Phase diagram of coacervate complexes containing reversible coordination

Phase separation of coacervate complexes from cationic PDMAEMA [poly(N,N-dimethylaminoethyl methacrylate)] and anionic reversible coordination polymers are studied in the present work. The coordination polymers are formed from zinc and a bis-ligand L2EO4 [1,11-bis(2,6-dicarboxypyridin-4-yloxy)-3,6,9-trioxaundecane] and have variable chain length. The charge mixing ratio and metal-to-ligand ratio, M/L, are varied systematically, and the composition of the two coexisting phases is measured using 1H NMR and ICP-AES. The resulting phase diagram is asymmetric: the coacervate complex phase tolerates an excess of coordination polymer much more than an excess of the homopolymer. Moreover, the coacervate complex tends to choose the right amount of the three components under nonstoichiometric mixing conditions. Both the metal-to-ligand ratio (M/L ˜ 1) and charge ratio (f– ˜ 0.5) in the coacervate phase are around stoichiometry, leaving the excess components in the dilute phase.