Amphiphilic, Regioregular Polythiophenes

The synthesis, characterization, and solid-state morphology of regioregular, amphiphilic polythiophenes based on 3-dodecyl-3'-(3,6,9,12-tetraoxatridecanyl)-2',5-bithiophene are described. These polythiophenes form stable monolayers on the water subphase of a Langmuir trough and are transferable (Langmuir-Blodgett deposition) to solid substrates to give highly ordered thin films. Mixing of the amphiphilic, regioregular polythiophenes with a nonconducting poly(ethylene glycol), in a 50/50 weight percent ratio, results in the formation of a semiconducting network of polythiophene in the Langmuir-Blodgett film. The solution-cast films of the amphiphilic, regioregular polythiophenes exhibit liquid-crystalline lamellar mesophases with thermotropic transitions at 0, 60, and 120 °C. These transitions are attributed to the melting of the tetraethylene glycol monomethyl ether side chains, the dodecyl side chains, and the polythiophene backbones, respectively. DSC, X-ray diffraction, and optical microscopy were used to identify the thermotropic transitions. The molecular ordering was investigated with X-ray and electron diffraction. Potentially, the regioregular, amphiphilic polythiophenes are applicable as efficient material in field-effect transistors.