Synthesis of Higher Molecular Weight Poly(D-glucaramides) and Poly(aldaramides) as Novel Gel Forming Agents

Poly(alkylene D-glucaramides) with higher molecular weights than previously reported were prepared through a multi-step process beginning with 1:1 alkylenediammonium D-glucarate salts. These salts set a precise stoichiometric equivalence between co-monomers, a necessary requirement for higher molecular weight condensation polymers. The salts were prepared by treating monopotassium D-glucarate with H+ form ion exchange resin to give D-glucaric acid, which was then reacted with a diamine. The glucarate portion of the salt was activated for polymerization through esterification in HCl/methanol. Polymerization was initiated by basification of the resulting mixture. The molecular weights of the polymers showed strong dependence on the base used in the basification step. Sodium methoxide was found superior to triethylamine for efficient deprotonation of the diammonium salt to yield higher molecular weight polyamides. The molecular weights of the resulting polymers were further increased through a second polymerization reaction in a dimethylsulfoxide and ethylene glycol solvent mixture which provides greater solubility for the polymers. The resulting poly(D-glucaramides) were found to serve as novel gel forming agents in aqueous solutions. Poly(hexamethylene D-glucaramide) formed rigid gels upon addition of water to a dimethylsulfoxide solution of the polyamide. By tailoring the water solubility profile of poly(alkylene D-glucaramides) through the use of two different diamines in the polymerization process, hydrogels were formed without dimethylsulfoxide and at low polymer concentrations (0.3-0.5%). The gelation of poly(aldaramides) is influenced by the aldaryl unit as polyamides from xylaric acid and galactaric acid have inferior gel forming ability compared to those from D-glucaric acid. The nitric acid oxidation of D-glucose to D-glucaric acid was also investigated with emphasis on isolation and purification of the organic acid oxidation products. Oxidation reactions were carried out in an automated reactor using three and four equivalents of nitric acid to D-glucose. Removal of residual nitric acid from the organic acid products was accomplished through vacuum distillation of the reaction mixture followed by filtration through either a diffusion dialysis unit or a nanofiltration system. While nanofiltration showed higher selectivity for separating nitrate, diffusion dialysis was capable of operating at higher feedstock concentration and at low pH