Gelation of Hydrophilic Polymer Bearing Metal-coordination Unit with Various Metal Ions

Abstract

Gelation of a hydrophilic polymer bearing a metal-coordination unit with various metal ions was examined. Gels with different morphologies were formed depending on the metal ion species. The formation mechanism for these gels could be explained based on their cross-linking rates. Gelation in two-component solutions containing different ratios of PdII to other metal ions (AuIII and PtIV) was also investigated.

Gelation of Hydrophilic Polymer Bearing Metal-coordination Units with Au(III) Ions: Application to Synthesis of Porous Gold

“…Dispersed aqueous solutions of HPMC with appropriate concentration (5,10,15,20,25, and 30 wt%, 0.3 mL, pH 1) were added to 4 mmol/L aqueous solutions of NaAuCl 4 (20 mL, pH 1) in test tubes, and the mixtures were allowed to stand at room temperature for 5 h. To determine the degree of cross-linking, the concentration of Au(III) ions (mmol) in the supernatant solution was measured by AAS. Calculation of the degree of cross-linking of Au(III) ions in the gels is described in the Results and Discussion.…”

“…3 Results and discussion 3.1 Gelation of hydrophilic polymer bearing metalcoordination unit with Au(III) ion HPMC was synthesized by the reaction of poly(vinyl alcohol) with methyl isothiocyanate according to our reported procedure. 27 To obtain the porous gels, dispersed aqueous solutions (0.3 mL, pH 1) of different concentrations of HPMC (5,10,15,20,25, and 30 wt%) were added dropwise to aqueous solutions of NaAuCl 4 (20 mL, pH 1) in a test tube, and the mixtures were allowed to stand at room temperature for 5 h. When the dispersed aqueous solution of HPMC with 5 wt% concentration was added to Au(III) aqueous solution, gelation did not occur and the HPMC solution fell to the bottom of the test tube (Fig. 1a).…”

“…[21][22][23][24] We previously reported self-assembled gelation of a hydrophilic polymer bearing a metal-coordination unit (HPMC) upon dropwise addition of a dispersed aqueous solution of HPMC to an aqueous solution of Au(III) ions. [25][26][27][28] HPMC contains thiocarbonyl groups for metal coordination and hydroxyl groups for hydrophilicity (Scheme 1). Gelation proceeds via cross-linking between the thiocarbonyl sulfurs and Au.…”