《高分子物理》chapter4.ppt

Chapt 4 Molecular Weight and Molecular Weight Distribution of Polymers Molecular weight and molecular weight distribution MW Distribution 4.2 Measurement of Molecular Weight Vapor-phase osmometry (VPO, 气相渗透法) Membrane osmometry (膜渗透压法) Membrane osmometry (膜渗透压法) Static light scattering (静态光散射) Theory of Light Scattering (1) small particles dl/20 (Rayleigh ratio)瑞利比 (2) large particles dl/20 The Zimm-Plot Small angle laser light scattering Solution viscosity as a measure of polymer molecular weight Nomenclature (术语) of solution viscosity Viscosity measurement Treatment of viscosity data 4.3 Measurement of MWD Molecular Weight Fractionations (分子量分级) of Polymers Gel permeation chromatography (凝胶渗透色谱) 凝胶色谱标准曲线 MW and MWD Universal calibration (普适标定) * * 4.1 高聚物分子量和分子量分布的表示方法 4.2 分子量的测定方法 4.3 分子量分布的测定方法 4.2.1 数均分子量的测定方法 4.2.2 重均分子量的测定方法 4.2.3 粘均分子量的测定方法 Distribution of molecular weights in a typical polymer 4.1 Definitions of Average MWs and MW Distribution n: total mole number; ni: mole number of ith molecule with mole mass of Mi; Ni: mole fraction of ith molecule; w: total weight of the sample; wi: weight of the ith molecule; Wi: weight fraction of ith molecule. (1) Number-average molecular weight (数均分子量): (2) Weight-average molecular weight (重均分子量): (3) Z-average molecular weight (Z均分子量): (4) Viscosity-average molecular weight (粘均分子量): Schulz Tung Logarithm normal distribution 用简化的函数拟合 Width of molecular weight distribution (分子量分布宽度): Polydispersity (多分散系数): MW Distribution Function 实验测量 平均分子量 分布宽度 End group analysis (端基分析) molecular weight determination through group analysis requires that the polymer contain a known number of determinable groups per molecule. measure the number-average molecular weight, Mn ? 2.5 ? 104 Colligative property (依数性) measurement: measure the number-average molecular weight Mn vapor-pressure lowing boiling-point elevation (ebulliometry) freezing-point depression (cryoscopy) osmotic pressure (osmometry) DTb, DTf, an