Polycondensations phosphonic acid

The addition of finely dispersed solid particles improves the IR absorption of the polymer and positively influences blowing of the preforms. Such solid particles can be obtained by the reduction of Sb3+ to metallic antimony during polycondensation by the addition of trivalent phosphorous compounds such as phosphonic acid or its esters (phosphites). However, only a slight improvement in properties could be achieved by this approach [35],... 

When the disodium salt of l,2-bis(methoxycarbonyl)ethane phosphonic acid is applied, poly(ethylene terephthalate) with the structure given below was obtained [93,94]. It was found that the polycondensation stage proceeds normally at 1-9% (by weight) of the... 

Aromatic polymers with phosphonated sites directly linked to the main chain have also been prepared by direct polymerization (Scheme 13.2a-d). For example, phosphonated poly(l,3,4-oxadiazole)s have been prepared by direct polycondensation of l,4-dicarbo3y-2-phenyl-phosphonic acid and their dihydrazides in an ionic liquid using triphenyl phosphite as a reaction activator. " The membranes obtained from these polymers were thermally and chemically stable and possessed proton conductivities in the range between 4x10 " and 5x10 mS cm at 100% RH, which is three orders of magnitude lower than the state-of-the-art PFSA membrane Nation . 

Recently, Baneqee et al. developed an easy synthesis strategy of phos-phonic acid-containing diphosphonated poly(ether ether ketone) (PEEK) by polycondensation of difluorobenzophenone and phosphonated bisphenol A, characterized the structures using NMR, Fourier transform infrared (FTIR) spectroscopy, and electrospray ionization mass spectrometry, and estimated that the degree of phosphonation is about 70% from proton NMR spectra [17]. Jiang et al. studied the proton conductivities of poly(vinylbenzyl phosphonic acid) homopolymer and its statistical... 

In addition, there are several investigations on proton exchange polymers, whose phosphonic acid sites are linked to aromatic ring directly or by means of alkylene spacers. These polymers can be prepared by polycondensation of phosphonic acid functionalized monomers or phosphorylation of existing aromatic condensation polymers. There are several methods reported for the preparation of arene phosphonates from aryl bromides [38-40]. The classical Arbuzow reaction [41,42] is commoifly used, in which triethylphos-phite and nickel dichloride are employed as catalysts. The reaction often requires harsh conditions (160 °C) and suffers from low yields. Alternative paUadiiun-catalyzed reaction [43-45] useful for phosphonation proceeds more smoothly. 

In general, few articles on the polycondensation of phosphonic acid functionalized monomers can be found. 

Polycondensation reactions of 2-chloroalkyl phosphates or phosphonates to obtain products having a controllable degree of condensation and low acid or latent acid contents were accomplished in our laboratory using catalysts such as quaternary ammonium salts, amines, amides, sodium carbonate, or lithium chloride (5). Reduction of the temperature diminished the... 

In melt polycondensation the phosphonic or phosphoric dichloride is mixed with the diol in the absence of solvent. A Lewis acid catalyst, such as FeCls or MgCl2 is added and the mixture is heated, in vacuo or in nitrogen blanket, in order to remove the hydrochloric acid that is formed. 

Several synthetic strategies have been developed to prepare phosphonated aromatic polymers, where the acid groups are attached either directly " or via spacers to an aromatic backbone. " These polymers can be prepared either by post-phosphonation of prepolymers via, e.g. transition metal catalyzed Michaelis-Arbuzov reactions and lithiation chemistiy, or by direct polymerization of phosphonated monomers via polycondensation. Both synthetic strategies then require hydrolysis of the esters to obtain the free acid. The former strategy requires the formation of C-P bonds in the polymer structure, and the latter necessitates the synthesis and purification of suitable monomers. 

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