Investigation of the hydrogen-bond structure of cellulose diacetate by two-dimensional infrared correlation spectroscopy

Temperature-dependent structural changes in hydrogen bonds in cellulose diacetate (CDA) were investigated by Fourier transform infrared spectroscopy (FT-IR). The OH stretching vibration band was selected to explore the structure changes. Two-dimensional correlation spectroscopy (2DCOS) in combination with moving-window technique was applied to analyze the overlapping OH band due to various kinds of hydrogen bonds. By virtue of this powerful method, the inter-chain and intra-chain hydrogen bonds in cellulose diacetate can be identified. Moreover, typical temperature with great spectral variation was visualized by the moving-window analysis. In the temperature region of 35–100 °C, the absorbed water in the hydrogen-bond matrix broke away, and the structure of hydrogen bonds in CDA changed accordingly. When temperature increased into a higher region, both the inter-chain hydrogen bonds (comparatively strong but relatively unstable) and the intra-chain hydrogen bonds (comparatively weak but stable) began to decrease, and the inter-chain hydrogen bonds were weakened prior to the intra-chain hydrogen bonds.