Sulfonated phenol-formaldehyde polymer

BF3.OH2).217 The use of a sulfonated phenol-formaldehyde polymer in conjunction with formic acid is also reported.208 Acids that are ineffective include phosphoric,208 trichloroacetic, dichloroacetic, and acetic acids.134 It is reported that addition of lithium perchlorate to the reaction mixture improves product... 

Sulfonated phenol-formaldehyde polymer is the first hydrocarbon-based polymer membrane in the literature. The phenolic polymer membrane was prepared by condensation polymerization of sulfonated phenol with formaldehyde, but the sulfonated phenolic polymer had low chemical and mechanical stability for fuel cell applications. 

In general, the acid-sorbing resins may be classified as high molecular weight polyamines or polyimines. Thus, the original Adams and Holmes material was a polymer of m-phenylenediamine. Cation Exchange materials include synthetic resins, such as sulfonated phenol-formaldehyde or polystyrene types, and sulfonated coal. Some manufacturers have a variety of sub-types which are considered superior for particular applications. 

The first example in this class of PEMs to be examined was sulfonated phenol-formaldehyde resins (8).i These materials were studied for use in the space program, given the relative ease of the synthesis and sulfonation of the base polymer as well as low cost. However, in common with polystyrene, these systems exhibit low oxidative stability and thus little work has been carried out since the original studies. 

Initially, poly(styrenesulfonic acid) (PSSA) and sulfonated phenol-formaldehyde membranes were used for PEFCs, but the useful life of these materials was limited because of significant degradation under fuel-cell operating conditions. A critical breakthrough was achieved with the introduction of Nafion , a perfluorinated polymer with side chains... 

As just mentioned, strong or weak acidic ion exchangers contain sulfonic acid or carboxylic acid groups in the H or alkali metal salt form and consist of 1,4-divinylbenzene cross-linked polyst3Tene or poly(acrylic acid) as shown in formulae 7a and 7b. Another example is the sulfonated phenol-formaldehyde condensation polymer 8. The preparation of ion-exchange resins and the determination of their capacities are described in Section 5.4, Experiments 5-1 and 5-2. 

When two polymeric systems are mixed together in a solvent and are spin-coated onto a substrate, phase separation sometimes occurs, as described for the application of poly (2-methyl-1-pentene sulfone) as a dissolution inhibitor for a Novolak resin (4). There are two ways to improve the compatibility of polymer mixtures in addition to using a proper solvent modification of one or both components. The miscibility of poly(olefin sulfones) with Novolak resins is reported to be marginal. To improve miscibility, Fahrenholtz and Kwei prepared several alkyl-substituted phenol-formaldehyde Novolak resins (including 2-n-propylphenol, 2-r-butylphenol, 2-sec-butylphenol, and 2-phenylphenol). They discussed the compatibility in terms of increased specific interactions such as formation of hydrogen bonds between unlike polymers and decreased specific interactions by a bulky substituent, and also in terms of "polarity matches" (18). In these studies, 2-ethoxyethyl acetate was used as a solvent (4,18). Formation of charge transfer complexes between the Novolak resins and the poly (olefin sulfones) is also reported (6). 

The phenol-formaldehyde prepolymers were polymerized with 4-(l-phenylethyl)phenol (para-styrenated phenol) (equation 39). The sulfonation of the resulting polymer gave a cation exchange resin, which is useful as an acid catalyst . ... 

Preparation of Cation Exchanger 8 by Sulfonation of a Phenol-Formaldehyde Condensation Polymer (Section 5.1.1)... 

Sulfonation of the phenol-formaldehyde condensation polymer 40 g of the uncross-linked phenol-formaldehyde condensation polymer are gradually wanned to 140 °C in 120 g of 95% sulfuric acid in a 250 mL round-bottomed flask fitted with a reflux condenser. As soon as the resin has completely dissolved, the solution is cooled to room temperature, poured into an iron dish and 30 mL of 37% aqueous formaldehyde solution are stirred in with a spatula as quickly as possible. The metal dish is then placed in an oil bath at 110 °C and the resin allowed to harden for 2 h. The cooled product is washed with water, broken up with a hammer, and ground down to pieces of 1-3 mm size in a mortar. The particles are then washed with water until the washings are clear. 

Figure 13 Attenuation plots for a variety of polymer systems as a function of temperature (a) poly(phenylene sulfide) (b) poly(ether sulfone) (c) polyester DMC (d) copoly(acrylonitrile/styrene/acrylate) (e) poly(acrylonitrile/butadiene/styrene) (f) polystyrene (toughened) (g) polyester resin (h) melamine formaldehyde (i) polyimide (j) ekonol (k) nylon 6 (1) poly-(phenylene oxide) (m) polypropylene (n) phenol formaldehyde (o) poly(vinyl chloride) (rigid) (p) poly(vinyl chloride)...

The industrial chemist will find several references to the direct sulfonation of polymers to produce ion exchange resins and water-soluble materials. For example, chlorosulfonic acid is used to treat polystyrene to give an ion exchange resin. In addition phenol formaldehyde resins can also be sulfonated. 

Acid catalysts, such as metal oxides and sulfonic acids, generally catalyze condensation polymerizations. However, some condensation polymers form under alkaline conditions. For example, the reaction of formaldehyde with phenol under alkaline conditions produces methy-lolphenols, which further condense to a thermosetting polymer. 

Membranes which may be used in the removal of alkali metal ions by electrodialysis are those which are impermeable to anions, but which allow the flow therethrough of cations. Such cation-selective membranes should, of course, possess chemical durability, high resistance to oxidation and low electrical resistance in addition to their ion-exchange properties. Homogeneous-type polymeric membranes are preferred, for example, network polymers such as phenol, phenosulfonic acid, formaldehyde condensation polymers and linear polymers such as sulfonated fluoropolymers and copolymers of styrene, vinyl pyridine and divinylbenzene. Such membranes are well known in the art and their selection for use in the method of the invention is well within the skill of the art. 

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