- 作者: 陳志鴻 ; 黃良平
- 作者服務機構: Dept. of Chemistry, National Chunghsin Univ., R.O.C.
- 中文摘要: An aqueous PVA-Cu/sup 2+/ solution at pH = 3 is in the hydrated form and becomes green at pH .gtoreq. 6 with a decrease in viscosity. The structure of the copper ion is suggested to be that of a polynuclear complex at pH > 6. For the green solution the polynuclear chains of the copper complex are believed to be surrounded by the PVA chains with the hydrophobic backbones facing toward the inside and the hydrophilic OH groups oriented toward the outside facing the bulk water. The proton spin- lattice relaxation rate 1/(T/sub 1p/)and the spin-spin relaxation rate 1/T/sub 2/ of CH and CH/ sub 2/in PVA and H/sub 2/O for aqueous PVA-Cu/sup 2+/solutions at pH=3, can be explained by the two site exchange model in the region of the fast exchange limit. The dipolar correlation time .tau./sub c/ is dominated by the reorientational process with a dipolar correlation time of 2.11x10/sup -11/s. When the pH rises from pH=3 to pH=12.5, the variation of 1/(T/sub 1P/)and 1/(T/sub 2P/)of CH and CH/ sub 2/ in PVA with Cu/sup 2+/ ion concentration in aqueous PVA-Cu/sup 2+/ solution at pH=12.5 can be explaind in terms of the relaxation by an inclusive model of the polynuclear copper complex and PVA. Furthermore, the frequency (or field) dependence of 1/(T/sub 1P/),1/(T/sub 2P/) of CH in PVA for aqueous PVA-Cu/sup 2+/ solution at pH=12.5 suggests that the dipolar relaxation is dominated by the electron-spin relaxation with the electron spin relaxation time T/sub 1e/=1-2 x10/sup -10/s. The invariance of 1/(T/sub 1P/) and 1/(T/sub 2P/) of H/sub 2/O with the variation of the Cu/sup 2+/ ion concentration in aqueous PVA-Cu/sup 2+/solution at pH=12.5 supports the hypothesis that the water is not directly bound to the Cu/sup 2+/ ion.
- 英文摘要: --
- 中文關鍵字: Pva; Cu/Sup 2+/; Proton Relaxation
- 英文關鍵字: PVA;二價銅離子;質子鬆弛