Oligofunctional amphiphiles featuring geometric core group preorganization: synthesis and study of Langmuir and Langmuir–Blodgett films

Abstract

Based on the principle of supramolecular preorganization, a new type of oligofunctional amphiphile, of which compounds 1-4 are representative structures, has been designed and synthesized. The typical feature of their structure is a highly rigid and geometrically well-defined central unit composed of ethynylene substituted aromatic spacers with different numbers of amphiphilic segment groups (also of a rigid geometric design) attached to it. The molecules form well-defined Langmuir films when spread from a solution at the air/water interface or when a 10(-4) M aqueous CaCl2 solution was used as the subphase. By analysis of the surface pressure-surface area (pi-A) isotherms, information on the packing behavior and orientation of the amphiphilic molecules depending on the molecular structure could be obtained. Morphological characterization of the dynamic process of monolayer compression at the air/water interface was carried out by Brewster angle microscopy, illustrating several phase states visualized as snap shots. Thin monolayer films produced on a 10(-4) M aqueous CaCl2 subphase can be transferred to a mica solid support by the Langmuir-Blodgett technique. Tapping mode atomic force microscopy reveals a surface topography of the monofilms composed of 1 and 3 that differ in roughness and also in the properties of elasticity, hardness and adhesive strength. X-Ray crystal structure analysis of three relevant intermediate compounds of the synthesis were successfully determined giving an indication of the potential structural features inherent in the new amphiphiles.

A Dendritic Amphiphile for Efficient Control of Biomimetic Calcium Phosphate Mineralization

“…The isotherms recorded on a 200 × 10 −3 m calcium nitrate subphase show the same trend, but the collapse of the film already occurs at a surface pressure of 45 mN m −1 which is almost 20 mN m −1 lower compared to the lower concentrations. Several studies have shown that bivalent metal ions such as Ca 2+ have the ability to stabilize the amphiphile monolayer due to the interaction of the metal ions with two carboxylic groups . In this study, we do not observe this type of monolayer stabilization.…”

“…Several studies have shown that bivalent metal ions such as Ca 2+ have the ability to stabilize the amphiphile monolayer due to the interaction of the metal ions with two carboxylic groups. [53,54] In this study, we do not observe this type of monolayer stabilization.…”

An Efficient Synthesis of Substituted meta‐Halophenols and Their Methyl Ethers: Insight into the Reaction Mechanism

“…Substituted meta ‐halophenols are valuable intermediates in organic synthesis, having been found to be useful both in materials science18 and in the pharmaceutical industry 19. Müller et al utilized the ethyl ester analogue of 10f as a functionalized building block for the construction of multifunctional molecular materials such as preorganized oligofunctional amphiphiles18 and a thrombin inhibitor was successfully synthesized by Lu et al through employment of the benzyl ester derivative of the chloro analogue of 10f 19…”

Synthesis, Langmuir and Langmuir–Blodgett film behaviour of new dendritic amphiphiles

“…Bivalent metal ions are well known to interact with carboxylic groups of several amphiphiles, frequently resulting in improved Langmuir or LB film stability. 1a,17b From a previous report, 8 one may expect that the presence of Ca 2+ ions in the aqueous subphase, such as with a 10 À4 M aqueous CaCl 2 subphase in comparison with a pure water subphase, will have a bearing on the required area per molecule of carboxylic acid amphiphiles and will stabilize the Langmuir monolayer, through the bivalent cation interaction with two carboxylic groups. However, the amphiphiles discussed here do not adhere strictly to this expectation but behave differently in some cases, i.e.…”

“…a geometrically well-defined central building block composed of ethynylene substituted aromatic spacers, with different numbers of amphiphilic segment groups, which are also of rigid geometric design, was used. 7,8 Another topical concept of supramolecular chemistry, which is the strategy of multiple branching, has also been introduced into the design of new surfactant structures, yielding dendritic amphiphiles. 9 The multiple branching results in organic molecules with interesting properties and in highly stable non-crystalline supramolecular architectures.…”