1 Institute of Solid State Physics , Graz University of Technology , Petersgasse 16 , 8010 Graz , Austria.
2 Institute for Pharmaceutical Sciences, Department of Pharmaceutical Technology , Karl-Franzens University of Graz , 8010 Graz , Austria.
3 Department of Physics, Department of Chemistry and Biochemistry , Concordia University , H4B 1R6 Montréal , Canada.
4 Department of Bioproducts and Biosystems , Aalto University , P.O. Box 16300, 00076 Aalto , Finland.
5 Institute of Paper, Pulp and Fiber Technology , Graz University of Technology , 8010 Graz , Austria.

Structural Order in Cellulose Thin Films Prepared from a Trimethylsilyl Precursor.

Biomacromolecules. 2019 Dec 12;:

Authors: Jones AOF, Resel R, Schrode B, Machado-Charry E, Röthel C, Kunert B, Salzmann I, Kontturi E, Reishofer D, Spirk S

Abstract

Biopolymer cellulose is investigated in terms of the crystallographic order within thin films. The films were prepared by spin-coating of a trimethylsilyl cellulose precursor followed by an exposure to HCl vapors; two different source materials were used. Careful precharacterization of the films was performed by infrared spectroscopy and atomic force microscopy. Subsequently, the films were investigated by grazing incidence X-ray diffraction using synchrotron radiation. The results showed broad diffraction peaks, indicating a rather short correlation length of the molecular packing in the range of a few nanometers. The analysis of the diffraction patterns was based on the known structures of crystalline cellulose, as the observed peak pattern was comparable to cellulose phase II and phase III. The dominant fraction of the film is formed by two different types of layers, which are oriented parallel to the substrate surface. The stacking of the layers results in a one-dimensional crystallographic order with a defined interlayer distance of either 7.3 or 4.2 Å. As a consequence, two different preferred orientations of the polymer chains are observed. In both cases, polymer chain axes are aligned parallel to the substrate surface, and the orientation of the cellulose molecules are concluded to be either edge-on or flat-on. A minor fraction of the cellulose molecules form nanocrystals that are randomly distributed within the films. In this case, the molecular packing density was found to be smaller in comparison to the known crystalline phases of cellulose.

PMID: 31774663 [PubMed - as supplied by publisher]