Conjugated solid state properties

The electrical conductivity of a material is a macroscopic solid-state property since even in high molecular-weight polymers there is not just one conjugated chain which spans the distance between two electrodes. Then it is not valid to describe the conductivity by the electronic structure of a single chain only, because intra- and interchain charge transport are important. As with crystalline materials, some basic features of the microscopic charge-transport mechanism can be inferred from conductivity measurements [83]. The specific conductivity a can be measured as the resistance R of a piece of material with length d and cross section F within a closed electrical circuit,... 

The most important structural features of amorphous SAN copolymers are the weight fraction (h an) of acrylonitrile and the molecular weight distribution (MWD). These features control the solid-state properties and fabrication performance. Also important are the type and level of conjugated chromopores and the monomer sequence distribution. These features control the visual appearance of the SAN copolymer. The chromophores may introduce unwanted yellowness. A nonuniform sequence distribution may cause unwanted haze from phase separation. 

After covering the interplay of the excited state with chemical and structural defects, we will now consider how changes in the chemical structure affect the properties of conjugated polymers, in particular the focus will be put on PPP-type structures with increasing degree of bridging. In the following, the most important issues related to both the chemical structure and the solid state properties... 

Since in most applications conjugated materials are used in the solid form, an important advantage of oligomers is therefore that the solid state properties can be investigated in crystals or in vapor-deposited (thin) films. However, in the solid state morphological and supramolecular effects may play an important role and lead to different properties than those found in solution. 

Gas Phase to Solid State Evolution of the Electronic and Optical Properties of Conjugated Chains A Theoretical Investigation... 

The transfer of PCSs from solutions into the solid state may be accompanied by the origination of hydrogen and salt bonds, by associations in crystalline regions, or by charge transfer states and some other phenomena. These effects are followed by some conformational transformations in the macromolecules. The solution of the problem of the influence of these phenomena on the conjugation efficiency and on the complex of properties of the polymer is of fundamental importance. 

An important challenge in the design of novel conjugated polymers is the synthesis of materials with tailor-made solid-state electronic properties. This section outlines the synthesis of the most significant classes of poly(para-phenylenevinylene)s (PPVs), poly(para-phenylene)s (PPPs), and related structures. Furthermore, this review demonstrates that the chromophoric and electronic properties of conjugated rr-systems are sensitive to their molecular and supra-molecular architecture. 

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