Sulfonated PPO

The first step involved the reaction of PPO with chlorosulfonic acid according to a literature method (H). The sulfonated PPO was hygroscopic and unstable. We succeeded (12) in converting the sulfonate groups into stable sulfone groups by reacting them with aromatic compounds at elevated temperatures (120 0. The final dark solution was washed with dilute sodium bicarbonate, and the product precipitated in methanol, filtered and dried. 

Styrenic-siloxane block and graft copolymers, Tg dependence on architecture and molecular weight, 95,95/ Styrenic-siloxane block copolymers, 86 Substrate catalyst ratio, chloromethylation, 18 Sulfonation, instability of sulfonated PPO, improvement, 6 Surface grafting... 

Poly N-amideimide (UOP) Polybenzooxadinon (Bayer) Polyhidantoin (Bayer) Sulfonated polysulfone Sulfonated PPO (GE) NS-100 (North Star) ... 

Blends of PPO with PS containing sulfonated and carboxylated groups have been reported in various studies [394-396]. The miscibility of sulfonated PS with PPO, sulfonated PPO with PS and blends of the sulfonated polymers was reported by Hseih and Peilfer [394]. Miscibility was maintained with sulfonation levels up to 2-4mol% for PS with sulfonated PPO and sulfonated PS with PPO. When both polymers were sulfonated, phase separation occurred at higher levels (> 10mol% sulfonation). The miscibility can be influenced by counter ion, as noted in a comparison of a Zn + neutralized sulfonic acid modified PS, which exhibited a larger miscibility window with PPO than the Na neutralized coimterpart [396]. Syndiotactic polystyrene was noted to be miscible over the entire composition range in amorphous blends with PPO, where the Tg versus composition followed the Fox equation predictions [397]. Isotactic polystyrene miscibility with PPO has also been observed, with crystallization and orientation data reported on the blend [398]. 

Blends of sulfonated PS and sulfonated PPO have been described in several papers as offering a combination of high proton conductivity and low methanol permeability [104, 105]. Optimum conductivity was obtained with a 50/50 blend of the sulfonated polymers, with each having an identical ion exchange capacity [104]. The miscibility of the PS/PPO system appeared to be maintained with the blend of the sulfonated polymers. Polybenzimidazole (PBI) and polysulfone (PSF) are immiscible however, sulfonated PSF is miscible with PBI and showed utility in phosphoric acid based fuel cells operated upto200°C[106]. PEMs comprised of Nafion and a vinylidene fluoride-hexafluoropropylene copolymer blend were evaluated... 

As an aromatic polymer, PPO can be sulfonated using concentrated sulfuric acid, chlorosulfonic acid, pure or complex sulfur trioxide, or acetyl sulfate [413—419]. The sulfonation can be easily controlled by adjusting time, temperature, concentration, and solvents. Sulfonated PPO (sPPO) has been considered as a good proton... 

Klebe reported that the chlorosulfonation reaction on P3O was best carried out in nitromethane solvent. Sulfonation under these conditions takes place exclusively on the backbone of the polymer. When carried out in chloroform solution cross-linking reactions took place. This polymer was utilized by Hodgdbn to make a fuel cell membrane. Sulfonated PPO and P3O undergo slow desulfonation reactions at 100°C in the presence of water. In order to force the sulfonation reaction to take place on the pendent phenyl groups, and hence give a more hydrolytically stable polymer, the polymer was first brominated on the backbone followed by sulfonation. ... 

Bikson has carried out an extensive study on the preparation of sulfonated PPO. He described the purification of PPO and also found that it was advantageous to utilize the lithium salt in preparation of membranes. Cabasso has utilized this technology to prepare blends of PPO with poly (vinylidene fluoride)... 

