Characterization of Cellulose Nitrate by Thin-Layer Chromatography

Abstract

ABSTRACT:The intent of this work is to establish a method for evaluating the chemical compositional distribution (CCD, in this case, nitrogen content (Ne)) and the molecular weight distribution (MWD) of cellulose nitrate (CN) using open and vapor-programed (VP) thin-layer chromatography (TLC). CCD could be determined with a nitromethane-methanol mixture in open TLC and with acetone-methanoi----{;hioroform in VP-TLC. With mainly the former, the change in the rate of flow Rt was based on the adsorption-desorption mechanism and with the latter, the separation of polymer according to Ne was interpreted by the phase separation mechanism. Both methods gave similar CCD for given CN samples. The most effective method for evaluating the weight-average molecular weight was achieved with 1,4-dioxane-methanol-isopropanol mixture in VP-TLC, for which the phase separation mechanism was operative.KEY WORDS Cellulose Nitrate / Thin-Layer Chromatography / Compositional Distribution / Molecular Weight Distribution/ AdsorptionDesorption Mechanism / Phase Separation Mechanism / Since its first appearance in 183 I, cellulose nitrate (hereafter designated as CN) has occupied, in spite of rapid growth of the production of synthetic polymers, invariably an important position in industry owing to its numerous favorable features. As is well-known, CN is commercially utilized by changing it's average molecular weight and the average degree of esterification (i.e., the nitrogen content by wt% as expressed by Ne). A number of attempts have been made to separate whole CN polymer with respect to molecular weight or Ne. But, unfortunately no effective method of compositional fractionation has yet been proposed for CN. In 1973 Kamide, et al., 1 succeeded, by using thin-layer chromatography (TLC), to evaluate molecular weight distribution (MWD) and chemical compositional distribution (CCD) of cellulose acetate. Quite recently, Kamiyama and Inagaki2 studied by TLC the compositional heterogeneity of some commercial CN samples by a concentration-gradient development using a binary acetone-ethylacetate (20/3, v/v) and another binary chloroformethylacetate (1/2, v/v) as initial and second solvents, respectively. However, they have not established a method for estimating MWD or CCD of CN by TLC technique. This work intends to fractionate CN on the basis of Ne or its molecular weight by TLC.Polymer J., Vol. 10, No. 5, 1978 EXPERIMENTAL Preparation of Polymer SamplesEleven whole samples have been used in this work. These samples were ptepared by nitrating purified cotton linter with a mixture of nitric acid and sulfuric acid, followed by a conventional thermal degradation at elevated temperatures in water. The sample W 119 was fractionated, by successive solutional fractionation (SSF) technique, into five fractions at 25°C from a 0.8-wt % solution in acetone using hexane as a precipitant. 547

Determination of Sequence Distribution of Substituted and Unsubstituted Glucopyranose Units in Water-Soluble Cellulose Acetate Chain as Revealed by Enzymatic Degradation

“…The concentration of the dissolved materials in elution was determined by a refractive index detector Shodex RI SE-61 (Showa Denko K.K., Tokyo, Japan). Each fraction was weighed by freeze-drying method and used for molecular weight measurements by high performance liquid chromatography and for structural analysis by 13 C NMR. Sample S(60)-0 (3.98 g) was dissolved to deionized water ( 10 ml), which was injected into another GPC apparatus, consisting of a glass tube (inner diameter, 25 mm; length, …”

“…In the range 60--80 ppm carbon peaks due to cello-oligosaccharide and glucose were detected. 1:F)) was estimated from the intensity ratio of acetyl methyl carbon peaks at 20 ppm to that of CA C 1 carbon peaks at 100- from analysis of carbonyl carbon region in 13 C{ 1 H} NMR spectra, according the procedure proposed previously. 2 …”

“…9 determined average molar fractions for eight kinds of unsubstituted, partially and fully substituted AHG units of cellulose acetate samples by establishing full assignments of all carbonyl peaks of 13 C{ 1 H} NMR spectra. Very recently, Buchanan et a/.…”

“…Very recently, Buchanan et a/. 10 also studied the assignment of carbonyl carbon resonances in 13 C NMR spectra of CA, prepared by acid hydrolysis of cellulose triacetate (CT A) labeled at the carbonyl carbons with carbon-13 and concluded that aqueous acid hydrolysis of labeled CT A provides for a random distribution of acetyls along the polymer backbone, while the range of DS values permits observation of nearly all of the carbonyl carbon resonances for anhydroglucose monomers.…”

“…In this article, for the purpose of evaluating the distribution of degree of substitution in incompletely substituted glucopyranose unit sequences, we used Cellulase to water-soluble cellulose acetate (CA) with known and and fractionated by liquid chromatography the degraded products and determined by 13 C NMR analysis the distribution of the degree of substitution and for each fraction separated. Also we deduced the acting mechanism of enzymatic hydrolysis of cellulosic main chains by comparing the above experimental results with computer experiments.…”