Solubility and Self-Assembly of Amphiphilic Gradient and Block Copolymers in Supercritical CO₂

Abstract

This work aims at demonstrating the interest of gradient copolymers in supercritical CO(2) in comparison with block copolymers. Gradient copolymers exhibit a better solubility in supercritical CO(2) than block copolymers, as attested by cloud point data. The self-assembly of gradient and block copolymers in dense CO(2) has been characterized by Small-Angle Neutron Scattering (SANS), and it is shown that it is not fundamentally modified when changing from block copolymers to gradient copolymers. Therefore, gradient copolymers are advantageous thanks to their easier synthesis and their solubility at lower pressure while maintaining a good ability for self-organization in dense CO(2).

Polymer nano-foams for insulating applications prepared from CO2 foaming

“…This implies that different molecular compositions of polymers can lead to different interactions with CO 2 . The solubility of fluorinated polymers and block copolymers in compressed CO 2 has been widely investigated [75,76] because of the significant chemical interactions between fluorine-containing polymers and CO 2 . These interactions may be of a Lewis acid/base nature.…”

Asymmetric Copolymers: Synthesis, Properties, and Applications of Gradient and Other Partially Segregated Copolymers

“…Several experimental and theoretical studies have shown that gradient copolymers display substantially higher critical micelle concentrations (CMCs) than their corresponding block copolymers; amphiphilic block copolymers form aggregates more readily due to the presence of longer hydrophobic segments and greater contrast in hydrophobicity. [22,114,165,[168][169][170][171] Due to the broader distribution of monomer units along the polymer chain, the CMCs of gradient copolymers are also more sensitive to variation in hydrophobic content than those of block copolymers. [123] In aqueous solution, the cloud point (CP) temperatures of gradient copolymers are typically intermediate between those of the corresponding block and statistical copolymers.…”

“…[120] Asymmetric copolymers are more soluble in scCO 2 at lower temperature and pressure, and display lower CP pressures than related block copolymer analogs. [22,168] Interestingly, amphiphilic vinyl ester-based spontaneous gradient copolymers display faster equilibration at the water/CO 2 interface than analogous block copolymers. [22] The higher compatibility between the two polymer segments facilitates diffusion of the copolymer to the interface and also results in lower interfacial tension.…”

Micellization of St/MMA Gradient Copolymers: A General Picture of Structural Transitions in Gradient Copolymer Micelles

“…Most reported investigations mainly focused on the association behaviors of gradient copolymers . It is revealed that gradient copolymers could also form micelles the same as block copolymers but showed a better solubility in solution, leading to a higher critical micelle concentration (CMC) . Besides the unimer to micelle transition little attention was paid to other structural transitions.…”

“…[11][12][13][14][15][16][17][18][19] It is revealed that gradient copolymers could also form micelles the same as block copolymers but showed a better solubility in solution, leading to a higher critical micelle concentration (CMC). [ 16,20,21 ] Besides the unimer to micelle transition little attention was paid to other structural transitions.…”