Polysulfones and Poly ether sulfone

14 Synthesis of poly(ether suIfone)s by (a) Friedel Crafts sulfonylation. (b) nucleophilic polycondensation in solution using phenolates. and (c) melt polycondensalion using trimethylsilyl derivatives of bisphenols. 

While the former reaction bears the risk of side reactions, namely, sulfonylation not only in ara-position but also in orf/io-position, the latter gives only the desired linear all-para product. 

PSU and PES have been widely used as membrane materials for ultrafiltrafion, pervaporation [216-218], or electrodialysis [219], due to their chemical and thermal stabilities, high glass transition temperature (Fg), which is in the range of 180 °C to values well above 200 °C, and good film-forming properties and solubility in dipolar aprotic solvents, such as NMP, DMAc, or DMSO. Besides the classical poly(ether sulfone) (Fig. 3.14a) derived from the reaction of 4,4 -dihalodiphenylsulfone and 4,4 -hydroxydiphenylsulfone or self-condensation of 4-halo-4 -hydroxydiphenylsulfone and polysulfone (Fig. 3.14b) derived from the reaction of bisphenol A (2,2-bis(4-hydroxyphenyl)propane) and 4,4 -dihalodiphenylsulfone, a large number of polysulfones have been either commercialized or prepared for research purposes by variation of the bisphenol moieties. 

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Sulfonation and Phosphonation of Polysulfones and Poly(ether sulfone)s... 

Dialysis involves diffusion of solutes and fluids (e.g., water) through a semipermeable membrane separating out larger molecules and solid particles. Hie membranes employed are generally similar to the reverse osmosis or the nano-/ ultrafiltration type. Historically, dialysis has heen employed for various laboratory separations and commercially employed for NaOH or dilute sulfuric add recovery. The primary com-merdal application involves hemodialysis employed in artifidal kidney machines. Initially, cellulose and cellulose acetate membranes were employed, but polysulfone and poly (ether sulfone) are now in use with biocompatibiUty being a key membrane requirement. 

Recendy, Guiver et al. reported a number of derivatives of polysulfone and poly(aryl sulfone).172 188 Polysulfones were activated either on the ortho-sulfone sites or the ortho-ether sites by direct lithiation or bromination-lithiation. The lithiated intermediates were claimed to be quantitatively converted to azides by treatment with tosyl azides. Azides are thermally and photochemically labile groups capable of being transformed readily into a number of other useful derivatives. 

Typical UF membrane materials are polysulfone (PS), poly ether sulfone (PES), polyetheretherketone (PEEK), cellulose acetate (CA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyimide (PI), and polyetherimide (PEI) ... 

Membrane permeation properties are largely governed by the pore sizes and the pore size distributions of UF membranes. Rather, thermal, chemical, mechanical, and biological stability are considered of greater importance. Typical UF membrane materials are polysulfone (PS), poly(ether sulfone), poly(ether ether ketone) (PEEK), cellulose acetate and other cellulose esters, polyacrylonitrile (PAN), poly(vinyKdene fluoride) (PVDF), polyimide (PI), poly(etherimide) (PEI), and aliphatic polyamide (PA). All these polymers have a Tg higher than 145 °C except for celliflose esters. They are also stable chemically and mechanically, and their biodegradabflity is low. The membranes are made by the dry-wet phase inversion technique. 

In another study, Bowen et al. [42] prepared membranes from polymer blends of polysulfone and sulfonated poly(ether ether ketone) (PSf/SPEEK). It was reported that these membranes had high porosities, high charge densities, and pore sizes at the boundary between NF and UE For comparison, two commercial membranes of cellulose acetate and poly(ether sulfone) were chosen. Therefore, the following four membranes were involved in their study ... 

Poly(ester urethane) and poly(ether sulfone) blends with or without Thermal degradation of blends using TGA The presence of polysulfone caused a rise in thermal stability of the Filip and Vlad 2004... 

Figure II i9. The chemical souctures of polysulfone (PSf) and poly(ether sulfone) (PES)...

Typical PHB spectra of quinizario and tetraphenylporphin in various polymer matrices at 4 K are shown in Fig. 19. For quinizarin, narrow and stable holes are formed in PMMA and poly(vinyl alcohol) ffVA), while the hole formation is less marked in polycarbonate (PC), polysulfone (PSF), poly(ether sulfone) (PKF), and aromatic polyimide (PI) These facts suggest that the change in hydrogen bond from intramolecular to intermolecular is a key reacticm for the PHB of quinizarin and... 

The effect of moisture on the p relaxations in amorphous phenylene polymers is well documented (Allen et al. 1971 Lim et al. 1973 Chung and Sauer 1971). For example, Allen et al. (1971) determined that both the mechanical and dielectric P relaxations in polysulfone, polycarbonate, poly(phenylene oxide), and poly (ether sulfone) were dependent on the water content of the samples as illustrated for polysulfone in Fig. 5.31. In addition, the amount of water absorbed depended on the polarity of the molecule. The results indicate that the absorbed water hydrogen bonds to polar groups along the polymer chain and, as such, takes part in the molecular processes that give rise to the P relaxation. This is consistent with the other examples cited previously. 

