High-Pressure Micellar Solutions of Symmetric and Asymmetric Styrene−Diene Diblocks in Compressible Near-Critical Solvents: Micellization Pressures and Cloud Pressures Respond but Micellar Cloud Pressures Insensitive to Copolymer Molecular Weight, Concentration, and Block Ratio Changes

Abstract

High-pressure solutions of polystyrene-block-polybutadiene and polystyrene-block-polyisoprene in compressible propane or propylene exhibit a robust micellar region that grows in pressure-temperature coordinates with increasing copolymer concentration, molecular weight, and styrene/diene block ratio. This happens because, while the micellization pressure strongly increases with increasing copolymer concentration, molecular weight, and styrene/diene block ratio, the micellar cloud pressure (the pressure at which the micelles aggregate and precipitate from solution) is largely insensitive to these variables. In other words, neither the block size nor the block ratio nor the copolymer concentration seems to affect much the copolymer separation from solution in the micellar region.

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

“…This is consistent with the block ratio effects on MCP recently reported for hydrogenous copolymers. 3 For the record, hydrodynamic micelle diameters measured for the deuterated and hydrogenous copolymers discussed in this section fall within a 60-70 nm range for the symmetric diblocks, S-B(37-36) and dS-dB(42-41), and within a 110-130 nm range for the asymmetric diblocks with a long Table S4 in Supporting Information, but more data are needed to analyze the deuteration effect on micelle diameters, if any.…”

“…This is because it is the styrene block that dominates MP. 3 Partially Deuterated Diblocks: Styrene-(Deuterated Diene). Figure 10 illustrates micellization pressures and micellar cloud-pressures measured for a polystyrene-block-(deuterated polybutadiene), S-dB(37-37), solution in propane.…”

“…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.…”

Can computational approaches aid in untangling the inherent complexity of practical organic photovoltaic systems?

“…Comparison of one P3HT/PCBM system to another may indeed be difficult if the polydispersity (P3HT/PCBM is not a binary system) is not the same. Even small variances in PDI can cause broad morphology changes 35,36 as well as introduce other local modifications that can lead to complex phenomena like jamming and nonFickean diffusion. 37 Altogether, a thin film of P3HT/PCBM presents an inherent heterogeneous multicomponent material structure.…”