Association of Synthetic Polymers

Abstract

Abstract The methods available for a quantitative evaluation of solutions of associating macro-molecules are reviewed. Association is defined as a rapid equilibrium between unimers (non-associated molecules) and multimers (associated molecules) in homogeneous solutions. It can be subdivided into open and closed associations. Open associations are consecutive processes. Closed associations represent all-or-none processes. Both types of associations can be of either the end-to-end type (number of associogenic sites independent of molecular weight) or the segment-to-segment type (number of associogenic sites increasing with molecular weight in a polymerhomologue series). Relations between the polymolecularity of the unimers and the polydispersity of the multimers are given. Viscometry is shown to be no reliable method for the investigation of association if used alone without the knowledge of thermodynamic data. The equilibrium constants of macromolecules seem to be higher than those of low molecular weight materials of similar constitution under comparable conditions. The association of polypropylenes increases with increasing syndiotacticity. A possible influence of the order of the solvent and of the desolvation processes on the equilibrium constants of association is discussed. Poly(γ-benzyl-L-glutamates) form cyclic multimers in dilute solutions of certain solvents and solvent mixtures.