Timescales technical developments

The conditions which determine whether flash photolysis can be used to smdy a given chemical system are (i) a precursor of the species of kinetic interest has to absorb light (normally from a pulsed laser) (ii) this species is produced on a timescale that is short relative to its lifetime in the system. Current technical developments make it easy to study timescales of nanoseconds for production and analysis of species, and the use of instrumentation with time resolution of picoseconds is already fairly common. In certain specific cases, as we will see in the last part of this chapter, it is possible to study processes on timescales greater than a few femtoseconds. Once the species of interest has been produced, it is necessary to use an appropriate rapid detection method. The most common technique involves transient optical absorption spectroscopy. In addition, luminescence has been frequently used to detect transients, and other methods such as time-resolved resonance Raman spectroscopy and electrical conductivity have provided valuable information in certain cases. 

Several of the examples in Table 9-1 are looking quite promising for technical realization on a short to medium timescale. Other ideas are still in their infancy, and there is still a lot of potential for the development of other new non-synthetic applications of ionic liquids in the years to come. 

Most research effort, therefore, concentrated on those polymers where it is possible to control morphology, to obtain chemically pure materials and to manipulate them to provide forms, e.g. chain oriented samples and thin films, suitable for basic research and applications. The development of synthetic routes that provide clean, reproducible samples has been critical in the progress achieved in understanding the physics of conjugated polymers. This in turn underpinned the rapid development of technological applications, which appeared on a much shorter timescale than for other, comparable technologies. The level of scientific and technical interest in polymers, such as PAc, PAni, PPy, PThs, PPVs and polyfluorenes, has resulted in the commercial production of them and their precursors. 

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