Interdomain spacing, d, of microphase-separated poly(styrene-b- dimethylsiloxane) in high-pressure carbon dioxide (CO2) was found to follow a modified power law scaling, d/ξ ∼ φdiblock -γ, where ξ is a swelling asymmetry factor and φdiblock; is the volume fraction polymer. This interdomain spacing was measured in situ both isothermally and at constant φdiblock using small-angle neutron scattering. The use of high-pressure CO2 as the diluent enabled precise control of sorbed solvent volume fraction in highly concentrated systems at elevated temperatures. Data measured at constant φdiblock are in agreement with theoretical predictions and experimental data for dilution by traditional liquid solvents and follow the scaling law d ∼ χAB -β. In the highly concentrated regime, the isothermal dependence on φdiblock cannot be described by the simple power law scaling previously suggested for liquid diluents, d ∼ φpolymer -γ. By accounting for solvent selectivity using ξ, however, d-spacing as a function of φdiblock for a system exhibiting lamellar morphology collapses to a common scaling.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry