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

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 t he blending process and a base for the neutralization of acetic acid side c hain 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 melt ing 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 bl ends was analyzed by FT-IR spectra and characterized by shifting of charact eristic absorption peaks of -COO- and -NH4+. This specific interaction was due to the combination effect of the ionic and H-bonding. The X-ray diffrac tion patterns show no change of both PEO and PTAA lattice after blending. T he degradation temperatures of the blends, as measured by the thermogravime tric analysis (TGA), are higher than the pure PTAA. According to the pictur es of PTAA/PEO film taken from the optical microscopy (OM), the melting poi nt (T-m), phase equilibrium curve, and degradation temperature (T-d) of ble nd 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 o f the exposure time of the OM camera, a phase diagram (PD) can be construct ed. The conductivity of PTAA in PTAA/PEO is slightly affected by the existe nce of this specific interaction and different compositions with different morphology. (C) 2001 Elsevier Science B.V. All rights reserved.