Cellulose Esters and Ethers

Abstract

Cellulose esters and ethers are widely used in the production of films, plastics, artificial fibers, powder explosives, etc. It is not surprising that the first papers on the infrared spectrum of cellulose were concerned with these compounds. In a 1933 publication, Orlova and Fedorov [45] reported their work on the spectra of celluloid and benzyl- and ethylcelluloses directed to finding a substitute for normal industrial glasses. This investigation, like that of Wells [152], who considered the transparency to infrared radiation of ethylcellulose and acetylcellulose, are now only of historic interest. Nikitin [46] investigated the process of dissolution of dinitrocellulose and acetylcellulose in an ether—alcohol mixture of acetone, dioxan, pyridine, and acetic acid. He found that, in the dissolution process, the band of the unsubstituted hydroxyl groups in the esters broadened and shifted to a longer wavelength. On this basis he concluded that dissolution of the cellulose esters was molecular in nature. The spectrum of trimethylcellulose was investigated by Stelle and Pacsu [153]. Brown, Holiday, and Trotter [154] studied the infrared spectra of cyanoethylcellulose, ethylcellulose, acetylcellulose, acetobutyrylcellulose, etc., in the regions of the main frequencies of OH and CH groups. The spectra of a large number of cellulose esters and ethers between 2 and 15 μ were given by Kuhn, mainly for identification purposes [124]. Infrared spectroscopy has been used to investigate the characteristics of a number of cellulose esters, obtained from woods of various ages [33–35]. Gerbaux [155] used analysis of the symmetry of hydroxyl bands in the infrared absorption spectrum for determining specific features of hydrogen bonding in cellulose acetates, obtained by homogeneous and heterogeneous methods. Spectra of a large number of cellulose esters were obtained in the work of O’Connor and his co-workers [112, 114]. Bouriot [156] investigated the polarization spectra of cellulose acetates with various degrees of acetylation. The infrared spectra of cellulose fibers, with different degrees of acetylation—from the triacetate to the almost completely hydrolyzed product — have been studied in the region 400–3600 cm−1 [25]. A spectroscopic investigation of ethylcellulose, with an emphasis on infrared spectroscopy, was carried out by Katibnikov, Ermolenko, and others [47]. Hurtubise [157] attempted the quantitative determination of acetyl groups in acetylcellulose, and interpreted some of the main frequencies. Infrared spectroscopy was used by Kurlyankina, Polyak, and Koz’mina [48] to investigate the thermal oxidation of cellulose esters.