Polythiophenes, properties switching

Mechanical Properties of Polythiophenes Chemical properties Switching properties Optical properties of polythiophenes... 

Polythiophenes (PTs) have received a great deal of attention due to their electrical properties, environmental stability in doped and undoped states, non-linear optical properties, and highly reversible redox switching [1]. Thiophene possesses a rich synthetic flexibility, allowing for the use of several polymerization methods and the incorporation of various side chain functionalities. Thus, it is of no great surprise that PTs have become the most widely studied of all conjugated polyheterocycles [184]. 

Polythiophenes are normally produced from nonaqueous media because the monomer is more soluble in these. Also, a wider electrochemical potential window is available, and this is required as polythiophene is more difficult to oxidize than pyrrole. The influence of water on the polymerization process for thiophene and on the redox switching properties has been studied.1314 The presence of water as low as... 

Another interesting application that uses the dynamic properties of conducting polymers is electrochromic devices. - For example, polythiophene and polyaniline undergo distinct color changes when an electrical potential is applied. Thin films of polythiophene can be switched from red (oxidized)... 

Polythiophenes are normally produced from nonaqueous media since the monomer is more soluble in these. Also, a wider electrochemical potential window is available and this is required since polythiophene is more difficult to oxidize than pyrrole. The influence of water on the polymerization process for thiophene and on the redox switching properties has been studied. - The presence of water as low as 1% causes mislinkages and a subsequent deterioration in polymer properties. Other authors have claimed that optimal polymers are produced from propylene carbonate solvent. These same workers also point out that the minimum thiophene concentration required to enable pol5merization is solvent dependent. The required minimal monomer concentration decreases for solvents with a large dielectric constant. They claim that solvents with a high dielectric constant (having an electron-with-drawing substituent) influence the reactivity of the cation radical intermediate and, therefore, play an important role in the polymerization process. 

Even with PPys or polythiophenes the presence of other functional groups on the 3 or 4 position can be used to adjust the chemical properties and the electrochemical switching properties. For example the addition of alkyl groups results in polymers that are more hydrophobic (9) and also more soluble in common organic solvents. We have also shown that the addition of carboxy groups introduces self doping to the polymer and therefore cation exchange properties (10,11). 

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