Polyethersulfone structure

Membranes UF membranes consist primarily of polymeric structures (polyethersulfone, regenerated cellulose, polysulfone, polyamide, polyacrylonitrile, or various fluoropolymers) formed by immersion casting on a web or as a composite on a MF membrane. Hydrophobic polymers are surface-modified to render them hydrophilic and thereby reduce fouling, reduce product losses, and increase flux [Cabasso in Vltrafiltration Membranes and Applications, Cooper (ed.). Plenum Press, New York, 1980]. Some inorganic UF membranes (alumina, glass, zirconia) are available but only find use in corrosive applications due to their high cost. 

Polyetherimides (PEI) are polyimides containing sufficient ether as well as other flexibi-lizing structural units to impart melt processability by conventional techniques, such as injection molding and extrusion. The commercially available PEI (trade name Ultem) is the polymer synthesized by nucleophilic aromatic substitution between 1,3-bis(4-nitrophthalimido) benzene and the disodium salt of bisphenol A (Eq. 2-209) [Clagett, 1986]. This is the same reaction as that used to synthesize polyethersulfones and polyetherketones (Eq. 2-206) except that nitrite ion is displaced instead of halide. Polymerization is carried out at 80-130°C in a polar solvent (NMP, DMAC). It is also possible to synthesize the same polymer by using the diamine-dianhydride reaction. Everything being equal (cost and availability of pure reactants), the nucleophilic substitution reaction is probably the preferred route due to the more moderate reaction conditions. 

The aromatic sulfone polymers are a group of high performance plastics, many of which have relatively closely related structures and similar properties (see POLYMERS containing SULFUR, polysulfones). Chemically, all are polyethersulfones, ie, they have both aryl ether (ArOAr) and aryl sulfone (ArS02Ar) linkages in the polymer backbone. The simplest polyethersulfone (5) consists of aromatic rings linked alternately by ether and sulfone groups. 

These solvents include tetrahydrofuran (THF), 1,4-dioxane, chloroform, dichloromethane, and chlorobenzene. The relatively broad solubility characteristics of PSF have been key in the development of solution-based hollow-fiber spinning processes in the manufacture of polysulfone asymmetric membranes (see Hollow-fibermembranes). The solvent list for PES and PPSF is short because of the propensity of these polymers to undergo solvent-induced crystallization in many solvents. When the PES structure contains a small proportion of a second bisphenol comonomer, as in the case of RADEL A (Amoco Corp.) polyethersulfone, solution stability is much improved over that of PES homopolymer. 

Ultem PEI resins are amber and amorphous, with heat-distortion temperatures similar to polyethersulfone resins. Ultem resins exhibit high modulus and are stiff yet ductile. Light transmission is low. In spite of the high use temperature, they are processible by injection molding, structural foam molding, or extrusion techniques at moderate pressures between 340 and 425°C. They are inherently flame retardant and generate little smoke dimensional stabilities are excellent. Large flat parts such as circuit boards or hard disks for computers can be injection-molded to maintain critical dimensions. 

The resulting poly(oxy-1,4-phenylene sulfonyl-1,4-phenylene) (PES), CAS 25667-42-9, is a valuable polymer used to make various household appliances, medical devices, automotive parts, etc. The polymer can be shaped by thermoforming and is used in various composite materials. It has good fire safety characteristics and meets the requirements for direct food contact. Other polyethersulfones with structures similar to PES also have important practical applications and are used for the manufacturing of different appliances, cookware, automotive and aerospace components, etc. 

Polyarylsulfones are a class of high-use temperature thermoplastics that characteristically exhibit excellent thermal-oxidative resistance, good solvent resistance, hydrolytic stability, and creep resistance (10). In 1965, Union Carbide announced a thermoplastic polysulfone based on dichlorodiphenylsulfone and bisphenol A (11). This polysulfone became commercially available in 1966 and was designated as Udel polysulfone. Since 1966, Imperial Chemical Industry (ICI), Minnesota Mining and Manufacturing (3-M), and Union Carbide have commercialized polyarylsulfones that contain only aromatic moieties in the polymer structure. These materials have been designated Vlctrex polyethersulfone (ICI), Astrel 360 (3-M), and Radel polyphenylsulfone (Union Carbide). 

Membranes are designed with same base concept of resins that is, a support structure made of casted polymer (cellulose, hydrophilic polyethersulfone polyethylene, etc.) in a form of sheet rather than particles. A critical difference between the two technologies is related to the flow characteristics chromatography beads have diffusive flow with mass transfer limited by pore size and polymer structure. 

Many kinds of AEMs based on quatemized polymers containing a quaternary ammonium group have been developed and tested in ADAFC, such as polyethersulfone cardo (QPES-C) [205], polyetherketone cardo (QPEK-C) [206], poly (phthalazinone ethersulfone ketone) (QPPESK) [207], poly(arylene ethersulfone) (QPAES) [208-210], QPAES cross-linked with tetraphenylolethane glycidyl ether (QPAES/4EP) [210], poly (arylether oxadiazole) (QPAEO) [211], poly styrene-block-poly (e thy lene-ran-butylene)-block-poly styrene (QSEBS) [212], poly(vinyl alcohol) (QPVA) [213], poly(vinyl chloride) (QPVC) [214], and poly (vinylbenzyl chloride) (QPVBC) [215]. The chemical structures of some of these polymers are shown in Fig. 6.13. 

Setiawan L, Shi L, Krantz WB, Wang R. Explorations of delamination and irregular structure in poly(amide-iniide)-polyethersulfone dual layer hollow fiber membranes. J Membr Sci 2012 423 24 73-84. 

PLCs have been shown to nucleate systems which are hard to crystallize by any other means. Polyethersulfone (PES) is a high temperature thermoplastic which, even when cast from solution, is unable to crystallize [84], as opposed to, for example, PC. However, when solution blended with 30 wt% wholly aromatic longitudinal PLC (structure not reported), spherulites of the PES can be formed and it is suggested that the combined effect of solvent molecules to lubricate the motion of the crystallizing PES molecules and a nucleant (PLC) is required, either condition on its own not being sufficient. Similar attempts to crystallize the blend from the melt failed. 

With epoxy novolac and polyethersulfone (PES) modified TGAP (38), the elastic modulus was found to decrease monotonically with PES concentration, ultimate tensile strength was doubled by addition of 40% PES, and elongation to failure is also doubled at this PES concentration. Significantly, toughness decreases rapidly with diminishing volume of the phase-inverted co-continuous structure. 

H. Komber, S. Chakraborty, B. Voit, S. Baneijee, Degree of sulfonation and micro-structure of post-sulfonated polyethersulfone studied by NMR spectroscopy, Polymer 53 (2012) 1624-1631. 

Table 1. Chemical Structures and Glass-Transition Temperatures (Tg) of Polysulfone, Polyethersulfone, and Polyphenylsulfone...

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