Temperature-dependent changes in hydrogen bonds in cellulose Ialpha studied by infrared spectroscopy in combination with perturbation-correlation moving-window two-dimensional correlation spectroscopy: comparison with cellulose Ibeta.

Our recent IR study demonstrated that hydrogen-bond structure in cellulose Ibeta drastically changes around 220 degrees C (Watanabe et al. Biomacromolecules 2006, 7, 3164). In the present study, temperature-dependent IR spectra of cellulose Ialpha from 30 to 260 degrees C were analyzed by use of perturbation-correlation moving-window two-dimensional correlation spectroscopy. It was observed that as in the case of cellulose Ibeta abrupt changes in the hydrogen-bond structure occur around 220 degrees C in cellulose Ialpha. It was also revealed that although weakly hydrogen-bonded OH groups in Ibeta are stable below 230 degrees C thermal oxidation of those in Ialpha is accelerated around 220 degrees C. In this way, the present study has clarified a difference between the thermal behavior of Ialpha and that of Ibeta at the functional group level. Our result suggests that the drastic change in the hydrogen-bond structure around 220 degrees C makes cellulose Ialpha much more unstable than Ibeta.