FTIR assessment of poly(ethylene oxide) irradiated in solid state, melt and aqeuous solution

FTIR spectroscopy was used to study poly(ethylene oxide), PEO, irradiated in solid and molten aggregate states and as aqueous solutions of various concentrations. The changes in shape and width of –C–O–C– complex absorption intensities at around 1112 cm−1 were the most prominent. On irradiation of solid samples in contact with air shrinking of –C–O–C– complex and increase in its absorption intensities indicated predominant degradation. Crosslinking prevailed on irradiation of molten PEO and of its aqueous solutions in nitrogen atmosphere and manifested itself as widening of –C–O–C– absorption and decrease of corresponding intensities. Partial or complete merging of CH2 wagging vibrations at 1342 cm−1 and 1360 cm−1 that are characteristic of crystalline PEO into a single absorption at around 1350 cm−1 indicated amorphization what was observed for samples that had reduced degree of crystallinity determined by differential scanning calorimetry. DSC could not discriminate between degradation and crosslinking while the changes in width and shape of –C–O–C– complex were independent of the changes in crystallinity. Comparison of FTIR spectra of the same PEO samples obtained as thin film and as KBr pellets revealed that pellet preparation results in a number of spectral artefacts.

► PEO irradiated in various aggregate states, in air or nitrogen was studied by FTIR spectroscopy.
► Discrimination of spectral changes due to degradation and crosslinking is attempted.
► Shape and intensities of –C–O–C– absorption peaks indicated degradation or crosslinking.
► Degree of crystallinity monitored through changes in CH2 absorptions at 1360 cm−1 and 1342 cm−1.
► Pressing into KBr pellets induces artefacts in FTIR spectra of PEO.