Characterization, Synthesis, and Application of Borate-selective Polymers

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Studies were done using commercially available linear dextran and crosslinked polyols such as Sephadex gel, QAE-Sephadex anion-exchange dextran gel, and Amberlite IRA-743, a boron-selective resin which has a functional group of N-methylglucamine. Together with the distribution measurements of borate on the crosslinked polymers, ^<11>B NMR spectroscopy was employed to elucidate the nature of the complex formation of borate with the polyols. The results obtained were as follows : (1) for the adsorption of borate on a crosslinked dextran. DELTAH values were comparable to those for the complex formation ob borate with monosaccharides and the borate concentration dependence of boron adsorption is a characteristic property of the crosslinked dextran. (2) Well-resolved ^<11>B NMR spectra for the solid gel as well as for a dextran solution were observed. In the dextran system, borate complexes both with alpha, beta-diols and alpha, gamma-diols of glucopyranoside residues were present. This cro … More sslinking of dextran caused the effective concentration of alpha, beta-diol moieties in the crosslinked polymer ligand to become higher than the practical concentrarion, so that the 1 : 2 complexation became more fovorable accoding to the increase in the degree of crosslinking. (3) The borate concentration dependence of boron adsorption on crosslinked dextran gel may be caused by the exclusion of borate anions from the gel phase due to electrostatic repulsion between borate and the fixed anion sites of borate complexes in the gel phase. The stability constant of each complex is similar to that for the Sephadex system : the presence of the fixed cation group in the QAE-Sephadex gel phase did not promote the boron adsorption. (4) The pH of the N-methylglucamine resin phase remains constant in the range of 10 to 11 when the equilibrated bulk solution is pH 6-11. The strong adsorbability of borate on the resin in a wide pH range is due to this phenomenon. From the ^<11>B MAS-NMR measurements, the active species in the resin were proved to be borate complexes of alpha, beta-diols in the functional groups.On the basis of the results obtained, a novel boron-selective polymer was synthesized by introducing tris (hydroxymethyl) groups into chloromethylated polystirene. The properties of this resin are now being investigated. Less