What is the molecular weight of an ion exchange resin?
An ion exchange resin is a three-dimensional polymeric matrix. The polymer matrix is made up of monomers cross-linked with divinylbenzene. It is made in a bead form which is then converted into the corresponding powder by grinding. Because of the high degree of cross-linking a single particle is essentially a single molecule and so has an extremely high molecular weight. Because the resins are completely insoluble in all solvents it is not possible to measure the molecular weight independently. Furthermore, because each particle is one molecule, the concept of polydispersity is meaningless for ion exchange resins. Within a particle the polydispersity is 1 (a single molecule). Molecular weight will depend on particle size and has been estimated by calculation to be of the order of 1018. To avoid possible confusion, however, it should be noted that the resins do contain some low molecular weight polymer impurity formed as a by-product of the grinding process. This polymer can be extracte
