The rôle of the chain length in the stability of polyion complexes

To demonstrate the cooperativity in the formation of an interpolymer complex, the stability of polyanion‐polycation complexes as a function of their chain length was studied. Poly(methacrylic acid) (PMAA; P̄n ≈ 800) was used as source for the polyanion and quaternized alkylamines and polyethyleneimines with various chain lengths (1a–g and 2a–g) as source for the polycation. The reaction was followed by the measurement of [H+] from which the stability constants (K) of the complexes were calculated. It was found that the K‐values increased exponentially from 102 to 8.104l mol−1 with increasing chain length of the polycation. Furthermore, it was found that, in addition to COULOMBic forces, the hydrophobic interaction plays an important rǒle in the complexation.