Solution processable alternating oligothiophene-PEO-block-co-polymers: synthesis and evidence for solvent dependent aggregation

A new route to oligothiophene-PEO-block-co-polymers has been developed, in which well-defined alpha-oligothiophene blocks (from bithiophene to sexithiophene) alternate with poly(ethylene oxide) blocks. These materials show high solubility in common organic solvents. UV/visible and fluorescence studies in solution indicate that the oligothiophene segments are molecularly dissolved in good solvents like chloroform. Aggregation of the oligothiophenes occurs in dioxane-water mixtures, which is manifest by shifts of the UV/visible absorption maxima towards the blue and quenching of the fluorescence. An oligothiophene length of three thiophenes (terthiophene) is necessary to observe this aggregation phenomenon.