Studies of the structure and growth mode of dotriacontane films by synchrotron x-ray scattering and molecular dynamics simulations

Mo, H. J.; Trogisch, S.; Taub, H.; Volkmann, U.G.; Hansen, Flemming Yssing; Pino, Manuel del

doi:10.1088/0953-8984/16/29/005

Cited by 11 publications

(11 citation statements)

References 8 publications

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“…SEM was used for the visualisation of waxes in these and other studies of wax self-assembly and therefore the masses applied to the substrates must have been higher than necessary for SPM techniques used in more recent work. It is important for the interpretation of the results to note that the influence of a substrate could be lost after two or more layers of wax molecules have been formed on the substrate (Mo et al 2004). Another important point is that during in vitro crystallisation the concentration of wax molecules in the solvent increases when the solvent evaporates, and nucleation of the wax molecules might start within the solution without any influence of the substrate.…”

Section: Template-mediated Self-assemblymentioning

confidence: 99%

Structure–function relationships of the plant cuticle and cuticular waxes — a smart material?

Bargel

Koch

Cerman

et al. 2006

Functional Plant Biol.

282

206

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This paper is part of The EvansAbstract. The cuticle is the main interface between plants and their environment. It covers the epidermis of all aerial primary parts of plant organs as a continuous extracellular matrix. This hydrophobic natural composite consists mainly of the biopolymer, cutin, and cuticular lipids collectively called waxes, with a high degree of variability in composition and structure. The cuticle and cuticular waxes exhibit a multitude of functions that enable plant life in many different terrestrial habitats and play important roles in interfacial interactions. This review highlights structure-function relationships that are the subjects of current research activities. The surface waxes often form complex crystalline microstructures that originate from self-assembly processes. The concepts and results of the analysis of model structures and the influence of template effects are critically discussed. Recent investigations of surface waxes by electron and X-ray diffraction revealed that these could be assigned to three crystal symmetry classes, while the background layer is not amorphous, but has an orthorhombic order. In addition, advantages of the characterisation of formation of model wax types on a molecular scale are presented. Epicuticular wax crystals may cause extreme water repellency and, in addition, a striking self-cleaning property. The principles of wetting and upto-date concepts of the transfer of plant surface properties to biomimetic technical applications are reviewed. Finally, biomechanical studies have demonstrated that the cuticle is a mechanically important structure, whose properties are dynamically modified by the plant in response to internal and external stimuli. Thus, the cuticle combines many aspects attributed to smart materials.

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Section: Template-mediated Self-assemblymentioning

confidence: 99%

Structure–function relationships of the plant cuticle and cuticular waxes — a smart material?

Bargel

Koch

Cerman

et al. 2006

Functional Plant Biol.

282

206

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“…In the microscopic model proposed by Dignam and Fedyk, the film is adsorbed on an isotropic substrate and is considered to be a homogeneous twodimensional array of dipoles induced by an external electrostatic field and by the field originating from the induced dipoles in the other molecules. In our approximations, we only vary the molecular polarizability and maintain the number density and lattice parameter constant, because x-ray experiments 11,4 do not indicate considerable changes in both latter.…”

Section: Figmentioning

confidence: 99%

“…1,5,6 Although rotator phases have been studied in bulk crystals of alkanes, there are few reports of these phases in molecularly thin films. [7][8][9][10][11]16 Solid C32 films grown on SiO 2 surfaces have been found to follow the Stranski-Krastanov growth mode. At the substrate-alkane interface, there is a complete bilayer of molecules with their long axis parallel to the surface.…”

Section: Introductionmentioning

confidence: 98%

Crystalline-to-plastic phase transitions in molecularly thin n-dotriacontane films adsorbed on solid surfaces

Cisternas

Corrales

Campo

et al. 2009

The Journal of Chemical Physics

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Crystalline-to-rotator phase transitions have been widely studied in bulk hydrocarbons, in particular in normal alkanes. But few studies of these transitions deal with molecularly thin films of pure n-alkanes on solid substrates. In this work, we were able to grow dotriacontane ͑n-C 32 H 66 ͒ films without coexisting bulk particles, which allows us to isolate the contribution to the ellipsometric signal from a monolayer of molecules oriented with their long axis perpendicular to the SiO 2 surface. For these submonolayer films, we found a step in the ellipsometer signal at ϳ331 K, which we identify with a solid-solid phase transition. At higher coverages, we observed additional steps in the ellipsometric signal that we identify with a solid-solid phase transition in multilayer islands ͑ϳ333 K͒ and with the transition to the rotator phase in bulk crystallites ͑ϳ337 K͒, respectively. After considering three alternative explanations, we propose that the step upward in the ellipsometric signal observed at ϳ331 K on heating the submonolayer film is the signature of a transition from a perpendicular monolayer phase to a denser phase in which the alkane chains contain on average one to two gauche defects per molecule.

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“…[6][7][8][9][10][11][12][13][14] A thin film with a long chain of hydrocarbon molecule is also used as a model system for an organic molecular thin film. Many studies have been performed for many years using the hydrocarbon molecular film prepared by physical vapor deposition methods, such as vacuum evaporation.…”

Section: )mentioning

confidence: 99%

Structure of Normal Alkane Evaporated Films: Molecular Orientation

Nozaki

Saihara

Ishikawa

et al. 2007

jjap

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The molecular orientations of n-alkane (n-C 23 H 48 , n-C 24 H 50 , n-C 25 H 52 , n-C 26 H 54 and n-C 27 H 56 ) evaporated films prepared by considering various deposition conditions, including the type of substrate, substrate temperature, and evaporation rate, have been systematically investigated by X-ray diffraction analysis and scanning probe microscopy. Two typical molecular orientation states, namely, the "perpendicular orientation state", in which the molecular chain axes are perpendicular to the substrate surface, and the "parallel orientation state", in which the molecular chain axes are parallel to the substrate surface, are observed. At a high substrate temperature and a low evaporation rate, a "perpendicular (P) film", which consists of only the perpendicular orientation state, is obtained. At a low substrate temperature and a high evaporation rate, a "coexistent (C) film", which consists of both the perpendicular and parallel orientation states, is obtained. It is concluded, from the experimental results, that the most thermodynamically stable is the perpendicular orientation state. Furthermore, it is found that the molecular orientation behavior depends on the type of substrate and deposition time. These molecular orientation dependences are considered to be mainly due to a kinetic mechanism rather than the thermodynamic stability in the case of the evaporated film in this study.

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Studies of the structure and growth mode of dotriacontane films by synchrotron x-ray scattering and molecular dynamics simulations

Cited by 11 publications

References 8 publications

Structure–function relationships of the plant cuticle and cuticular waxes — a smart material?

Structure–function relationships of the plant cuticle and cuticular waxes — a smart material?

Crystalline-to-plastic phase transitions in molecularly thin n-dotriacontane films adsorbed on solid surfaces

Structure of Normal Alkane Evaporated Films: Molecular Orientation

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