Miscibility of poly(thiophene-3-acetic acid) and poly(ethylene oxide)

Abstract

Poly(thiophene-3-acetic acid) (PTAA), prepared from polymerization of ethyl-thiophene-3-acetate followed by hydrolysis, was blended with poly(ethylene oxide) (PEO). The 1.5% aqueous ammonia solution was used as a solvent in the blending process and a base for the neutralization of acetic acid side chain of PTAA, which also results in the dissolution of PTAA in the solvent. Thermal analysis by DSC thermograms of PTAA/PEO blends shows that the melting points of PTAA/PEO blends are slightly lower than that of the neat PEO when re-crystallized from molten state. This specific interaction of the blends was analyzed by FT-IR spectra and characterized by shifting of characteristic absorption peaks of COO − and NH 4 +. This specific interaction was due to the combination effect of the ionic and H-bonding. The X-ray diffraction patterns show no change of both PEO and PTAA lattice after blending. The degradation temperatures of the blends, as measured by the thermogravimetric analysis (TGA), are higher than the pure PTAA. According to the pictures of PTAA/PEO film taken from the optical microscopy (OM), the melting point ( T m), phase equilibrium curve, and degradation temperature ( T d) of blend samples can be roughly measured. Combined the T m obtained from the DSC data and the cloud point defined as the temperature when a sharp increase of the exposure time of the OM camera, a phase diagram (PD) can be constructed. The conductivity of PTAA in PTAA/PEO is slightly affected by the existence of this specific interaction and different compositions with different morphology.