Atomistic models of three fluorinated polyimides in the amorphous state

Abstract

Molecular models of three fluorinated polyimides based on the 4,4′‐(hexafluoroisopropylidene)diphthalic dianhydride (6FDA) have been studied using molecular dynamics (MD) simulations. The respective diamines were 4,4′‐hexafluoroisopropylidene dianiline (6FpDA), 3,3′‐hexafluoroisopropylidene dianiline (6FmDA), and 2,4,6‐trimethyl‐1,3phenylenediamine (DAM). Thirty independent samples were prepared using a hybrid pivot Monte Carlo‐MD generation technique and average densities were found to be in very good agreement with experiment. Model structures also agreed with available wide‐angle X‐ray scattering data. Cohesive energies, Hildebrand solubility parameters, fractional free volumes (FFV), void space distributions and intermolecular as well as intramolecular interactions were analyzed. The differences in bulk properties between both 6FDA‐6FpDA and 6FDA‐6FmDA isomers remain fairly small, although the configurations of the former are more extended. 6FDA‐DAM has a lower density, larger intermolecular distances, and higher free volume than the other two polyimides. Results are discussed with respect to their use as matrices for gas separation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1166–1180, 2009

Effects of aromatic regularity on the structure and conductivity of polyimide‐poly(ethylene glycol) materials doped with ionic liquid

“…The R groups of polyimides often contain hexafluoro groups between two aromatic rings. Because of the bulky and relatively flexible nature of these hexafluoro bridging groups, the polymer chains tend not to have any regularity or order in their packing or positioning . Some partially or non‐fluorinated polyimides, where either R1 or R2 contain less bulky groups and have more aromatic character, have been shown to possess new structural features as compared with the fully fluorinated polyimides.…”

Influences of liquid electrolyte and polyimide identity on the structure and conductivity of polyimide–poly(ethylene glycol) materials

“…Polyimides, both with and without PEG, have been studied previously and have been found to exhibit differences in structural order, interactions, and free volume, which can impact behavior and properties. These material variations can be achieved through the specific choice of aromatic monomers . In this work, protic liquids, including ionic liquids, have been incorporated into some of the polymer membranes in order to provide the ion conduction capability, both the membrane ion source and vehicle, so polymer–ionic liquid interactions are expected to influence performance.…”

A comparison of homopolymer and block copolymer structure in 6FDA-based polyimides

“…37,38 A number of simulation studies were directed towards the thermal and mechanical properties of polyimides [39][40][41][42][43][44][45][46] whereas several others have focused on structural and bulk characteristics. [47][48][49][50][51][52] However, to our knowledge, structural and void space features of block copolyimides have not been examined at the molecular level in contrast to their base homopolyimides.…”