Luminescence of poly(3-thiopheneacetic acid) in alcohols and aqueous solutions of poly(vinyl alcohol)

Stable aqueous solutions of poly(3-thiopheneacetic acid) (PTAA), including its acid form, were suitably prepared by using poly(vinyl alcohol) (PVA) as steric stabilizer surfactant. The optical properties of PTAA were investigated in aqueous solution of PVA, water and different alcohols. Both absorption and emission measurements revealed that the optical behavior of PTAA is pH-dependent. The maximum of absorption of PTAA salt in PVA solution shifts from 480 to 415 nm when acid conditions are established, producing a color change from brown-red to yellow. The same solvatochromic effect was also verified from the emission spectra, being the band shift attributed to conformational changes of the PTAA structure due to formation or dissociation of hydrogen bonds between carboxyl groups of PTAA and hydroxyl groups of PVA. In a similar way, the impact of solvents such as water, ethanol and ethylene glycol was also studied on both absorption and emission spectra of PTAA.