Assoziation von Makromolekülen

Abstract

Methods to determine the association of macromolecules and to calculate the molecular weight of the unimer M_I, the equilibrium constant of association and the virial coefficients for different models are discussed, Association is defined as a reversible combination of molecules to larger particle units and is to be distinguished from aggregation involving an irreversible process. Association can be observed in good solvents, i. e. for positive second virial coefficients, too. Formulas are derived for the two limiting cases of association, closed association N M_I ⇄ M_N, and open association with the consecutive processes 2 M_I ⇄ M_II, M_II + M_I ⇄ M_III, etc. and identical equilibrium constants for all steps, which enable the calculation of molecular data from the concentration dependance of apparent molecular weights for number average and weight average methods. Molecular motives for the association processes are discussed on the basis of available literature data.