Studies on the structure and miscibility of mixed Langmuir–Blodgett films of a double-armed dibenzo-18-crown-6 ether with stearic acid

Phase separation in mixed monolayers of arachidic acid and a phthalocyanine of zinc

“…Both sets of values agree, indicating definitively that AA and tbuPcZn form separate phases and that are immiscible. Immiscibility has also been observed by Peng et al [5] in mixed films of cadmium arachidate (CdAr) and a porphinatocopper(II), but Cheng et al [12] have found no phase separation in the mixed films of stearic acid (SA) and a crown ether, a fact that was attributed to the possibility that SA molecules can enter into the crown ether ring. Our system behaves more similarly to that of Peng et al [5].…”

“…Some authors [1,12] have reported that for other mixtures of dissimilar components, an amphiphilic long-chain compound and a macrocycle with long-chain substituents, on compression the longchain compound disposes itself on top of the macrocycle layer, forming a two-layer film. But our observations point to a monolayer with two separate phases.…”

“…An increase in the area has also been observed in a mixed film of a thiomacrocyclic compound with AA [16,17], 3 which has been attributed to a partial solubility of AA in the thiomacrocycle phase with a loss of compactness, and in a mixed film of a nitrostilbene derivative with behenic acid [10], which has been attributed to the ability of behenic acid to prevent aggregation of the nitrostilbene derivative. In other cases a decrease in the area per molecule has been observed [9,12], which has been attributed to the fact that fatty acid molecules can enter into the macrocyclic ring [12] or to the formation of a condensed phase [9]. Other authors [13] have found that the miscibility of an azacrown ether with palmitic acid depends on the surface pressure, and reported that miscibility occurs at intermediate pressures, at least on the macroscopic level based on the BAM observation of film homogeneity.…”

“…The study of mixed films of dissimilar components [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] is of practical interest due to the fact that a great number of compounds of technological interest need a film former. Phthalocyanines (Pc), porphyrins (P), metallo-porphyrins (MP) and metallophthalocyanines (MPc) are an example.…”