Article

# Shape and stability of two-dimensional lipid domains with dipole-dipole interactions.

Department of Physical Electronics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8552, Japan.

The Journal of Chemical Physics (Impact Factor: 3.12). 01/2007; 125(22):224701. DOI: 10.1063/1.2402160 Source: PubMed

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**ABSTRACT:**Study of Langmuir monolayers consisting of stearic acid (SA) and dipalmitoylphosphatidylcholine (DPPC) molecules was done by surface pressure–area isotherms (π–A), the Maxwell displacement current (MDC) measurement, X-ray reflectivity (XRR) and atomic force microscopy (AFM) to investigate the selected mechanic, thermodynamic and dielectric properties based on orientational structure of monolayers. On the base of π–A isotherms analysis we explain the creation of stable structures and found optimal monolayer composition. The dielectric properties represented by MDC generated monolayers were analyzed in terms of excess dipole moment, proposing the effect of dipole–dipole interaction. XRR and AFM results illustrate deposited film structure and molecular ordering.Applied Surface Science 08/2008; 254(20):6370–6375. · 2.54 Impact Factor -
##### Article: KIDNEY-BOOJUM-LIKE SOLUTIONS AND EXACT SHAPE EQUATION OF SOLID-LIKE DOMAINS IN LIPID MONOLAYER

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**ABSTRACT:**The shape of solid lipid monolayer domain surrounded by a fluid phase is of considerable interest from physical and mathematical points of view. Here we report two new results about this topic. First, we obtain an exact analytical solution to an approximated shape equation that was derived by us recently [Phys. Rev. Lett. 93, 206101 (2004)]. This solution can well describe the kidney- and boojum-like domains that abound in lipid monolayer. Second, we derive an exact domain shape equation by a direct variation of domain energy without any artificial cutoff. We find that no continuous solutions satisfies this shape equation due to the divergence of its coefficients, which is rooted in the continuous description of electrostatic dipoles.International Journal of Modern Physics B 01/2012; 22(25n26). · 0.46 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Probing and modeling of dynamical motions of electrons and dipoles in materials is a fundamental research subject in science and electronics. By probing dielectric polarization phenomena induced by dipoles and electrons, carrier motions in materials are visualized. Maxwell's displacement current (MDC) directly probes orientational dipolar motion in monolayes. Electric field induced optical second harmonic generation (SHG) directly probes electron and hole motions in materials. In this presentation, at first, basic concept for probing dynamical carrier motions as dielectric polarization phenomena is discussed. Then some of experimental results are demonstrated, and carrier motions in OFET, OLED and OSCs are visualized and modeled. Results show that carrier transfer in OFET is governed by the interface charging propagation, and Maxwell's Wagner type interfacial charging makes a dominant contribution to the performance of Organic light-emitting diodes (OLEDs), OFET and OLEDs. MDC experiments coupled with BAM method visualizes quantized domain shape of dipolar monolayers. Finally, the importance of dielectrics physics approach is stressed as an effective way for analyzing carrier dynamics in organic electronics.06/2012;

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