Poly electrically active polymers

Pitha and co-wodcers (43) have been able to demonstrate in a series of studies the poly(vinyl uracil) [10] and polyfvinyladenin) [22] to show in fact antiviral activity, but probably no interferon induction. Rather, it has been shown, that these electrically neutral polymers with a molecular weight... 

This device employs single-stranded poly(adenylic acid) [poly(A)] as the chemical recognition agent. This species selectively recognizes its complementary polymer, poly(U), through hybridization to form a double-stranded nucleic acid. The poly(A) is immobilized onto the activated surface of a quartz piezoelectric crystal, which is a mass-sensitive transducer. Electric dipoles are generated in anisotropic materials (such as quartz crystals) subjected to mechanical stress, and these materials will... 

Fig. 2.11. Three organic semiconducting polymers, (a) Polypyrrole, (b) plythipo-hene, and (c) poly(3,4-ethylenedioxythiophene) (PEDOT). All three have an sp conjugated backbone identical to polyacetylene. It is along the pi-bonds in this backbone that these materials exhibit carrier delocalization and electrical activity.

It was also observed that conjugated polymers that are also electrical conductors (see Chap. 10) exhibit optical activity that depends critically on their structural organization [78]. Thus, strong chiroptical properties can be obtained firom substituted polythiophene [79] (Chap. 10) with optically active side chains, especially when the monomers are coupled within the polymer in a regioregular head-to-tail fashion. Actually, optical activity of these materials is only found when the polymers are aggregated at low temperature, in poor solvent, or in solution cast films. This contrasts with other optically active polymers, like polypeptides, poly(l-alkynes) and polyisocyanates that show an optically active conformation of the main chain in the absence of supramolecular association. 

Most of the reported conjugated polymers with nonlinear optical or electrical activities are carbon-carbon conjugated systems, such as the extensively studied polyenes (e.g., polyacetylenes [15], polydiacetylenes [16,17], poly-/ -phenylenes) and heteroaromatic polymers (e.g., polypyrroles, polythiophenes, polycarbazoles, polyanilines) [18]. The synthetic methods, applications, and the structure-property relationships of these polymers have also been substantially investigated [19-21]. 

K. H. Hall, Jr., R. J. Chou, J. CMcu. O. R. Hughes, J. Schctiibeun, and B. Newman, Piezo-electric activity in films of poly(l-bicyclob tanccsiboajlTik), Polymer Bull 77 135 (1987). 

Side-chain substitutions are now routinely used to enhance solvent solubility and fusibility so that various conventional polymer processing methods may be used. Some of these polymeric materials, e.g., the poly(3-al-kylthiophenes), may contain only a small volume fraction of electrically active regions (i.e., the 7r-conjugated main chain). Still these materials can exhibit extremely high dc conductivities (7) after doping (or more precisely, intercalation) by a guest species. This intercala-... 

Multiple Heck reactions have also been applied in a number of ways to prepare polymers (Scheme 40). One-dimensionally 7r-conjugated polymers are attractive materials because of their optical and electrical properties resulting from 7r-electron delocalization along their main chains. Among these, poly(p-phenylenevinylene) (PPV) shows high electrical conductivity, large non-linear optical responses, and electroluminescent activity. One approach... 

The anode layer of polymer electrolyte membrane fuel cells typically includes a catalyst and a binder, often a dispersion of poly(tetraflu-oroethylene) or other hydrophobic polymers, and may also include a filler, e.g., acetylene black carbon. Anode layers may also contain a mixture of a catalyst, ionomer and binder. The presence of a ionomer in the catalyst layer effectively increases the electrochemically active surface area of the catalyst, which requires a ionically conductive pathway to the cathode catalyst to generate electric current (16). 

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