Other Conjugated Polymers

The versatility of poly(phenylcne) chemistry can also be seen in that it constitutes a platform for the design of other conjugated polymers with aromatic building blocks. Thus, one can proceed from 1,4- to 1,3-, and 1,2-phenylene compounds, and the benzene block can also be replaced by other aromatic cores such as naphthalene or anthracene, helerocyclcs such as thiophene or pyridine as well as by their substituted or bridged derivatives. Conceptually, poly(pheny ene)s can also be regarded as the parent structure of a series of related polymers which arc obtained not by linking the phenylene units directly, but by incorporation of other conjugated, e.g. olefinic or acetylenic, moieties. 

At this point it might be appropriate to comment on the conflicting requirements of the synthesis. The large interest which other conjugated polymers such as polypyrrole, polyanilinc or poly(parattracted originates, firstly, from their attractive physical properties, but also from the sim-... 

The excellent agreement between the TSC and P1A results has two implications. First, since the TSC method probes the product of mobility and carrier density, while the P1A probes only the carrier density, there seems to be no dominant influence of temperature on the carrier mobility. This was also found in other conjugated polymers like /ra/ry-polyacetylene [19, 36]. Second, photoconductivity (observed via the thermal release of photoexcited and trapped earners) and photo-induced absorption probe the same charged entity [36, 37J. 

Just as with other conjugated polymers, the emission color of PPE can be tuned by introducing different conjugated fragments in the polymer chain (copolymers 523 and 524) [627,638], Thus, red-orange EL (AEL 590 nm and a shoulder at 530 nm) was reported for the anthracene-based polymer 523 (in PLED ITO/523/A1), whereas... 

Organic molecules having many degenerate orbitals 187 Poly(m-phenylenecarbenes) 194 Poly(acetylenes) and other conjugated polymers 197 Analytical methods and characterization 201 Epr fine structure 201... 

Polyacetylene is very susceptible to attack by oxygen. The polymer loses its metallic lustre and becomes brittle when exposed to air. However, other conjugated polymers were found. Polypyrrole, polythiophene, polyaniline, polyphenylenevinylene (Figure 6.4), and others are conjugated polymers whose bonding and con-... 

Most photoeonductive polymers can be used in solar batteries. The high resistivity of the polymers decreases the actual power of the devices. Possibilities may be connected with electron-donor doping of the polymers. As stated earlier some success has been achieved in this field for polyacetylenes and other conjugated polymers. 

Two natural extensions of this work are currently in progress first, it, is possible, in some extents, to improve the simple ansatz (26) by including more local configurations [42] second, it is also possible to apply the method to other conjugated polymers of current interests as the poly-paraphenylene and the poly-paraphenylenevinylene. 

Although the original research on conductive polymers was done with polyacetylene, a number of other conjugated polymers have been developed for such uses. Among these products are the polythiophenes, polyanilines, polyphenylenevinylenes, polyethylene-dioxythiophenes, polypyrroles, and polydialkylfluorenes. These products are now beginning to find applications in a number of industrial, research, medical, and consumer devices. 

In these doping processes, not only of polyacetylene but also of other conjugated polymers, the introduced counter dopant ions stabilise the charge on the polymer backbone. There are doping processes, however, where no counter ions are involved. Examples are photo doping and charge injection doping. 

The first conducting polymer was trans-polyacetylene which was doped with bromine and was produced at 1970s. Soon other conjugated polymers such as poly (p-phenylene), polypyrrole (PPy), polyethylene dioxythiophene (PEDOT) and polyaniline (PANi) and their derivatives which are stable and processable were synthesized. The molecular structures of a few ICPs are shown in Figurel. 

Fig. 9.20, where R has a maximum value of 0.66. This effect accounts for the metallic appearance of PAc and other conjugated polymers. 

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