in pure CO2. The requirements for the design of surfactants that form microemulsions in CO2 are examined.
We investigate the dynamics of the lamellar-cylindrical transition in weakly segregated diblock copolymer melts. We find the limit of stability of the lamellar phase with respect to the cylindrical phase and vice versa. We consider front propagation for stable phases invading metastable phases and compute the velocity and shape of such fronts close to coexistence.
The objective of this paper is to identify the molecular parameters that govern ordering
kinetics in a diblock copolymer melt. Experimental data on the ordering kinetics were obtained by time-resolved depolarized light scattering after the sample was quenched from the disordered to the ordered
state. The ordered state consisted of cylinders arranged on a hexagonal lattice. During the early stages
of the disorder-to-order transition, a dilute suspension of ordered grains grow by invading the surrounding,
disordered phase. A time-dependent Ginzburg−Landau model was used to relate the growth rate of
these grains to molecular parameters. The growth rate is predicted to be proportional to the quench
depth and chain radius of gyration and inversely proportional to the molecular relaxation time.
Independent estimates of these parameters were obtained from small angle neutron scattering and
rheological measurements. The experimentally determined grain growth rates are in good agreement
with theoretical predictions, with no adjustable parameters.
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