Multi-Dimensional Separations of Polymers

摘要

Synthetic polymers and comprehensive two-dimensional liquid chromatography (LC × LC) are a synergistic combination. LC × LC provides unique insights in mutually dependent molecular distributions. Synthetic polymers offer clear demonstrations of the value of LC × LC. Synthetic polymers (and many natural ones) have a relatively simple molecular structure. They often consist as linear chains of monomers (R). The structure of such macromolecules can be described by X(R)_nY, where X and Y are the end groups and n is known as the degree of polymerization. For a given polymer, with given end groups, the molecule is characterized completely if we measure n. There are a number of ways to measure the average degree of polymerization. These include colligative properties (such as osmotic pressure), light scattering, viscometry and, for low-molecular-weight polymers, spectroscopic techniques, such as NMR. However, many of the properties of polymers are strongly affected by the variation in molecular weights. Knowing the average molecular weight does not usually suffice. When you are contemplating wading through a river it helps little to know that it is one meter deep, on average.