Modelling small angle neutron scattering data from polymers in supercritical fluids.

In this paper we report a SANS investigation of micelle formation by fluorocarbon-hydrocarbon block copolymers in supercritical CO[sub 2](scCO[sub 2]) at 313K. A sharp unimer-micelle transition is obtained due to the tuning of the solvating ability of scCO[sub 2] by profiling pressure. At high pressure the copolymer is in a monomeric state with a random coil structure. By lowering the pressure aggregates are formed with the hydrocarbon segments forming the core and the fluorocarbon segments forming the corona of spherical aggregates. This aggregate-unimer transition is driven by the gradual penetration of CO[sub 2] molecules toward the core of the aggregate and is critically related to the density of the solvent, thus suggesting the definition of a critical micellization density (CMD). © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]