Conjugated polymers electrical conductivity

Table 2 shows the present state-of-the-art for the electrical conductivity of doped conjugated polymers. The magnitude of the electrical conductivity in polymers is a complex property determined by many stmctural aspects of the system. These include main-chain stmcture and TT-ovedap, molecular... 

Balabanov, E. I., A. A. Berlin, V. P. Parini, V. L. Tal Roze, E. L. Franke-vich, and M. I. Cherkashina Electrical conductivity of polymers with conjugated double bonds. Dokl. Akad. Nauk. 134, 1123 (1960). 

Conjugated Polythiophenes. Because of their potential electrical conductivity, conjugated polythiophenes, along with other conjugated polymeric systems, have been extensively studied since the pioneering works in the early 1980s (65,66) (see Electrically conductive polymers). 

Substantial efforts have been made to produce electrical conducting conjugated rigid-rod polymers, including PBZT, PBZO, and their derivatives. PBZT fibers spim from nickel phthalocyanine solutions and followed by chemical... 

It is well known that the electrical conductivity of polymers is related to the concentration of conjugated double bonds [73]. It has been shown that the irradiation of PE with 40 keV Ar ions produces conjugated double bonds, the concentration and conjugation length of which is an increasing function of the ion fluence. The electrical sheet resistance, R, decreases, probably due to progressive carbonization of the PE surface [73]. 

Several factors can affect electrical conductivity in polymers. These factors include the extent of conjugation and regioregularity of the polymer, its molecular weight, and the interchain distance (29). Processing variables, such as temperature and pH, are also important (33). These factors will be discussed below using polypyrrole and 3-undecylbithiophene as examples. 

The answer to the question of whether an interchain or intrachain process is the dominant one responsible for electrical conductivity in conjugated polymers comes from the study of the electrical conductivity of polymers as a function of molecular weight. 

In recent years a vast amount of research has been devoted to the study of electrically conducting organic polymers(7,2). Applications for these materials include batteries, solar cells, electromagnetic shielding, sensors and "smart" windows, in addition to a myriad of other potential uses. Synthesis of conducting polymers can be achieved electrochemically (3,4) or catalytically (5). The basic concept in each case is to produce a conjugated polymer system which has been "doped" by exposure to an appropriate oxidising or... 

Finally, a quite new series of comb polymers has been reported (Fig. 7.33) that are both mesomorphic (biphenyl aryl ester side chains) and, after doping, electrically conductive (conjugated main chain). The polymers are made by heating complexes formed between the corresponding nitrile (R—CN) and a transition-metal halide, and the process can be carried out at a mesophase temperature to allow ordered polymerization. The relationships between micro- and/or macroscopic ordering and electrical conductivity have yet to be established, but fascinating thermoelectrical applications can be envisaged. 

Generally speaking, electrically conductive polymers are composed of conjugated polymer chains with TT-electrons delocalized along the backbone. 

Recently, polyimines include the synthesis of long alkoxy (Cg-Cig) side chain derivatives [188,189], which are presumably soluble to some extent in organic solvents and derivatives containing fluorene cardo unit [190]. Trifluoromethyl groups [191] in the polymer backbone provide solubility in organic solvents. Studies of the electrical conductivity of doped conjugated aromatic polyimines and alkoxy derivatives have been reported [188], and the values are in the range of 10 to 10 S/ cm. 

The electrical conductivity in the solid state is determined by the product of the carrier concentration and the carrier mobility. In conjugated polymers both entities are material dependent and, i.e., are different for electrons and holes. Electrons or holes placed on a conjugated polymer lead to a relaxation of the surrounding lattice, forming so-called polarons which can be positive or negative. Therefore, the conductivity, o, is the sum of both the conductivity of positive (P+) and negative polarons (P ) ... 

Preliminary measurements of electrical conductivity of the conjugated derivatives of PBTAB, PBTB and PTTB obtained by the above treatment with bromine vapor are poor semiconductors with a conductivity of the order 10 °S/cm which apparently is not due to doping. Subsequent electrochemical or chemical doping of these polymers lead to 4-6 orders of magnitude increase in conductivity. Ongoing studies of the electrical properties of these conjugated polymers with alternating aromatic/quinonoid units will be reported elsewhere. 

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