Complexation of borate with poly(1-(acrylamido)-1-deoxylactitol):: Dilute solution viscosity, 11B NMR, and 13C NMR studies

The interaction of borate ions with poly(1-(acrylamido)-1-deoxylactitol) (PACL) in aqueous media was investigated. Dilute solution viscometry revealed that low concentrations of Borax (Na2B4O7) increased the. intrinsic viscosity of PACL, while higher concentrations reduced it. B-11 NMR spectra of borate complexes of methyl beta-D-galactopyranoside (M(beta)DGP) (taken to model the C-l' through C-6' portion of the PACL repeating unit) and the monomer 1-(aclylamido)-1-deoxylactitol (2) showed evidence for alpha,beta-bidentate, alpha,beta-dimer, and alpha,gamma-bidentate borate complexes. The B-11 NMR spectrum of PACL-borate showed alpha,beta-bidentate and alpha,beta-dimer only. The binding constants for the alpha,beta-bidentate and alpha,beta-dimer complexes were determined for M(beta)DGP and 2 by integration of the B-11 NMR signals. C-13 NMR was used to identify the putative sites of complexation on PACL by comparing the spectra of borate complexes of M(beta)DGP and 2 with PACL-borate. Complexation was found to occur predominantly at the C-6', C-4', and C-3' positions.