Dear Colleagues

186(1-3) (2000), 135-141
A new class of ultrathin electro-optic films have been developed by the electrostatically self-assembled monolayer process. Using a simple ellipsometric technique, the electro- optic coefficients were measured as a function of the frequency of the applied electric field. The maximum of the coefficients is 600 pm/V. From these measurements, we deduce the orientational and the electronic contributions to the electro- optic modulation. At modulating frequencies lower than 20 Hz, the orientation dominates the electro-optic modulation process. At frequencies higher than 800 Hz, electrons are responsible for electro-optic behavior. (C) 2000 Elsevier Science B.V. All rights reserved.

[159] The Influence of Molecular-Weight over the Ultrathin Films of Biodegradable Polyion Complexes Between Chitosan and Poly(Gamma- Glutamic Acid)

W. Tachaboonyakiat, T. Serizawa, T. Endo and M. Akashi

Polym. J. 32(6) (2000), 481-485

Alternate adsorption is a well-known method for developing the novel. ultrathin films of biodegradable polyion complexes. This study revealed variations in the effect of chitosan and poly(gamma-glutamic acid) [gamma-PGA] molecular weight on the complex formation process. High molecular weight gamma-PGA showed a high adsorption frequency. Tn contrast, no molecular weight effect was observed in the case of chitosan. Addition of certain organic solvents in the chitosan and gamma-PGA aqueous solution also influenced ultrathin film polyion complex formation.

[160] Physical Insight in the in-Situ Self-Assembled Films of Polypyrrole

M. K. Ram, M. Adami, P. Faraci and C. Nicolini

Polymer 41(20) (2000), 7499-7509

The ultrathin films with nanometre control over thickness and multilayered structures of polypyrrole (PPY) were manufactured by in-situ self-assembled technique. A controlled thickness of PPY was deposited on polyanion, poly(styrene sulfonate) (PSS) surfaces as a function of time; previously PSS had been deposited on various substrates (glass, mica, indium-tin-oxide coated glass plates). Later, alternate PPY and PSS films were fabricated on such substrates by the layer-by-layer technique. The films were characterized by using UV-visible, electrochemical and Quartz Crystal Microbalance techniques. The resulting morphology of the manufactured films was investigated by Atomic Force and the Scanning Tunneling Microscopies. The electrochemical surveying of self-assembled PPY films in different electrolytic media highlighted the sensor application. Typical supramolecular films of PPY/PSS were found to have conductivity values in the range of 10(-2)-10(-1) S/cm. (C) 2000 Elsevier Science Ltd. All rights reserved.

[161] Polymeric Nanostructured Composite Films

J. C. Shen, J. Q. Sun and X. Zhang

Pure Appl. Chem. 72(1-2) (2000), 147-155

This research news describes the construction of polymeric nanostructured composite film based on a variety of interactions, such as hydrophobic-hydrophilic effect, electrostatic interaction, hydrogen bonding, etc. The work focused on developing strategies to solve the basic problems in the area of ultrathin film research, such as stability, improving the interface quality, creating patterned interface, and techniques to construct nanolayered structure. With in- depth study of the relationship between the microscopic layered architecture and macroscopic function of supramolecular assemblies, it is anticipated that one could obtain miniature devices or machines of high efficiency through integration of the assembling process and device fabrication.

[162] Preparation of DNA-Cationic Amphiphile Multilayer Films by Alternate Adsorption and a Study of Their Structure

L. I. Shabarchina, M. M. Montrel, G. B. Sukhorukov, I. V. Savintsev and B. I. Sukhorukov

Russian J. Phys. Chem. 74(11) (2000), 1908-1914

DNA-hexadecylamine and DNA-hexadecyltrimethylammonium bromide multilayer films were produced by alternate adsorption of DNA and a cationic amphiphile on a solid support. The growth of the film was studied by UV spectroscopy The interlayer distances, DNA conformational states, and hydration and stability of the films in aqueous and aqueous-salt solutions were determined by small-angle X-ray scattering and IR and UV spectroscopies. The structures of the films were proposed. It was shown that the DNA double helix is unwound during the formation of the hexadecylamine multilayer film. In the case of hexadecyltrimethylammonium, the DNA double helix retains the B- form, but its lability diminishes; no transition into the A- form occurs with decreasing humidity. As for hexadecylamine, the influence of the polar head of the amphiphile molecule on the DNA conformational state occurs because of the substitution of base-base intramolecular hydrogen bonds by base- hexadecylamine intermolecular hydrogen bonds. Multilayer films containing the same components but prepared under different conditions (Langmuir process or alternate adsorption of the components on the support) were found to differ in structure.

[163] Self-Assembly of Polyaniline Ultrathin Films Based on Doping- Induced Deposition Effect and Applications for Chemical Sensors

D. Li, Y. D. Jiang, Z. M. Wu, X. D. Chen and Y. R. Li

SENSOR ACTUATOR B CHEM 66(1-3) (2000), 125-127

Electroactive nanocomposite ultrathin films of polyaniline (PAN) and isopolymolybdic acid (PMA) were fabricated by a novel molecular self-assembling process based on the alternate deposition of PAN and PMA from their dilute solutions. The process was based on doping-induced deposition effect of emeraldine base. The process was monitored by UV/VIS spectroscopy measurement. It was found that the conductivity of the PAN films is sensitive to humidity, NO2 and NH3. The technique may be used to fabricate chemical sensors and other molecular devices. (C) 2000 Elsevier Science S.A. All rights reserved.

[164] Fabrication of Self-Assembled Polyaniline Films by Doping- Induced Deposition

D. Li, Y. D. Jiang, Z. M. Wu, X. D. Chen and Y. R. Li

Thin Solid Films