13C NMR determination of the distribution of two ester substituents in cellulose acetate butyrate

✍ Scribed by Yasuyuki Tezuka

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 331 KB
• Volume: 241
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(93)80117-w

✦ Synopsis

A cellulose ester derivative having two different substituents, namely, cellulose acetate butanoate (butyrate) (CAB) has been produced commercially for a wide variety of applications, such as molding plastics, film products, lacquer coatings, and melt coatings'. As the final properties of these products may be optimized through precise control of the distribution pattern of the two ester substituent groups on a glucose residue ("anhydroglucose unit") in addition to control of the relative and the total contents of the two substituents, a simple and reliable analytical method is of a significant importance both for elucidating structureproperty relationships and for achieving quality control in production process.

We have recently proposed2-7 a new analytical technique for cellulose derivatives, in particular cellulose ethers, in which unsubstituted hydroxyl groups on the anhydroglucose unit (and those at the end of substituent groups in some cases) are peracetylated and subjected to NMR measurements. We have demonstrated that the acetyl and other ester carbonyl carbon signals may be utilized as an extremely sensitive NMR probe for monitoring the substitution position on the anhydroglucase unit. Extending the preceding studies, we herein report a 13C NMR determination of the distribution of acetyl and butanoyl (butyryl) substituents in commercial CAB samples.

A full-range 13C NMR spectrum of a CAB sample is shown in Fig. 1. In addition to the signals for C-l-C-6 in the anhydroglucose unit, the methyl (doublet at 13.5 and 13.6 ppm) and methylene (doublet at 18.0 and 18.3 ppm, and doublet at 35.7 and 35.9 ppm) signals from the butyryl groups and the acetyl methyl signal (doublet at 20.4 and 20.6 ppm) were observed, and the relative contents of the two