Incorporation of Copper (II) Phtalocyanines as Model Dyes in Exponentially Growing Polyelectrolyte Multilayer Films: A Multiparametric Investigation

The incorporation of two different copper (II) phtalocyanines differing in their charged groups (sulfonato versus pyridino) in exponentially growing polyelectrolyte multilayer films (PEMs) made either from poly-l-lysine (PLL) and poly-l-glutamic acid (PGA) or from PLL and sodium hyaluronate (HA) has been investigated. The motivation of our study was to investigate the influence of different parameters on the ability of a molecule of constant size but differing in its charge to incorporate in and to be released from PEMs. The investigated parameters were: the nature of the last deposited polyelectrolyte, the ionic strength of the solution, and the nature of the polyanion present in the film (PGA versus HA). Complementarily, we have investigated the simultaneous or the consecutive incorporation of two anionic species, the anionic phtalocyanine and Ti(IV) (bislactato dihydroxyde) in (PLL−HA)n films: the incorporation of both species was possible only if they were put in competition during their incorporation in the film, but if the films were saturated by one of the species, the subsequent incorporation of the second one was not possible anymore. Overall our findings show that exponentially growing PEMs having a positive Donnan potential can be used to incorporate negatively charged copper phtalocyanines at very high concentrations, whereas the positively charged counterparts are totally excluded. In addition, our data show that the negatively charged phtalocyanines are not homogeneously incorporated through the whole thickness of the PEMs.