Conformational features of poly(1,1-dihydroperfluorooctyl acrylate) and poly(vinyl acetate) diblock oligomers in supercritical carbon dioxide

Abstract

We report detailed molecular dynamics calculations of single chain diblocks of poly(1,1- dihydroperfluorooctyl acrylate) (PFOA) and poly(vinyl acetate) (PVAc) in supercritical carbon dioxide, SCCO2. At the critical micelle concentration, this system exhibits self-assembly into micellar structures due to the solvent specific selectivity of the blocks. Although the intermolecular factors determining micelle formation are well studied for this system, the intramolecular single chain conformational features of the molecules have not yet been investigated in the literature. The specific aim of the present work is to study the conformational properties of the single diblock chains in supercritical carbon dioxide at 65 °C, and at four different pressures by molecular dynamics simulations. Fluctuations in the shapes of the PVAc and PFOA blocks are observed to be strongly dependent on pressure. The rate of approach of an initially rodlike chain to its equilibrium conformational space is likewise found to depend strongly on pressure. Calculations of the radial distribution function for the solvent molecules around the chain show that a solvation shell is formed around the polymer. Important correlations between the results of single chain calculations and micelle behavior are observed and discussed.

Macromolecular surfactants for supercritical carbon dioxide applications: Synthesis and characterization of fluorinated block copolymers prepared by nitroxide‐mediated radical polymerization

“…As shown in Figure 4, at a given temperature, higher pressure (i.e., higher CO 2 density) is needed to solubilize the block copolymers in comparison with the fluorinated homopolymers. This behavior is in qualitative agreement with theory because the presence of the CO 2 ‐phobic block is expected to increase the cloud point pressure 58, 59. Because PS is essentially insoluble in neat CO 2 ,8 the phase behavior of the soluble block copolymers indicates the formation of micelles with PFDS or PFDA in the outer shell and PS in the core.…”

Self-assembly of surfactants in a supercritical solvent from lattice Monte Carlo simulations

“…Salaniwal et al [6][7][8] studied selfassembly of micelles in scCO 2 -dichain surfactant-water systems by molecular dynamics simulations with an atomistic model. Baysal et al 9 performed molecular dynamics calculations with an atomistic model to study the conformational properties of single chain diblocks of poly͑1,1dihydroperfluorooctyl acrylate͒ and poly͑vinyl acetate͒ in scCO 2 . Luna-Bárcenas et al 10 used the statistical associating fluid theory 11 to model phase behavior in scCO 2 -poly͑FOA͒ systems and Colina et al 12 combined the osmotic pressure approach with the statistical associating fluid theory to study phase diagrams of copolymers in scCO 2 .…”

Formation of Spherical Micelles in a supercritical Solvent: Lattice Monte Carlo Simulation and Multicomponent Solution Model

“…Salaniwal et al [6 -8] studied self-assembly of micelles in scCO 2 -dichain surfactant -water systems by molecular dynamics simulations with an atomistic model. Baysal et al [9] performed molecular dynamics calculations with an atomistic model to study the conformational properties of single chain diblocks of poly(1,1-dihydroperfluorooctyl acrylate) and poly(vinyl acetate) in scCO 2 . Luna-Bárcenas et al [10] used the statistical associating fluid theory [11] to model the phase behavior of scCO 2 -poly(FOA) systems and Colina et al [12] combined the osmotic pressure approach with the statistical associating fluid theory to study phase diagrams of copolymers in scCO 2 .…”