Mixing Processes in Binary Monolayers Induced by the Spreading Solvent

Rettig, W.; Dörfler, H.‐D.

doi:10.4028/www.scientific.net/msf.25-26.577

Cited by 2 publications

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“…These previous results suggested formation of DMPI aggregates that are subsequently pushed out of the air−water interface to remain partly sandwiched between the SA chains or squeezed out of the film onto its surface. These results are consistent with the fact that DMPI molecules are physically and chemically different from the host matrix SA, and hence it is likely that they do not tend to solubilize in the SA microphase but tend to form aggregates and phase separate …”

Section: Resultssupporting

confidence: 85%

Spectroscopic, AFM, and NSOM Studies of 3D Crystallites in Mixed Langmuir−Blodgett Films of N,N‘-Bis(2,6-dimethylphenyl)-3,4,9,10-perylenetetracarboxylic Diimide and Stearic Acid

et al. 1998

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Nonamphiphilic N, 4,9, has been incorporated in Langmuir-Blodgett (LB) films mixed with stearic acid (SA). Steady-state spectroscopic studies of the LB-deposited films on quartz substrates indicate an extensive broadening and shift of the absorption and emission spectra, suggesting molecular aggregation. Perhaps the most interesting spectral feature observed in this study is the observation of a broad emission band with its maximum at 650 nm. Concentration dependent studies demonstrate that, with increasing mole fraction of DMPI in the mixed film, the broad band emission at 650 nm increases in intensity while the higher energy band at 570 nm decreases. Excitation spectra corresponding to the two emission bands at 570 and 650 nm are observed to be different, indicating that the species corresponding to the emission at 570 and 650 nm are different. One plausible explanation is that the band at 570 nm corresponds to the monomeric species while the band at 650 nm corresponds to an aggregate. Near-field scanning optical microscopy (NSOM) of the mixed LB films shows granular structures in addition to flat, irregular-shaped, terrace-like structures. Detailed studies confirm these structures to be three-dimensional. A close examination of the NSOM topographic and fluorescence scans as well as atomic force microscopy (AFM) studies shows that these granular structures are crystallites of DMPI. On the other hand it is confirmed that the flat, irregular-shaped structures, that are nonfluorescent and absent in the NSOM fluorescence scans, are indicative of SA multilayers. These studies confirm the formation of three-dimensional crystallites of the dye formed in the LB films due to phase separation of the components, which suggests low miscibility of the components.

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Section: Resultssupporting

confidence: 85%

Spectroscopic, AFM, and NSOM Studies of 3D Crystallites in Mixed Langmuir−Blodgett Films of N,N‘-Bis(2,6-dimethylphenyl)-3,4,9,10-perylenetetracarboxylic Diimide and Stearic Acid

et al. 1998

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Spectroscopic Study of Nonamphiphilic 2,2‘-p-Phenylenebis(5-phenyloxazol) (POPOP) Assembled in Supramolecular Langmuir−Blodgett Films

Dutta

1997

J. Phys. Chem. B

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This paper reports the incorporation of a nonamphiphilic blue laser dye 2,2′-p-phenylenebis(5-phenyloxazol), abbreviated as POPOP, in Langmuir-Blodgett (LB) films mixed with stearic acid (SA) and their spectroscopic properties. The surface pressure versus area per molecule isotherms of POPOP mixed with SA at different molar ratios reveal a plateau-like region that suggests reorientation of the POPOP molecules from lying flat at the air-water interface to an almost vertical alignment. Miscibility studies indicate a repulsive type of interaction between the components in the mixture, resulting in the formation of microcrystallites in the LB films that is confirmed by spectroscopic studies. Perhaps the most interesting feature of this study is the appearance of a new band at about 400 nm in absorption spectra of the mixed LB film of POPOP and SA that is assigned to a low-lying hidden 1 L b state. The appearance of the same band in a mixture of ethanol and water with the volume fraction of water in the mixture exceeding 76% confirms that the manifestation of this band is aggregation induced. Fluorescence emission studies of POPOP in solution reveal a structured emission that originates from the 1 L a state, while the emission studies from the LB films exhibit two bands, one at 420 nm originating from the low-lying 1 L b state of the monomer and the other at 460 nm corresponding to a 1 L b dimer. Excitation and polarized anisotropy measurements confirm these findings and indicate that the above observations may be attributed to a deformed geometry of the POPOP molecules in the LB films.

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Mixing Processes in Binary Monolayers Induced by the Spreading Solvent

Cited by 2 publications

References 0 publications

Spectroscopic, AFM, and NSOM Studies of 3D Crystallites in Mixed Langmuir−Blodgett Films of N,N‘-Bis(2,6-dimethylphenyl)-3,4,9,10-perylenetetracarboxylic Diimide and Stearic Acid

Spectroscopic, AFM, and NSOM Studies of 3D Crystallites in Mixed Langmuir−Blodgett Films of N,N‘-Bis(2,6-dimethylphenyl)-3,4,9,10-perylenetetracarboxylic Diimide and Stearic Acid

Spectroscopic Study of Nonamphiphilic 2,2‘-p-Phenylenebis(5-phenyloxazol) (POPOP) Assembled in Supramolecular Langmuir−Blodgett Films

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