Quantum mechanical calculations on cellulose–water interactions: structures, energetics, vibrational frequencies and NMR chemical shifts for surfaces of Iα and Iβ cellulose

• Published in: Cellulose (London) 2014-04, Vol.21 (2), p.909-926
• Main Authors: Kubicki, James D, Watts, Heath D, Zhao, Zhen, Zhong, Linghao
• Format: Article
• Language: English
• Subjects: Adsorbed water; Adsorption; Bioorganic Chemistry; Cellulose; Ceramics; Chemistry; Chemistry and Materials Science; Composites; Density functional theory; Glass; hydrogen bonding; hydrophobicity; Mathematical analysis; Natural Materials; NMR; Nuclear magnetic resonance; nuclear magnetic resonance spectroscopy; Organic Chemistry; Original Paper; Physical Chemistry; Polymer Sciences; Quantum mechanics; Surface chemistry; Sustainable Development; Vibrational spectra; Water chemistry
• ISSN: 0969-0239; 1572-882X
• DOI: 10.1007/s10570-013-0029-x

Periodic and molecular cluster density functional theory calculations were performed on the Iα (001), Iα (021), Iβ (100), and Iβ (110) surfaces of cellulose with and without explicit H₂O molecules of hydration. The energy-minimized H-bonding structures, water adsorption energies, vibrational spectra, and ¹³C NMR chemical shifts are discussed. The H-bonded structures and water adsorption energies (ΔEₐdₛ) are used to distinguish hydrophobic and hydrophilic cellulose–water interactions. O–H stretching vibrational modes are assigned for hydrated and dry cellulose surfaces. Calculations of the ¹³C NMR chemical shifts for the C4 and C6 surface atoms demonstrate that these δ¹³C4 and δ¹³C6 values can be upfield shifted from the bulk values as observed without rotation of the hydroxymethyl groups from the bulk tg conformation to the gt conformation as previously assumed.