Titration behaviors and spectral properties of hydrophobically modified water-soluble polythiophenes

The poly(3-thiopheneacetic acid) copolymers with 3-n-methylthiophene or wit h a 3-n-octadecylthiophene at the 3-position of a thiophene ring were synth esized. The solution and spectral properties of these hydrophobically modif ied polythiophenes have been studied by potentiometric titration. UV-visibl e spectroscopy. The effects of the rigid conjugated main chain, the steric hindrance and the hydrophobicity of a long alkyl side chain on the backbone conformational change have been discussed. We found that the conformationa l transition from the aggregate state to the extended state of the hydropho bically modified polythiophenes by the change of pH is sensitively restrict ed by the introduction of the hydrophobic alkyl or long alkyl side chains. (C) 2001 Elsevier Science Ltd. All rights reserved.