Conjugated interchain interactions

The introduction of bulky side chains that contain adamantyl groups to poly(p-phenylenevinylene) (PPV), a semiconducting conjugated polymer, decreases the number of interchain interactions. This action will reduce the aggregation quenching and polymer photoluminescence properties would be improved [93]. 

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The conjugated polymer diluted by a proper host matrix shows less interchain interaction than pure films. 

However, in all these calculations, the conjugated chains bear H atoms only. As bulkier side groups are introduced, the overall interchain interaction decreases and it becomes more anisotropic. If chains form stacks, relatively strong two-dimensional coupling will persist and may still have consequences similar to those of three-dimensional coupling. The question remains open. But substituted CPs are generally even more disordered than the simple ones, and we shall see now that disorder will then have more important consequences than the details of interchain interaction. 

In fact, in most cases the conjugation is not limited by the chain length, but by disorder along it, and the physical properties are also governed by interchain interactions (see Chapter 11). Determination of the structure of the actual samples studied, and possibly its modification to change (improve) the physical properties, are therefore important and are discussed in Section II. Electronic properties are then considered in Sections III (optical properties) and IV (conductivity in the undoped state). All that information is then used to present a few selected potential applications in Section V. 

These segregated side groups will either shield conjugated chains from one another, or induce a partial two-dimensional ordering of CP chains (i.e., an incipient lamellar structure). In all cases, interchain interactions will be affected. Substitutions have therefore also been attempted to modulate and control interchain interactions and therefore electrical conductivity [66]. 

An often harmful effect in conjugated polymers is aggregation via locally enhanced interchain interaction. It depresses the excited-state energy in the dimer/aggregate. If the oscillator strength of the lowest transition is lower than average this causes a prolongation of the fluorescence lifetime and, since nonra-diative channels are not affected, a decrease of the fluorescence efficiency that is detrimental for OLEDs. 

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