Clear evidence of the sensitivity of the solvatochromic effect to side chain functionalization in 3-hexyl-substituted polythiophenes

The solvatochromic properties of 3-hexyl-substituted polythiophenes functionalized with an ester, ether or hydroxy group at the end of the alkyl side chain are reported. An extraordinarily large shift, Delta lambda(max) = 99 nm, and a dramatic change of the UV/vis spectral profile are found when the carboxylate is replaced with the hydroxy group by functionalization exchange. The solvatochromic behavior of each polymer is believed to be strictly related to the type of functional group owing to different physical interactions (solvation) between groups different in polarity and solvent molecules. A unique and common chromophoric unit for the final conformation of the 3-hexyl-substituted polythiophenes, induced by the solvatochromic effect, is also suggested.