gpc分子量及分子量分布测量.ppt

* 讲一些关于各个公司利用液相色谱外加GPC组件完成GPC功能，检测器的温度稳定性，进样器的进样体积和液相色谱不同 * The concentration detector responds to concentration, C. The RI detector responds to C times the specific refractive index increment, dn/dc. The MW sensitive detectors respond to MW times some function. For viscometers, this function is [n], the intrinsic viscosity. For light scattering, the response is simply M(C), and for mass spectrometry, the response is 1/M. This is why mass spec. is not very useful for high MW polymers. * For a given MW, a branched polymer will have a lower intrinsic viscosity and smaller size. We can ratio the the I.V. of the branched polymer at every slice point relative to a linear counterpart, and obtain the branching index, g’. This value will be less than one for a branched polymer and will be = 1 for a linear polymer. The overall g’ may be expressed as the product of the g’ for short chain branching (SCB) and long chain branching, (LCB). * A linear polymer may be described by the linear MH plot, with a single alpha. A polymer with short chain branching also has a linear plot, but with a slightly lower intercept, (K). This is because the short chain branches will result in a slightly lower I.V. than the linear counterpart. The branching index, g’, will be constant, independent of MW. * Illustration of previous slide. * Individual pore size columns give the best resolution over a small operating range – maximum pore volume over a few decades o molecular weight. MIXED columns give equal resolution over a much larger operating range, better if you are not sure of the molecular weight of your sample. 实验证明这种方法对线性和无规线团形状的高分子普适性较好，而对长支链和棒状刚性高分子的普适性还需要进一步研究。 普适校正曲线 两种校正曲线的比较 方法 单分散标样 校正曲线 普适校正曲线 优点 方法简便，准确性高 可以用一种标样得到的校正曲线测定其它聚合物的分子量及其分布 缺点 难以获得与待测样品同类的单分散标样，而且只能测定与标样同类的聚合物 必须已知待测聚合物的K和α值 分子量及其分布的计算 单分散性样品 只要测出GPC谱图即可由淋洗体积求出分子量 多分散性样品的分布 函数法 选择一种能描述GPC曲线的函数，根据此函数算出平均分子量，应用最多的是高斯分布函数 MP和σ分别为峰位分子量和谱峰宽度，B1＝2.303B 条块法 当谱图不对称或出现多峰时应用此法。将GPC曲线沿横坐标分成n个级分，求出每个级分的淋洗体积Vi和浓度Hi，再由校正曲线求出每个