A thermodynamic investigation of the cellulose allomorphs: cellulose(am), cellulose I¿(cr), cellulose II(cr), and cellulose III(cr)

Published

November 11, 2014

Author(s)

Robert N. Goldberg, Jacob Schliesser, Ashutosh Mittal, Stephen R. Decker, Ana Filipa L. Santos, Vera L. Freitas, Aaron A. Urbas, Brian E. Lang, Christian Heisse, Maria D. Ribeiro da Silva, Brian F. Woodfield, Rui Katahira, Wei Wang, David K. Johnson

Abstract

The thermochemistry of samples of amorphous cellulose, cellulose I, cellulose II, and cellulose III was studied by using oxygen bomb calorimetry, solution calorimetry in which the solvent was cadoxen, and with a Physical Property Measurement System (PPMS) in zero magnetic field to measure standard massic heat capacities Cp,w over the temperature range T = (2 to 302) K. The samples used in this study were prepared so as to have different values of crystallinity indexes CI and were characterized by X-ray diffraction, by Karl Fischer moisture determination, and by using size exclusion chromatography to determine the weight average degree of polymerization DPw. NMR measurements on solutions containing the samples dissolved in cadoxen were also performed in an attempt to resolve the issue of the equivalency or non-equivalency of the nuclei in the different forms of cellulose that were dissolved in cadoxen. While large differences in the NMR spectra for the various cellulose samples in cadoxen were not observed, one cannot be absolutely certain that these cellulose samples are chemically equivalent in cadoxen. Equations were derived which allow one to adjust measured property values of cellulose samples having a mass fraction of water wH2O to a reference value of the mass fraction of water wref. The measured thermodynamic properties (standard massic enthalpy of combustion ΔcHw, standard massic enthalpy of solution ΔsolHw, and Cp,w) were used in conjunction with the measured CI values to calculate values of the changes in the standard massic enthalpies of reaction ΔrHw*, the standard massic entropies of reaction ΔrSw*, the standard massic Gibbs energies of reaction ΔrGw*, and the standard massic heat capacity Cp*,w for the interconversion reactions of the pure (CI = 100) cellulose allomorphs, i.e., cellulose(am), cellulose I(cr), cellulose II(cr), and cellulose II(cr), See manuscript for complete abstract.

Citation

Journal of Chemical Thermodynamics

Volume

81

Pub Type

Journals

Keywords

cadoxen, calorimetry, cellulose amorphous, cellulose I, cellulose II, cellulose III, enthalpy, entropy, Gibbs free energy, heat capacity, NMR

Citation

Goldberg, R. , , J. , Mittal, A. , Decker, S. , , A. , Freitas, V. , Urbas, A. , Lang, B. , , C. , D., M. , Woodfield, B. , Katahira, R. , Wang, W. and K., D. (2014), A thermodynamic investigation of the cellulose allomorphs: cellulose(am), cellulose I¿(cr), cellulose II(cr), and cellulose III(cr), Journal of Chemical Thermodynamics (Accessed December 13, 2024)