Polycondensation Reaction of Bis(Hydroxyethylterephthalate)—Self Modeling Curve Resolution Analysis of On-Line ATR/FT-IR Spectra

This study presents a thorough qualitative-quantitative analysis by self-modeling curve resolution (SMCR) methods of ATR/FT-IR spectra of the polycondensation reaction of bis(hydroxyethylterephthalate) (BHET) that yields poly(ethyleneterephthalate) (PET) as a final product. We used five different SMCR methods to extract pure-component spectra and concentration profiles. All the results obtained by these five methods are compared. It is shown that particular attention should be given to the scaling of the data. The spectral profiles of the species are obtained through the pure variables determined. Because of the appearance of negative absorbances, the spectra are subjected to the alternating least-square procedure. Rank analysis of the mean centered data shows that the IR spectra of the system in the reaction vessel are predominantly determined by those of BHET and PET, but that a small amount of ethylene glycol (EG), which was evacuated from the reaction vessel, also contributes to the spectra.