Intramolecular crosslinking

When a high molecular weight polymer, in a solution of concentration above the critical concentration for entanglement, is lightly crosslinked to effect only a few bonds per macromolecule, its solution viscosity is significantly affected. The random coil model predicts a monotonous increase in viscosity as a function of crosslink density, leading to a fast gelation. The macromolecular domain model predicts that, under the same conditions, the viscosity will pass through a minimum before progressing to gelation. As the molecular weight of the polymer decreases, the differences between the models become indistinguishable. In this inquiry it is shown that at least the four polymers polyacrylamide, polyvinylalcohol, polyethyleneimine and high molecular weight epoxy (phenoxy), adhere to the prediction of the macromolecular domain model.