High-Pressure Micellar Solutions of Polystyrene-block-polybutadiene and Polystyrene-block-polyisoprene in Propane Exhibit Cloud-Pressure Reduction and Distinct Micellization End Points

Abstract

Micellar solutions of polystyrene-block-polybutadiene and polystyrene-block-polyisoprene in propane are found to exhibit significantly lower cloud pressures than the corresponding hypothetical nonmicellar solutions. Such a cloud-pressure reduction indicates the extent to which micelle formation enhances the apparent diblock solubility in near-critical and hence compressible propane. Concentration-dependent pressure-temperature points beyond which no micelles can be formed, referred to as the micellization end points, are found to depend on the block type, size, and ratio. The cloud-pressure reduction and the micellization end point measured for styrene-diene diblocks in propane should be characteristic of all amphiphilic diblock copolymer solutions that form micelles in compressible solvents.

Amorphous polystyrene-block-polybutadiene and crystallizable polystyrene-block-(hydrogenated polybutadiene) solutions in compressible near critical propane and propylene – Hydrogenation effects

“…The micellization in propylene is at least 300 bar lower than that in propane. More subtle cloud-point and micellization phenomena for this S-B copolymer observed at higher temperatures, above 170°C in propane and above 140°C in propylene, as these systems approach a critical micellization temperature, are being documented in a separate project [22].…”

“…This is because the polybutadiene block in S-B may thermally decompose at higher temperatures, as explained in Ref. [22].…”

Deuteration Impact on Micellization Pressure and Cloud Pressure of Polystyrene-block-polybutadiene and Polystyrene-block-polyisoprene in Compressible Propane

“…The copolymer cloud-pressure curve consists of two distinct branches, a conventional cloud-pressure (CP) branch above the micellar end point (MEP, a pressure-generalized critical micelle temperature) and a micellar cloud-pressure (MCP) branch below MEP. 2 At CP, we observe the onset of copolymer precipitation upon decompression of a random nonmicellar solution. At MCP, we observe the onset of copolymer precipitation upon decompression of a micellar solution.…”

“…At MCP, we observe the onset of copolymer precipitation upon decompression of a micellar solution. The previous work demonstrated that MCP is consistently lower than CP estimated for a hypothetical random solution 2,3 and that it is not very sensitive to the diblock molecular weight, composition (block ratio), or concentration. This is in contrast to the micellization pressure (MP), which depends on the diblock molecular weight, composition (block ratio), and concentration.…”

Polystyrene‐block‐Polyisoprene Diblock‐Copolymer Micelles: Coupled Pressure and Temperature Effects

“…In comparison with the impact of temperature, the effects of pressure on micellization of block copolymers have been less explored, in part due to difficulties in sample environments . Previous studies utilize supercritical CO 2 (scCO 2 ), near‐critical propane, near‐critical trifluoromethane, and dimethyl ether, and so on to manipulate micellization of block copolymers. The solvent quality in these studies varies largely with pressure since they are highly compressible within the accessible experimental window.…”