Structure and Electrostatic Interaction Properties of Monolayers of Amphiphilic Molecules Derived from C₆₀-Fullerenes:  A Film Balance, Neutron-, and Infrared Reflection Study

Abstract

Monolayers at the air/water interface of a new amphiphilic molecule derived from a C60-fullerene were studied at different lateral pressures by a combination of film balance techniques, neutron reflection (NR), and infrared reflection−absorption spectroscopy (IRRAS). The amphiphilic fullerene derivative (AF) consisted of a dendrimeric hydrophilic region, and 10 alkyl chains covalently attached to the fullerene cage formed the hydrophobic part. The AF monolayers could be compressed and expanded without significant hysteresis and the alkyl chains remained fluid at all pressures. By a titration series, the pK value of the AF monolayer was determined as 7.5 and pH dependent measurements allowed a variation of the negative AF headgroup charge by about 18 charges. The thickness of the AF monolayer at high lateral pressure was 30 Å, thus similar to that of typical phospholipid monolayers in the condensed state. In contrast, the AF molecular area was about 6-fold higher than that of phospholipids at high pressure. Moreover, the hydration capacity of the AF headgroup is significantly higher than that of phospholipids. The negatively charged AF monolayer showed a strong coupling of the water-soluble protein cytochrome c from the subphase, leading to the formation of a 30 Å thick protein layer underneath the AF layer. The protein content of this layer varied drastically with the pH value. The properties of the AF monolayers may be useful in the design of dedicated biomimetic surfaces.

Amphiphilic [5:1]‐ and [3:3]‐Hexakisadducts of C60

“…Recently, we introduced two examples, 1 [1,2] and 2, [3Ϫ5] of amphiphilic [5:1]-hexakisadducts of C 60 that involve an octahedral addition pattern. [6] The remarkably facile access to these stereochemically defined multiple adducts required control over the regioselectivity of the subsequent additions to the [6,6]-bonds in equatorial sites.…”

Fullerene‐Containing Liquid Crystals

“…In the field of C 60 materials science, studies deal with the self-organization of molecules having original ordered structures [1][2][3][4] and mainly thermotropic or lyotropic liquid-crystalline mesophases, micelles, membranes, or mono-and multilayered films [5][6][7][8][9][10]. However, the development of functional devices very often requires dedicated engineering of the molecules, that is, functionalization of the molecules for controlling their self-organization.…”

Spreading behaviour of a series of amphiphilic [3 : 3] [60]fullerene hexakisadducts: a systematic study

“…Both the SAM approach, achieved through junction moieties such as organosilane [16], organosulfur [17], or carboxylic acid [18], and the Langmuir technique allow control of the formation and the structure of the resulting film at a molecular level. In the latter field, working at the air-water interface, various [60]fullerene derivatives ranging from mono- [19][20][21][22][23][24][25], to bis- [26], up to hexa-adducts [27][28][29][30] have been studied in the past few years and showed encouraging results in terms of film quality and stability, roughness, reversibility, and transfer onto solid substrates. For example, Cardullo et al [31] or more recently Hirano et al [32] showed that fullerene mono-adducts bearing dendritic branches display good spreading characterisitics and reversible compression/ expansion behaviour has been described.…”

“…In this case, the C 60 units are buried in the middle of the dendrimer which provides an insulating layer around them, thus preventing the irreversible three-dimensional aggregation resulting from fullerene-fullerene interactions [39,40]. Finally, various studies performed very recently on [60]fullerene hexakisadducts [27][28][29][30] showed that hexa-addition on the carbon sphere provided not only an ideal structure to prevent aggregation phenomenon but also an optimised hydrophilic-hydrophobic balance for preparing well-ordered supramolecular assemblies at the air-water interface.…”