The four tiers of structure in integrally skinned phase inversion membranes and their relevance to the various separation regimes

Abstract

SynopsisThere are four superimposed tiers of structure in integrally skinned phase inversion membranes: macromolecules (functionally submacromolecules, that is, displacements between chain segments ) ;nodules-approximately 200 A in diameter spherical macromolecular aggregates, each of which contains several tens of macromolecules (nodule interiors are denser than interstitial regimes, therefore, chain segment displacements within and between nodules differ and hence constitute a bimodal pore size distribution which may account for the dual mode sorption and permeation of gases; transport of water in reverse osmosis occurs primarily through the less dense interstitial domains); nodule aggregates-400-1000 A in diameter spherical clumps of nodules (the skins of reverse osmosis and gas separation membranes consist of a single layer of coalesced nodule aggregates; ultrafiltration pores are the spaces between incompletely coalesced nodule aggregates, and residual ultrafiltration pores are the defect pores found in reverse osmosis membranes ) ; supernodular aggregates-aggregates of nodule aggregates which constitute the walls of the 0.1-2 pm in diameter open cells in the membrane substructure ( microfiltration pores are the surface extensions of openings between adjacent cell walls).

Surface Modification of Polymeric Materials by Plasma Treatment

“…They called these structures "spheres". Recently, similar spherical structures have been observed in the skins of polysulfone gas separation membranes by Fritzsche et al 14 Figure 3 shows the permeation results obtained for the PSf membranes submitted to argon plasma treatment produced with 5 W of rf power. One can see that the permeability values decrease continuously up to 20 min of treatment, increasing again for longer times.…”

Fabrication and performance of PET mesh enhanced cellulose acetate membranes for forward osmosis

“…Before annealing, the CA nodules or CA nodule aggregates are loosely packed. Spaces between intramolecular CA chain segments (the Henry's mode sites) and large voids between nodule aggregates (the Langmuir sites) are relatively large as proposed by Kesting (1990). As the annealing temperature rises to 70°C, the voids between nodule aggregates decrease, although a certain amount of incomplete nodule aggregates still exists in some domains.…”

Synthesis and characterization of poly(amide-imide)s and their precursors as materials for membranes

“…The relationships between preparation conditions and structure and performance of the membranes have been described by several researchers. [1][2][3][4][5] The successful application of membrane technology for various separation applications depends upon the availability of high-performance membranes tailored for each specific purpose. The salient features of polymers suitable as membranes are the inherent chemical, mechanical, and thermal properties, and their processability.…”