wikipedia: In organic chemistry, the polydispersity index (PDI), is a measure of the distribution of molecular mass in a given polymer sample. The PDI calculated is the weight average molecular weight divided by the number average molecular weight. It indicates the distribution of individual molecular masses in a batch of polymers. The PDI has a value equal to or greater than 1, but as the polymer chains approach uniform chain length, the PDI approaches unity (1).

从数学角度看大于等于1.

聚合物，用凝胶色谱测PDI，就是分子量分布情况，当然越低越好啦！也就是说越接近1越好！如果用DLS（动态光散射）的粒经分布，应该也是越小越好，不过这个值都是小于1的。

PDI肯定是大于1的，即使是GPC标样，PDI也不过是小于1.1。

凝胶色谱就好了，没有问题了。

动态光散射结果是接近零最好，一般都小于0.1