As a result of greater hydrophilicity, the solubility characteristic of sulfonated PPO is completely different from this of PPO. Table 3 describes the solubility of LMW HSPPO-37.3 compared to the unmodified polymer. It can be noticed that HSPPO-37.3 becomes soluble in dipolar aprotic solvents such as DMSO, DMF, and DMAC in which PPO is insoluble. The change in solubility characteristic of HSPPO compared to PPO is very important since dipolar aprotic solvents are commonly used for preparation of polymeric membranes. 

Sulfonated PPO in protonated form is an unstable material, which decomposes liberating sulfuric acid. Degradation of HSPPO is enhanced at elevated temperatures. For example, annealing HSPPO for 24 h at 120 C and 140 C results in a decrease of the DS from 18.5 to 11.2 and 7.8%, respectively [17]. On the other hand, at room temperature and moisture free environment, for example in vacuum or in presence of a dry gas, the stability of HSPPO is significantly improved. 

Fu H, Jia L, Xu J. Studies on the sulfonation of polyphenylene oxide (PPO) and permeation behavior of gases and water vapor through sulfonated PPO membranes. I. Sulfonation of PPO and characterization of the products. J. Appl. Polym. Sci., 1994 51 1399-404. 

The general procedure for the sulfonation of PPOBr was similar to that described by Plummer et al. for the sulfonation of low molecular weight PPO. However, slight changes had to be made in order to adjust to the increased viscosity of the solution in chloroform. A 2 wt. % solution was reacted with stoichiometric amount of chlorosulfonic acid instead of 10 wt. % solution as was used for sulfonating PPO of low molecular weight. The... 

The permeability and permeability ratio of dense films made from SPPOBr of varied degrees of sulfonation and bromination are shown in Table 12. Performances of carboxylated PPO (CPPO) and sulfonated PPO (SPPO) dense films are also presented for comparison. 

SPPO was first prepared by sulfonating PPO of intrinsic viscosity of 1.58 dL/g in chloroform at 2S C. Solutions of SPPOH in different solvents like ethoxyether and butoxyether were coated onto the surface of commercial polyethersulfone ultrafiltration membranes. All coated membranes were dried at 60° C for overnight. TFC membranes prepared from a solution of SPPO in ethoxyethanol demonstrated higher permeances and permeance ratios for CO2/CH4 gas pair. These membranes were immersed in solutions of alkali metal hydroxide or alkaline earth metal hydroxide of 0.1 to IN concentrations, depending on the solubility of the respective hydroxide in water. When the solubility was low, the solution saturated with hydroxide was used. The TFC membranes were kept immersed for 48 hours at room temperature to complete the exchange of the proton with metal cations. Solutions of magnesium nitrate and aluminium chloride were used to replace the proton with Mg and AF respectively. 

A comparison was made between sulfonated PPO (5 microns thickness, lEC 2.4 cast from 2/1 chloroform/methanol mixture), ultra-thin membrane of cellulose methylsulfonate o-propyl sulfonic acid and asymmetric cellulose acetate membrane in the treatment of alkaline copper cyanide feed. The reverse osmosis experiments were conducted in the following five steps. 

Table 2. Performance of sulfonated PPO membranes with secondary sewage ...

PPO and PPOBr were sulfonated by reacting with chlorosulfonic acid in chloroform [49]. The degree of sulfonation was determined by acid-base titration method. Under the reaction conditions only mono-aryl substitution of PPO and PPOBr occurred. The polymers were converted to the salt form by replacing the proton of the sulfonic acid group with Na-cation. Sulfonated PPO (SPPO) and sulfonated brominated PPO (SPPOBr), both in the Na-cation form (SPPONa and NaSPPOBr), were used for water removal studies. 

Jia L., Fu H., and Xu J., Studies on the Sulfonation of Poly (phenylene oxide) (PPO) and Permeation Behavior of Gases and Water Vapor Through Sulfonated PPO Membranes. III. Sorption Behavior of Water Vapor in PPO and Sulfonated PPO Membranes, J. Appl. Polym. Sci., 1994, 51, 1399-1404. 

---