| Abstract
| - The phase behavior of nearly symmetric styrene−isoprene (SI) diblock copolymers in thepresence of compressed CO2 or ethane was studied using small-angle neutron scattering. Sorption ofeither fluid depresses the upper order−disorder transition (UODT) by as much as 55 °C at fluid densitiesof less than 0.35 g/cm3. The solvent-induced transitions are fully reversible upon fluid desorption. Themagnitude of the depression can be controlled by manipulating the mass fraction of fluid sorbed throughpressure-mediated adjustments in solvent density. Consequently, the location of the UODT can be tunedover broad ranges, and the state of segregation can be controlled via isothermal adjustments in totalsystem pressure. The influence of hydrostatic pressure, inherent to the use of compressed solvents, issmall in comparison to the solvent effect over the range of pressures studied.
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