Polymer films devices

Polymers. The Tt-conjugated polymers used in semiconducting appHcations are usually insulating, with semiconducting or metallic properties induced by doping (see Flectrically conductive polymers). Most of the polymers of this type can be prepared by standard methods. The increasing use of polymers in devices in the last decade has led to a great deal of study to improve the processabiUty of thin films of commonly used polymers. 

The apphcation of a high electric field across a thin conjugated polymer film has shown the materials to be electroluminescent (216—218). Until recentiy the development of electroluminescent displays has been confined to the use of inorganic semiconductors and a limited number of small molecule dyes as the emitter materials. Expansion to the broad array of conjugated polymers available gives advantages in control of emission frequency (color) and facihty in device fabrication as a result of the ease of processibiUty of soluble polymers (see Chromogenic materials,electrochromic). 

By 1988, a number of devices such as a MOSFET transistor had been developed by the use of poly(acetylene) (Burroughes et al. 1988), but further advances in the following decade led to field-effect transistors and, most notably, to the exploitation of electroluminescence in polymer devices, mentioned in Friend s 1994 survey but much more fully described in a later, particularly clear paper (Friend et al. 1999). The polymeric light-emitting diodes (LEDs) described here consist in essence of a polymer film between two electrodes, one of them transparent, with careful control of the interfaces between polymer and electrodes (which are coated with appropriate films). PPV is the polymer of choice. 

Polymer LEDs are similar to thin film organic molecular LEDs first reported in 1987 17). Organic molecular LEDs utilize thin films of small organic molecules rather than polymer films as the light-emitting layer. The films of small organic molecules are undoped and have electronic properties comparable to the polymer films used in polymer LEDs. In general, the device physics of polymer LEDs is... 

Several narcotic antagonists, including naloxone, naltrexone, L-methadone, and cyclazocine, have been incorporated in lactide homopolymers and lactide/glycolide copolymers. Cyclozocine was incorporated in poly(L-lactide) in the form of films (81,82). Lamination of drug-polymer films with a drug-free film created a reservoir device and eliminated the burst observed with the monolithic films originally tested. 

We have shown a new concept for selective chemical sensing based on composite core/shell polymer/silica colloidal crystal films. The vapor response selectivity is provided via the multivariate spectral analysis of the fundamental diffraction peak from the colloidal crystal film. Of course, as with any other analytical device, care should be taken not to irreversibly poison this sensor. For example, a prolonged exposure to high concentrations of nonpolar vapors will likely to irreversibly destroy the composite colloidal crystal film. Nevertheless, sensor materials based on the colloidal crystal films promise to have an improved long-term stability over the sensor materials based on organic colorimetric reagents incorporated into polymer films due to the elimination of photobleaching effects. In the experiments... 

Hydrophobic polymer materials that slowly release N O can be used on the surface of medical devices. Many medical devices suffer from the surface adhesion of blood platelets. To minimize this thrombogenic effect, blood thinners such as heparin, coumarin, and aspirin are often used. However, systemic administration of antiplatelet agents could increase the risk of uncontrolled bleeding elsewhere in the body. In contrast, biocompatible polymer films would solve this problem [153]. It is possible to create polymeric surfaces that mimic the inner surface of a blood vessel by... 

M. Granstrom, M. Berggren, D. Pede, O. Inganas, M.R. Andersson, T. Hjertberg, and O. Wennerstrom, Self-organizing polymer films — a route to novel electronic devices based on conjugated polymers, Supramol. Sci., 4 27-34, 1997. 

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