Direct observation by using Brewster angle microscopy of the diacetylene polimerization in mixed Langmuir film

Organization and structure of mixed Langmuir films composed of polydiacetylene and hemicyanine

“…Likewise, the BAM images of the amphiphilic hemicyanine dye HSP monolayer reveal inhomogeneous films. 16 However, three diffraction peaks at q xy = 1.38 Å -1 , 1.465 Å -1 , and, 1.577 Å -1 were obtained by G X π = 30 mN/m, see Figure 1 and Table 2. The mixed monolayer DA:HSP displays a phase transition at ca.…”

“…15 mN/m. 16 Prior to the phase transition, no micrometric structures were observed by BAM, whereas domains that grow with further increase of the surface pressure are detected after the phase transition, see inset in Figure 2. No GIXD signal was detected below 15 mN/m, before the phase transition.…”

“…Therefore, an emerging peak at 520 nm was detected, related to the formation of the red PDA polymer at the air/water interface. 16 The kinetics of the interfacial polymerization has been followed in situ by monitoring the GIXD peaks along the irradiation, see Figure 2 and Table 2. No GIXD signal was detected below 9.5 mN/m, before the phase transition.…”

“…No diffraction peaks corresponding to the isolated components have been observed for both DA:HSP and DA:SP system, which suggests the formation of mixed homogeneous Langmuir monolayers, confirming previous studies based on BAM and UV-vis reflection spectroscopy. 15,16 Despite the GIXD results cannot rule out a coexistent and disordered phase, Adjacent DA molecules are arranged with the diacetylene group and hydrophobic segments of each DA molecule in the same plane as the neighbor molecule, see scheme 2. The molecular model accounts for the molecular aggregation of the hemicyanine group as previously described by UV-vis reflection experiments.…”

“…The molecular model accounts for the molecular aggregation of the hemicyanine group as previously described by UV-vis reflection experiments. 16 Note the hemicyanine group of the HSP molecule has an -OH group that might contribute to the alignment of the rows of molecules through an aromatic hydrogen bond, see scheme 2A. 33 Such hydrogen bond cannot be present in the DA:SP mixed monolayer given the absence of the mentioned -OH group in the hemicyanine group of SP.…”