PHOSPHORUS-CONTAINING POLYMER

Polymers with a variety of chemical, physical, and biological properties can be produced by varying the side groups attached to the phosphorus in the polymer backbone. Different polymers are usually produced by performing substitution reactions on the base polymer, poly(dichlorophosphazene), for example  

This basic structure provides for considerable flexibility in the design of biomaterials, as described in a recent review [27]. By selection of the side groups on the polymer chain, both hydrophobic and hydrophilic polymers can be produced. Hydrophobic polyphosphazenes may be useful as the basis of implantable biomaterials, such as heart valves. The hydrophilic polymers can be used to produce materials with a hydrophilic surface or, when the polymer is so hydrophilic that it dissolves in water, cross-linked to produce hydrogels or solid implants. In addition, a variety of bioactive compounds can be linked to polyphosphazene molecules allowing the creation of bioactive water-soluble macromolecules or polymer surfaces with biological activity. 

Polymerization of cyclic monomers containing P-atoms in the ring has been recently reviewed by Penczek and Lapienis elsewhere 1 K The intensively studied cyclic phospha-zenes (PZ) were recently reviewed several times, mostly by Allcock 2,3,4). In this chapter we discuss only the main features of the cationic polymerization of these compounds. 

The following groups of P-containing compounds were cationically polymerized 2-substituted-2-oxo-l,3,2-dioxophospholanes (ODPL) and the corresponding phos-phorinanes (ODPR), 2-substituted-l,3,2-dioxaphospholanes (DPL) and phosphori-nanes (DPR), 2-substituted-l,3,2-oxazaphospholidines (OAP) and 2-substituted-1,2-oxaphospholanes (OPL)  

No information is available on the cationic polymerization of cyclic phosphines.  

The cationic polymerization of the above listed monomers usually leads to low-and medium-molecular-weight products (Mn 104). In contrast to cationic processes anionic polymerizations lead to higher-molecular-weight polymers (Mn m 105)5). 

Although no other phosphorus-containing polymers synthesized cationically have been commercialized, they exhibit interesting properties due to their composition, i.e., low flamability, flame retardancy and high efficiency to complex heavy metal ions. 

Many phosphazenes are known to depolymerize on heating but the evidence suggests that polybis(p-isopropylphenoxy)phosphazene is degraded by a random chain scission. This was attributed to the existence of cyclic transition states at the branch site locations.  

Capon and S. P. McManus, Neighbouring Group Participation, Plenum, New York, 1974. 

The acylation of the cyclohepta-amylose anion in 60% DMSO 40% water by the 4-nitrophenyl ester of ferrocinnamic acid (1) is accelerated over 50 000-foId compared with the hydrolysis by buffer alone. The actual rate achieved is similar to that for the acylation of -chymotrypsin by 4-nitrophenyl acetate. This is the greatest acceleration observed for cycloamylose catalysis, but at the same time highlights one of the difficulties of using this class of compounds as general catalysts. The optimum substrate structure has to be found for the catalyst. According to molecular models, (1) fits snugly into the preformed cavity. 

There are few examples of cydoamylose- catalysed reactions which are of synthetic utility. However, cyclohepta-amylose catalyses a variety of specific alkylation-oxidation reactions, e.g., the production of (3) and (4) from (2), and it has been postulated that inhibition of oxidative fragmentation of the C(2)—C(3) bond of the quinone is due to its location deep in the cydoamylose cavity.  

Cydoamyloses have been functionalized. For example, attached phosphoric acid groups catalyse the enolization of ketones and some catalyse the hydrolysis of acetals. Attached imidazole groups have been used as models for ribo-nuclease. Cydoamyloses functionalized with polyamines interact strongly with metal-ions and the resultant complex binds hydrophobic anions more strongly than the cydoamylose without metal-ion co-ordination.  

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Phosphorus-Containing Polymers. A large number of addition and condensation polymers having phosphoms built in have been described, but few have been commercialized (131,132). No general statement seems warranted regarding the efficacy of built-in vs additive phosphoms (133). However, in textile fibers, there is greater assurance of permanency. 

