The monolayer polymorphism of hexadecyl and octadecyl urea

Glazer, J.; Alexander, A. E.

doi:10.1039/tf9514700401

Cited by 50 publications

(30 citation statements)

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“…7 The temperature dependence of the entropy change ΔS = ΔH/T for the phase transition is presented in Figure 4B. Negative ΔH and ΔS values are obtained according to the exothermic nature of the main phase transition at compression of amphiphilic monolayers and an increase in the ordering of the system.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Monolayer Properties of 1,3-Diamidophospholipids

2013

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While nature provides an endless variety of phospholipids presenting hydrolyzable ester linkages for the 1,2-positioned hydrocarbon tails, we designed and synthesized 1,3-diamidophospholipids which contain stable fatty acid amides. These new phospholipids form faceted unilamellar vesicles with mechanosensitive properties. Aiming to understand the mechanism responsible for this behavior at a molecular level, we investigated the 1,3-diamidophospholipid family in monolayers, a simplified model membrane system. Langmuir isotherms combined with in situ grazing incidence X-ray diffraction (GIXD), specular X-ray reflectivity (XR), and infrared reflection−absorption spectroscopy (IRRAS) allowed the characterization of the monolayers from a structural and thermodynamical point of view. The existence of strong headgroup interactions due to the formation of a hydrogen-bonding network was clearly revealed by IRRAS and by the high rigidity of the monolayers. GIXD showed that only the longer chain compounds of the series (Pad-PC-Pad (1,3-dipalmitamidopropan-2-phosphocholine) and Sad-PC-Sad (1,3-distearamidopropan-2-phosphocholine) were able to form ordered monolayers. The chains are strongly tilted in a rigid lattice formed due to these hydrogenbonding interactions between the headgroups. The thermodynamical analysis leads to a critical temperature of the monolayer which is clearly different from the main phase transition temperature in bulk, indicating that there must be a different structural arrangement of the 1,3-diamidophospholipids in monolayers and in bilayers.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Monolayer Properties of 1,3-Diamidophospholipids

2013

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“…Octadecylamine forms a more expanded monolayer since the molecules are partly ionized at pH 6, leading to electrostatic repulsion between the RNH + 3 headgroups (19). Octadecylurea is able to form two distinct solid phases (α-/β-phase) which differ significantly in molecular area and could be transformed into each other by varying the temperature or the surface pressure (20).…”

Section: Resultsmentioning

confidence: 99%

“…• (20,30). At the transition point either the temperature or the surface pressure are sufficient to initiate the disruption of the hydrogen bonds, and the head groups as well as the hydrocarbon chains start rotating into a vertical position, forming a considerably condensed film (31).…”

Section: Discussionmentioning

confidence: 99%

Molecular Interactions in Mixed Monolayers of Octadecanoic Acid and Three Related Amphiphiles

Stosch

Cammenga

2000

Journal of Colloid and Interface Science

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“…[60][61][62][63][64] Urea is chosen as the hydrophilic head because the monolayer of alkylureas shows interesting characteristic properties attributed to the formation of so-called bifurcated (double) hydrogen bond among the urea units on water. [65][66][67][68] When urea is connected with Az unit, further interesting behavior appears as follows. 1) The trans-to-cis photoisomerization of Az is completely hindered at the air-water interface despite the fact that the absorption maximum of the -Ã band almost coincides with that in solution.…”

Section: Supramolecular Approach Using Urea Derivativesmentioning

confidence: 99%

Dynamic Photoresponsive Functions in Organized Layer Systems Comprised of Azobenzene-containing Polymers

Seki

2004

Polym J

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ABSTRACT:Azobenzene (Az)-containing polymers provide fascinating photoresponsive actuation systems. When they are organized at interfaces, the motion of Az unit occurring at a molecular (sub-nano) scale can be transferred and amplified to larger scales of materials. This review article focuses to selected research topics on organized layer systems of Az-containing polymers proceeding in our laboratory. They involve i) photomechanical response of monolayers at nanometer levels in thickness and centimeters in area, ii) monolayer-mediated photoorientation of polymer (polysilane) and mesoporous silica at nano-to sub-micrometer levels in thickness, and iii) instant mass migration triggered by patterned photoirradiation occurring at distances over micrometer levels. In every system, strong cooperative interplays between the Az unit and organized molecular or macromolecular assemblies play the essential roles. Promotions of these research areas are anticipated to provide wide and new opportunities for material processing and creation of new classes of photofuncitional soft materials.

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The monolayer polymorphism of hexadecyl and octadecyl urea

Abstract: The monolayer behaviour of some long chain ureas has been investigated and discussed in terms of monolayer structures involving intermolecular N-H . . . 0 hydrogen bonds. A new ( y ) monolayer form of octadecyl urea

Cited by 50 publications

References 0 publications

Monolayer Properties of 1,3-Diamidophospholipids

Monolayer Properties of 1,3-Diamidophospholipids

Molecular Interactions in Mixed Monolayers of Octadecanoic Acid and Three Related Amphiphiles

Dynamic Photoresponsive Functions in Organized Layer Systems Comprised of Azobenzene-containing Polymers

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