Study of mixed Langmuir and Langmuir–Blodgett films of dissimilar components by AFM and force spectroscopy

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

“…As the number of domains and their total area increases with the AA percentage, we can assume that these high domains correspond to AA. The lower friction signal of AA domains was also observed previously [16] …”

“…Our system behaves more similarly to that of Peng et al [5]. An extra observation is that the AA domains decrease in size when the AA proportion increases from X AA =0.59 (mean diameter Ø=0.49 m) to X AA =0.74 (Ø=0.25 m), but for the X AA =0.833 the size increases again (Ø=0.44 m); a similar fact was also observed in other mixed films of AA with a different macrocycle [16], but for the moment the author does not have an explanation for these observations. Figure 4 shows the size distribution for the different compositions obtained from several AFM images; sizes do not present a perfect Gaussian distribution but there are some sizes around the mean 9 value with higher frequencies and it is also observed that the distribution for the mixed film with X AA =0.74 is less wide.…”

“…The AA domains have a height of around 0.7 nm in respect to the tbuPcZn phase. We have found in previous studies [16,40] a similar system but with a porphinatocopper, mixed with CdAr, which was obtained by using grazing incidence X-ray diffraction. These results contrast with that reported by Del Caño et al [7] in mixed films of titanyl(IV) phthalocyanine (TiOPC) and AA.…”

“…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].…”

“…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.…”