2017 年 66 巻 5 号 p. 479-489
The interfacial behavior of binary monolayers of 1,1’-(1,ω-alkanediyl)-bispyridinium perfluorotetradecanecarboxylate (CnBP(FC14)2, n = 2, 6, or 10) and dipalmitoylphosphatidylcholine (DPPC) was studied using surface pressure (π)–area (A) and surface potential (ΔV)–A isotherm measurements and morphological observations. In a previous study, we showed that the spacer moieties of C2BP(FC14)2 and C6BP(FC14)2 are completely dissociated after spreading on 0.15 M NaCl, whereas the C10BP(FC14)2 spacer moieties do not dissociate in the monolayer state. However, in the present study, the ΔV–A isotherm indicated that the C10BP moiety partially dissociates in the presence of DPPC monolayers. The excess Gibbs free energy of mixing and two-dimensional phase diagrams suggest that CnBP(FC14)2 is miscible with DPPC monolayers and also has a fluidizing effect on DPPC monolayers. The phase behavior of the binary monolayers was observed with Brewster angle microscopy (BAM), fluorescence microscopy (FM), and atomic force microscopy (AFM). The dispersion mode of DPPC-rich domains by C10BP(FC14)2 is significantly different from those of the other CnBP(FC14)2 monolayers. These results suggest that the aliphatic chains in phospholipids control the dissociation of divalent spacers bound to fluorinated surfactants or amphiphiles.