Meanwhile, most commercial polysulfones (PSU) and poly(ether sulfone)s (PES) are obtained from conversion of suitable aromatic dihalides with bisphenols by nucleophiUc displacement polycondensation (Fig. 19B). Generally, 4,4 -dichlorodiphenyl suUbne (DCDPS) is reacted with alkali salts of bisphenols [92,93]. The reaction is carried out in solution using hT-methyl-2-pyrrolidone (NMP), N,N-dimethyl acetamide (DMAc), or dimethyl sulfoxide (DMSO) as the solvent. Occasionally, the more reactive, but also more expensive, 4,4 -difluorodiphenyl sulfone might be used for experimental purposes. Usually, the electronegativity of the sulfone Unkage is sufficient to increase the reactivity of the aromatic chloride in DCDPS (Fig. 19). 

The temperature dependence of the ultrasonic velocity (Figure 15), normalized to the glass transition temperature, indicates that both polycarbonate and poly(ether sulfone) possess similiar molecular relaxation characteristics. In contrast, polysulfone either has a much higher sound velocity (modulus) in the rubbery state or (as is more likely) undergoes another relaxation (with associated decrement in the sound velocity) between 363 K and the glass transition. This is probably a consequence of partially crystalline structure existing in the solid at room temperature. 

Polysulfone (PSU) is a family of thermoplastic polymers they are classified as PSU, poly(aryl sulfone), and poly(ether sulfone) (PES) by the polymer backbone structure. They are well known for their toughness and stability at high temperatures (-100°C to 150°C), high oxidative stability, and dimensional stability. Hence, it is easy to get the thin membrane with reproducible properties, which have been widely used in many fields like hemodialysis, wastewater treatment, gas separation, and especially PEM fuel cell applications. 

Amorphous polymers are characterized by the following properties They are transparent and very often soluble in common organic solvents at room temperature. The following amorphous polymers have gained industrial importance as thermoplastic materials polyfvinyl chloride), polystyrene, polyfmethyl methacrylate), ABS-polymers, polycarbonate, cycloolefine copolymers, polysulfone, poly( ether sulfone), polyfether imide). 

Different TPs have been used to modify thermosets, such as poly(ether sulfone) (PES), polysulfone (PSF), poly(ether ketone) (PEK), polyether imide (PEI), poly(phenylene oxide) (PPO), linear polyimides, polyhydan-toin, etc. (Stenzenberger et al., 1988 Pascal et al., 1990, 1995 Pascault and Williams, 2000). 

Most of today s ultrafiltration membranes are made by variations of the Loeb-Sourirajan process. A limited number of materials are used, primarily polyacrylonitrile, poly(vinyl chloride)-polyacrylonitrile copolymers, polysulfone, poly(ether sulfone), poly(vinylidene fluoride), some aromatic polyamides, and cellulose acetate. In general, the more hydrophilic membranes are more fouling-resistant than the completely hydrophobic materials. For this reason water-soluble... 

Figure 18.18 Map of dielectric properties of engineering plastics. Among engineering plastics, SPS (impact modified and GF-reinforced HB and IR grades) has very low dielectric dissipation factor and dielectric constant following those of fluorocarbon polymers. PSF, polysulfone PPE, poly(phenylene ether) PES, poly(ether sulfone) PAr, polyarylate...

Polymeric materials for MF membranes cover a very wide range, from relatively hydrophilic to very hydrophobic materials. Typical hydrophilic materials are polysulfone, poly(ether sulfone), cellulose (CE) and ceUiflose acetate, polyamide, polyimide, poly(etherimide) and polycarbonate (PC). Typical hydrophobic materials are polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE, Teflon) and poly(vinylidene fluoride). 

Membrane polymers include polypropylene, poly (vinylidene difiuoride), polysulfone, poly(ether sulfone), poly(ether ether ketone), polyvinyl alcohol, polyacrylonitrile, polycarbonate, and poly(ethylene terephthalate). 

The highly intractable chemical stmcture vMch. inq)arts the outstanding mechanical properties also makes the PATs very difficult to process (4, 5). In the ftilly imidized form PAI is not processable hence a poly(amic acid) (PAA) precursor is the usual form in which they are supplied and bricated. The precursors themselves have very hi viscosities in the melt state and hence the flow characteristics tend to be very poor. Semicrystalline and amorphous polyamides (6) and aromatic sulfone polymers such as poly(phenylene sulfide), poly(ether sulfone) and polysulfone (7) have been blended with the precursor to PAI, to obtain better flow characteristics. 

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