Of the phosphorus-containing polymers the polyphosphates have been known for many years. Aluminium phosphate had been used in the manufacture of heat-resistant silica-fibre-reinforced laminates. 

It has been observed that all the phenoxaphosphine ring-containing polymers have excellent thermal stability and show better heat resistance than open-chain phosphorus containing polymers. The phenoxaphosphine polymers containing aromatic rings in the backbone show little degradation below 400°C in air. 

Our interest in such compounds stems mainly from the possibility that they might be useful precursors to new classes of phosphorus-containing polymers or cyclic oligomers. Functional linkages such as E = NSiMe3 or CR SiMe3 could serve as sites for condensation-polymerization reactions, leading to novel cyclic or polymeric sys terns, ... 

Chaubal MV, Gupta AS, Lopina ST, Bruley DF. Polyphosphates and other phosphorus-containing polymers for drug delivery applications. Crit Rev Ther Drug Carrier Syst 2003 20(4) 295-315. 

Like other elements important in inorganic chemistry, phosphorus is used mainly in combination with other elements in a polymeric chain 43,44 Small amounts of phosphorus in a polymer can be greatly advantageous, imparting flame retardancy, improved adhesion to metals, and ion-binding characteristics. Phosphorus-containing polymers are therefore extensively used as flame retardants for fabrics, as adhesives, and as ion-exchange resins. 

In order to limit extensive side reactions (advanced destruction of the support-polymer, modification of grafting monomers structure) which usually accompany grafting reactions in electrical discharge conditions, we have elaborated the solid-solid grafting procedure in cold plasma. Thus, the rayon fabric was grafted with halogen and phosphorus containing polymers in... 

In this paper, the surface grafting of rayon fabrics with nitrogen and phosphorus containing polymers in cold plasma is studied. The analytical data (IR spectroscopy, TGA, electron microscopy, elemental analysis, etc.) indicate the formation of grafted copolymers. The grafted rayon fabrics present improved flame-retardant properties, the best behavior was proved by those grafted with polyurea of phosphinic acid. 

Our investigations suggest that grafted copolymers are obtained probably by the recombination reactions of the macroradicals generated both on the cellulosic support and on the nitrogen and phosphorus containing polymers. 

It can be presumed that under cold plasma conditions, the nitrogen and phosphorus containing polymers can lead also to the macroradicals through dehydrogenation of CH aromatic and aliphatic or NH groups. 

Simionescu, C.I., Denes, F., Macoveanu, M.M., Cazacu, G., Totolin, M., Percec, S., and Balaur, D. 1980. Grafting of rayon fabrics with phosphorus containing polymers in cold plasma in order to obtain flame-retardant materials. Cell. Chem. Technol., 14 869-883. 

The concept of no catalyst copolymerization has demonstrated its usefulness in the exploration of phosphorus-containing polymers. For example, the cyclic phosphonite 34 was successfully copolymerized both with p-propiolactone (31) and acrylic acid 35). These copolymerizations proceed via a common zwitterion 36 and hence produce the same copolymer 37. 

Phosphorus-containing polymers, which can exhibit biological activity, have aroused considerable interest. Other such polymers are excellent fire retardants. 

Table 7 Common phosphorus-containing polymers—polyphosphazenes Polyphosphazene linkage...

Table 8 Common phosphorus-containing polymers—polyphosphoesters...

Sander, M. and Allcock, H.R., "Phosphorus-Containing Polymers," articles in Encyclopedia of Polymer Science and Technology, Vol. 10, pp. 123-144, edited by N.B. Bikales, Wiley-Interscience, (1969). 

Morgan, A.B. Tour, J.M. Synthesis and testing of nonhalogenated alkyne/phosphorus-containing polymer additives potent condensed-phase flame retardants. J. Appl. Polym. Sci. 1999, 73, 707-718. 

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