Polyphosphoric acid characteristics

A simple example of gel formation is provided by chitosan tripolyphosphate and chitosan polyphosphate gel beads the pH-responsive swelling abihty, drug-release characteristics, and morphology of the gel bead depend on polyelectrolyte complexation mechanism and the molecular weight. The chitosan beads gelled in pentasodium tripolyphosphate or polyphosphoric acid solution by ionotropic cross-hnking or interpolymer complexation, respectively. 

With their extensively delocalized-electron systems along their backbones, PBX polymers have emerged as ideal candidates for NLO applications. We are particularly interested in their third-ordered susceptibility characteristics. Indeed, it has been shown " that PBZT film processed from polyphosphoric acid (PPA) solution had a relatively high value of about 3 x 10"" e.s.u. Further improvement in the optical quality of the PBZT film by coagulation of a methanesulfonic acid (MSA) solution in water had increased the x (3) value by an order of magnitude (3.3-4.5 x 10 e.s.u.). Since the three-fused-ring... 

The principal phosphation reagents used to manufacture phosphate esters are phosphoric anhydride (P4O10), phosphorus oxychloride [P(0)Cl3], and polyphosphoric acid. It is important to understand the physical and chemical characteristics of each raw material. The structure of the phosphation agent affects its reactivity and selectivity, resulting in variation in the monoester, diester, and triester product distribution. 

Accordingly, for the molar fractions x(P205),x(H20),x (H3P04), and i (H20) and for wt% H3PO4 in Table 12.2, the formation of polyphosphoric acids is not taken into account An overview is given for the most commonly used and characteristic composition of aqueous phosphoric acid. 

Apparently, the cyclization of 5-phenyl-3-oxobutanethioates (181) to 2H-1-benzothiopyran-2-ones (182) in polyphosphoric acid is successful only with the m-methoxy-derivative (181 R = m-MeO). In all other cases the isomeric thiochromones, e.g. (183), are formed. Spectroscopic methods of distinguishing between these hitherto difficultly distinguishable isomers are discussed. In the H n.m.r. spectrum the thiochromones show characteristic deshielding of the 5-proton by the peri carbonyl group. Equally diagnostic are their mass spectra, which show fragmentation of the parent ions to the ketens (184) by a retro-Diels-Alder reaction. 

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