Variable temperature FTIR study of poly(ethylene-co-vinyl alcohol)-graft-poly(epsilon-caprolactone)

A recently developed technique, i.e., two-dimensional infrared (2D IR) correlation spectroscopy, is used to study the thermal behavior of poly(ethylene-co-vinyl alcohol)-graft-poly(epsilon-caprolactone), a new synthesized highly grafted copolymer. The use of the 2D IR approach to analyze temperature-dependent spectra collected in situ during the temperature elevation process effectively enhanced the spectral resolution and revealed details on the hydrogen bonding and conformational change which are not easily detected in the traditional one-dimensional spectra. The sequence of the spectral changes of different OH and CH(2) fundamental vibrations during heating the polymer was inferred from the signs of the asynchronous peaks. Evidence that the conformational changes of the methylene groups precede the loosening of hydrogen bonds is provided.