Flavin adenine dinucleotide (FAD) undergoes multisite
molecular recognition at the air-water interface
with mixed monolayers that are capable of complementary hydrogen
bonding. Molecular images were
obtained with an atomic force microscope (AFM) for mixed monolayers of
guanidinium (G) and orotate (O)
amphiphiles transferred from pure water and from aqueous FAD. The
AFM image of the G/O mixed
monolayer on FAD showed a periodic oblique pattern composed of two
kinds of methyl peaks with different
heights, whereas that on pure water showed a periodic hexagonal pattern
of only one kind of methyl peak.
The two-dimensional molecular patterning as height difference is
conceivably caused by rearrangement
of monolayer components based on specific recognition by the FAD
template molecule.
A two-dimensional ultrathin film was defined as a film with a dimension thinner than that of an unperturbed chain. The aggregation structure of the two-dimensional ultrathin polystyrene (PS) film prepared by the water casting method was examined. The radius of gyration of a PS chain in the twodimensional ultrathin film was evaluated from small angle X-ray scattering (SAXS) and small angle neutron scattering (SANS) measurements. The radius of gyration along the direction parallel to the film surface was found to be larger than the radius of gyration of an unperturbed chain. The apparent occupied volume for a corresponding chain, which consists of overlapping of a noticed chain and surrounding chains, was calculated from the radius of gyration and film thickness. The apparent volume in the two-dimensional ultrathin film was found to be smaller than that in the three-dimensional solid film, indicating that the amount of interpenetration of surrounding chains is small; that is, the degree of entanglement among chains is low. A PS chain with a low degree of entanglement in the two-dimensional ultrathin film was expanded along the direction parallel to the film surface owing to unequilibrium characteristics of the film formation process. The radial distribution function (RDF) in the two-dimensional ultrathin film was also obtained from the Fourier transform of the wide angle X-ray scattering profile. The shape of the peak corresponding to intermolecular distance in the two-dimensional ultrathin film was broadened toward the long distance side, indicating that the packing of PS chains in the two-dimensional ultrathin film was looser than that in the three-dimensional solid film.
A monolayer of 2-amino-4,6-di(dodecylamino)-1,3,5triazine 1 transferred from barbituric acid solution onto a mica plate is observed by atomic force microscopy (AFM) to show regularly arrayed terminal methyl groups of 1 as a result of hydrogen-bond networking.We have recently reported multisite molecular recognition between multicomponent monolayers on water and flavin adenine dinucleotide (FAD) in water. 1 This result opened the possibility to control the alignment of component amphiphiles within a monolayer.2 We extended this concept one step further in the present study and examined extended hydrogen-bond network formation between a monolayer of 2-amino-4,6-di(dodecylamino)-l,3,5-triazine 17 and aqueous barbituric acid.
Morphological change of a micelle of poly(styrene)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-PVP-PEO) polymer was induced by binding sodium dodecyl sulfate (SDS) to the PVP block in acidic aqueous solutions. The change in the size of SDS/PS-PVP-PEO complexes was detected by dynamic light scattering measurements and atomic force microscopy, and the binding of SDS was confirmed by zeta-potential measurements. When the micelle was free from SDS in acidic aqueous solutions, the hydrodynamic diameter of the micelle was 216 nm, reflecting the extended conformation of the PVP block due to the repulsion between protonated pyridine units. As the cationic PVP block was electrically neutralized with anionic SDS, the diameter was gradually reduced concomitant with the decrease in zeta-potential and finally reached 175 nm when the PVP block was completely neutralized. The decrease in the diameter shows the morphological change of the PVP block from extended to shrunken forms. Further addition of SDS did not cause the changes of the diameter nor zeta-potential. This indicates that SDS was not bound to the PS-PVP-PEO polymer after the PVP block was fully neutralized and that the hydrophobic binding of SDS to the polymer was negligible due to the low concentration of SDS.
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