Phosphorus-carbon polymers

Abstract Many similarities between the chemistry of carbon and phosphorus in low coordination numbers (i.e.,CN=l or 2) have been established. In particular, the parallel between the molecular chemistry of the P=C bond in phosphaalkenes and the C=C bond in olefins has attracted considerable attention. An emerging area in this field involves expanding the analogy between P=C and C=C bonds to polymer science. This review provides a background to this new area by describing the relevant synthetic methods for P=C bond formation and known phosphorus-carbon analogies in molecular chemistry. Recent advances in the addition polymerization of phosphaalkenes and the synthesis and properties of Tx-con-jugated poly(p-phenylenephosphaalkene)s will be described. 

Even though panially alkyl- and aryl-substituted polyphosphuzenes are accessible via the ring-opening polymerization followed by Ihe macro-molecular substitution rotile. polymers in which all suhsliiuems are allached through direct phosphorus - carbon bonds arc not yet accessible by Ibis method. 

The newest series of polymers based on a phosphorus-carbon backbone are poly(meth-ylenephosphines) of structure [-P(R)-CR2-] , produced by the polymerization of phospha-alkenes, P(R)=CR2.47a These polymers react with oxygen to form species of type [-P(R)(0)-CR2-] . A related polymer with phenyl rings in the backbone has also been described.47b This is a pi-conjugated polymer with P=C bonds in the main chain. 

An optimised solid-phase method for the generation of diverse a-amino-alkyl or -aryl phosphonates derived from peptides and polymer-assisted solution-phase parallel synthesis of dipeptide p-nitroanilides and dipeptide diphenyl phosphonates have been reported. A modular method for the construction of polypeptides containing the Phe-Arg phosphinic acid isostere has been described. A novel methodology for the solid-phase synthesis of phosphinic peptides has been developed in which the phosphorus-carbon bond was formed... 

Review papers on cyclic compounds with a phosphazene moiety have covered several areas, viz. metal complexes derived from organo-substituted, polymers with cyclotriphosphazene entities and chemistry of perfluorinated cyclo-phosphazenes. Azaphosphinines have been reviewed in the scope of the phosphorus-carbon heterocyclic chemistry. ... 

Thus far, the survey of phosphazene elastomers has been based on the formation and modification of poly(dlchlorophosphazene). Although a large variety of polymers can be prepared by this approach, there are limitations In the preparation of polyphosphazenes with phosphorus-carbon bonds. The reaction of poly(dlchlorophosphazene) with organometalllc agents, such as RMgX or KLl, results mainly In decomposition and not the desired polymers [NPR.]. There are three possible approaches to the preparation ox polyphosphazenes with phosphorus-carbon bonds polymerization of substituted trlmers, poly(dlfluorophosphazene), and thermolysis of small linear molecules. These three approaches will be discussed In turn. 

It has generally been assumed that the bonds that link the catalyst to the polymer support are chemically stable under the reaction conditions one employs. Until recently, the literature offered little information in this regard, since lifetime studies are needed to properly evaluate stability. Recent publications have pointed out the chemical instability of the phosphorus-carbon bond of tertiary phosphine functionalized supports and the chemical reactivity of various nitrogen functionalized polymeric support materials under reaction conditions. If such chemical stability problems are present, the consequences are indeed serious. While a typical "leach" situation would necessitate a periodic reloading of the metal complex, cleavage of polymer functionality would necessitate replacement of both the metal complex and the polymer. 

Phosphorus-containing polymers, especially those comprising vinylphosphonic acid (VPA) and vinylphosphonate moieties, have become attractive polymers on an industrial scale, due to their various applications based on the properties of the phosphonic group. In early applications, poly(VPA) and its derivatives were noted as efficient scale inhibitors in cooling and boiler water systems, by inhibiting the formation of calcium sulfate, carbonate, and phosphate and as flame retardants." ... 

PCA 16 is available as Beldene 161/164 (50/35% w/w solids), Acumer 4161 (50%), and Polysperse (50%). These are low-phosphorus content materials that have found application in boiler FW formulations because of excellent sludge conditioning and particulate dispersion properties. The number 16 represents a 16 1 w/w ratio of acrylic acid and sodium hypophosphite, giving PCA 16 a MW range of 3,300 to 3,900. PCA 16 is particularly effective for the control of calcium carbonate and sulfate deposition. It is usually incorporated with other polymers in formulations and is approved for use under U.S. CFR 21, 173.310. 

This review has shown that the analogy between P=C and C=C bonds can indeed be extended to polymer chemistry. Two of the most common uses for C=C bonds in polymer science have successfully been applied to P=C bonds. In particular, the addition polymerization of phosphaalkenes affords functional poly(methylenephosphine)s the first examples of macromolecules with alternating phosphorus and carbon atoms. The chemical functionality of the phosphine center may lead to applications in areas such as polymer-supported catalysis. In addition, the first n-conjugated phosphorus analogs of poly(p-phenylenevinylene) have been prepared. Comparison of the electronic properties of the polymers with molecular model compounds is consistent with some degree of n-conjugation in the polymer backbone. 

Palladium is known to be a metal that works catalytically in the system. Various supports can be used for Pd, such as active carbon, mesoporous materials, and polymers. All of them deactivate in the sitosterol hydrogenation, most probably because of sulfur and phosphorus impurities present in the raw material, which originates from the tall oil production, a side process of chemical pulping. 

Because of the processes carried out in the plant, the expected compounds in wastewater are formaldehyde, urea, and polymers of these compounds. The global effluent of this kind of factory is characterized by a high chemical oxygen demand (COD) (due mainly to formaldehyde), relatively high values of nitrogen (arising from urea and copolymers) and a low content of phosphorus and inorganic carbon. The main characteristics of the effluent of a resin factory are showed in Table 19.1. 

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