Macroscopic and nanoscopic current−voltage measurements reveal asymmetries in the DC electrical conductivity through Langmuir−Blodgett multilayers and even monolayers of γ-(n-hexadecyl)quinolinum tricyanoquinodimethanide, C16H33Q-3CNQ (5). These asymmetries are due to a transition of the ground-state zwitterion to an excited-state conformer which is probably neutral. Unimolecular electrical rectification by monolayers of 5 is unequivocally confirmed.

An increase in random molecular vibrations of a solid owing to heating above the melting point leads to a decrease in its long-range order and a loss of structural symmetry. Therefore conventional liquids are isotropic media. Here we report on a light-induced isothermal transition of a polymer film from an isotropic solid to an anisotropic liquid state in which the degree of mechanical anisotropy can be controlled by light. Whereas during irradiation by circular polarized light the film behaves as an isotropic viscoelastic fluid, it shows considerable fluidity only in the direction parallel to the light field vector under linear polarized light. The fluidization phenomenon is related to photoinduced motion of azobenzene-functionalized molecular units, which can be effectively activated only when their transition dipole moments are oriented close to the direction of the light polarization. We also describe here how the photofluidization allows nanoscopic elements of matter to be precisely manipulated.

The specialized‐performance polymers poly(arylene‐1,3‐oxadiazole)s—see Figure for an example—have high‐value end uses based on their electronic, optical, and thermal properties. The syntheses, solid‐state structure, properties, and applications of poly(arylene‐1,3,4‐oxadiazole)s are reviewed. magnified image

Several rodlike 4,4‘‘-bis(decyloxy)-p-terphenyl derivatives incorporating nonionic hydrophilic groups in the lateral 2‘-position (2-oxa-4,5-dihydroxypentyl, 2,5-dioxa-7,8-dihydroxyoctyl, 2,5,8-trioxa-10,11-dihydroxyundecyl, and 2,5,8,11-tetraoxa-13,14-tetradecyl groups) and 2‘-(2-oxa-4,5-dihydroxypentyl)-4,4‘‘-diundecyl-p-terphenyl form well-ordered thin films when spread at the air−water interface. One observes two sharp breaks in the pressure/area isotherms separated by a large plateau. The first break occurs at an area of ca. 0.90 nm2/molecule, an area which corresponds to a side-on arrangement of the terphenyl units at the interface. The plateau corresponds to a first-order phase transition. The surface pressure related to this transition significantly rises with an increasing number of oxyethylene units in the hydrophilic lateral groups. Brewster angle microscopic investigations indicate the formation of fluid domains in this region. In some cases these domains coalesce to a homogenous layer. The surface potential is nearly constant in the region of the plateau, which can be explained by a defined collapse due to the formation of a triple layer consisting of a bilayer on top of the monolayer.

The performance and safety of rechargeable batteries depend strongly on the materials used. Lithium insertion materials suitable for negative and positive insertion electrodes are reviewed. Future trends, such as alternative materials for achieving higher specific charges—the Figure shows a scheme for reversible lithium storage in a high specific charge carbonaceous material—are discussed.

An apertureless optical near-field scanning microscope system has been created by combining a commercially available atomic force microscope and an ellipsometer without any prior changes in design of the respective devices. In preliminary experiments, an optical resolution of about 20 nm ͑/32͒ has been achieved using the combined microscope. The intensity of the measured optical signal has been found to be a periodic function of the thickness of the sample. Moreover, the period of this function is dependent upon the local optical properties of the sample material.

Short perfluorinated carbon chains do not take o n a helical structure when they are closely packed.

Photoelectron spectra were measured for films of self-assembled azobenzene-terminated alkanethiol monolayers on gold using synchrotron radiation. The azobenzene was substituted either by CF 3 or CH 3 in the para position. As a result of the orientational order of the molecules within the films, as indicated by the pronounced angle dependence of the photoemission spectra, it is possible to identify laser-induced optical switching of the molecules using combined laser and synchrotron pulses. Molecular switching, i.e., photoisomerization, is recognized by relative intensity changes of the photoemission peaks and also by spectral shifts to higher binding energies. The latter result from a change of the molecular dipole moment associated with the transcis laser-induced photoisomerization of the azobenzene-CF 3 group.