A combined small-angle neutron and X-ray scattering study of block copolymers micellisation in supercritical carbon dioxide

Abstract

Small angle neutron and X-ray scattering (SANS and SAXS) are used to investigate the monomer-aggregate transition of fluorocarbonhydrocarbon diblock copolymers in supercritical carbon dioxide. SANS data are analyzed using a polydisperse sphere core-shell model. Synchrotron SAXS data have been collected by profiling the pressure at different temperatures, and critical micellization densities have been obtained for a series of diblock solutions. Finally pressure jump experiments, combined with synchrotron SAXS, have revealed two steps in the dynamics of the formation of the aggregates.

Structure–Property Relationships in CO2-philic (Co)polymers: Phase Behavior, Self-Assembly, and Stabilization of Water/CO2 Emulsions

“…Using poly­( tert -butyl methacrylate) as the CO 2 -phobic block, Lo Celso et al studied the self-assembly of poly­( tert -butyl methacrylate)- b -poly­(1,1-dihydroperfluorooctyl methacrylate) (PtBMA- b -PFOMA) in sc-CO 2 at 45 °C (see Figure ). Through SAXS and SANS experiments, a transition from a random coil to a polydisperse sphere model was evidenced, suggesting the existence of a critical micelle density (CMD) in the range of 0.85–1.05 g mL –1 . The length of the CO 2 -phobic block had a greater impact on the CMD than the length of the CO 2 -philic block.…”

SANS study of the self-organization of gradient copolymers with ligand groups in supercritical CO2

“…In this article, the conformation and aggregation of three kinds of newly synthesized gradient copolymers with complexing groups are studied by SANS. SANS has been used to study polymer conformations in liquid and supercritical CO 2 [26][27][28][29][30][31][32][33][34][35] and in other supercritical fluids. 36,37 This technique is suited to study the structure of complex fluids under pressure due to the high transmission of the materials used in the construction of pressure vessels.…”

“…36,37 This technique is suited to study the structure of complex fluids under pressure due to the high transmission of the materials used in the construction of pressure vessels. Aggregation properties of several kinds of polymers (homopolymers, 28 graft 28 and block 26,27,[29][30][31][32][33][34][35] copolymers) in scCO 2 have been studied by SANS except gradient copolymers which were rarely studied by SANS, only in aqueous solutions [15][16][17] and never in scCO 2 . Several studies concern water-in-CO 2 microemulsions [38][39][40][41][42] but few were formed with polymeric surfactants.…”

Thermodynamics and Kinetic Processes of Polymer Blends and Block Copolymers in the Presence of Pressurized Carbon Dioxide

“…Variations in copolymer molecular weight appear to have little influence on the CMD. [239,240,243,248,253] Wignall has provided a detailed review of these self-organizing copolymer systems and the methods employed in their structural analysis. [256] Although novel CO 2 -philic block copolymers continue to be developed by emerging synthetic strategies, [257] the copolymers described above have thus far only been observed to form spherical micelles in the presence of scCO 2 .…”