Vinyl monomers phosphonic acid

Figure 17-8. Monomers for synthetic thickeners vinyl phosphonic acid, N-vinyl-2-pyrrolidone, vinyl sulfonic acid.

Ester hydrolysis is most conveniently used because (1) its reaction mechanism is well established, and (2) both substrate and transition state analogs are easy to obtain. In Fig. 8.8b, phosphonic acid (2) is used as a transition state analog of the hydrolysis of substrate 3 [26]. A vinyl monomer of amidine 1 is chosen as a functional monomer because it readily forms stable complexes with the carboxylic acid ester and the phosphonic acid monoester. The imprinted polymers are synthesized in THF from 1 (the monomer), 2 (the template), and ethylene glycol dimethacrylate (the cross-linker) by using AIBN as the radical initiator. 

Various phosphonated block and graft copolymers have been prepared in order to obtain membranes with high local concentrations of phosphonic acid. The block copolymers have mainly been based on phosphonated and non-phosphonated vinyl monomers, whereas the graft copolymers have been based on polymers with aromatic backbones such as PAESs, poly(phenylene oxide) (PPO), and PBI, from which phosphonated vinyl monomers have been grafted. 

Phosphonates. The principal synthetic routes include addition and condensation methods. Although a large number of vinyl and diene phosphonate monomers have been described in the literature (2,5,7,62), only bis(2-chloroethyl) vinylphosphonate (Akzo-Nobel s Fyrol Bis-Beta monomer), vinylphosphonic acid (Clariant), and dimethyl vinylphosphonate (Clariant) have been offered commercially. The diethyl vinylphosphonate is available in laboratory quantities. 

There seems to be a number of other candidates suitable as a third comonomer (e.g., trilluorovinyl monomers containing phosphonic acid, sulfonamide, sulfraiimide, and/or cross-linkable moieties) [8-12], however, high production cost of these rather complex perfluorinated vinyl compounds may be an obstacle to the practical industrial applications. 

To furnish a convenient reaction platform, polymer chemists have explored the utility of non-isocyanide-based MCRs in order to avoid the use of isocyanides. For example, Tao and coworkers focused intensively on the employment of non-isocyanide MCRs such as the BigineUi reaction [70] and the three-compmient reaction between aldehydes, amines, and mercaptoacetic acid [71]. In additimi, the utility of the Kabachnik-Fields reaction was demonstrated independently by the groups of Theato [72] and Tao [73]. To be precise, Kakuchi and Theato showed that the Kabachnik-Fields post-polymerization modification reaction on poly(4-vinyl benzaldehyde) with amines and phosphites proceeded very efficiently to afford polymers featuring a-amino phosphonate pendant groups (Scheme 3) [72]. Furthermore, the group of Tao succeeded in synthesizing polymeric a-amino phosphonates via concurrent Kabachnik-Fields reactions of vinyl compounds and RAFT polymerization of the vinyl monomers in a one-pot process [73]. 

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