Cellulose ester long-chain

Schemes are available, however, that start from the free carboxylic acid, plus an activator . Dicyclohexylcarbodiimide, DCC, has been extensively employed as a promoter in esterification reactions, and in protein chemistry for peptide bond formation [187]. Although the reagent is toxic, and a stoichiometric concentration or more is necessary, this procedure is very useful, especially when a new derivative is targeted. The reaction usually proceeds at room temperature, is not subject to steric hindrance, and the conditions are mild, so that several types of functional groups can be employed, including acid-sensitive unsaturated acyl groups. In combination with 4-pyrrolidinonepyridine, this reagent has been employed for the preparation of long-chain fatty esters of cellulose from carboxylic acids, as depicted in Fig. 5 [166,185,188] ...

Introduction. Today nitrocellulose is one of most important derivatives of cellulose used in industry and commerce, and a major product of the chemical industry. Its wide and manifold applications are due mainly to its extraordinary physical properties. Thus a protective coating of nitrocellulose varnish, a nitrocellulose film or a tube of smokeless powder — all are characterized by relatively high elasticity and mechanical strength. These properties are a direct consequence of the microstructure of cellulose, which is composed of highly oriented long-chain molecules of polysaccharide. Not only nitrocellulose, but also other derivatives of cellulose, such as other esters and ethers, demonstrate similar characteristics. 

Several studies have been made of LB films of esters of naturally occurring polysaccharides. Kawaguchi et al. [242] formed long chain esters of cellulose which, however, could only be formed into multilayers by the horizontal lifting technique. Schoondorp et al. [243] studied LB multilayers of esters of amylose and showed that materials with short alkyl side chains have a helical conformation at the air/water interface and that this structure can be transferred into multilayers. As in the case of the isotactic polymethylmethacrylate, the helical structure appears to lead to an oriented structure in the LB film. These two families of materials are illustrated in Figure 5.9. 

Cellulose esters of long-chain carboxylic acids (up to C2o) are described as interesting thermoplastic materials. An exhaustive review of all the synthesis methods... 

Cellulose esters and cellulose ethers are prepared based on the substitution of cellulose hydroxyl groups with short chain regents. Cellulose can also be modified by introduction of long chain polymer(s) onto its main chain. The products are mostly grafted copolymers, and in some cases, block copolymers can also be made. 

Extensive research into the thermal properties of long-chain cellulose esters (LCCE) has produced an understanding of the melt- and flow properties of fully as well as partially substituted derivatives. It is apparent that Tg declines quickly to between 50 and 150 C as acyl chain length exceeds that of butyrate (O Fig. 21). 

P. Jandura, B. V. Kokta, andB. Riedl, Fibrous long-chain organic acid cellulose esters and their characterization by difluse reflectance FTIR spectroscopy, solid-state CP/ MAS C-NMR, and X-ray dif action, /. Appl. Polym. Sci, 78 (2000) 1354-1365. 

A lot of plasticizers typically with two ester groups have been described in the literature [39] including aliphatic diesters of phthalic acid, like diethyl phthalate, and diesters of aliphatic dicarboxylic acids like dibutyl adipate or azelate [22] as well as glycerol triacetate (triacetin), citrate esters, and phosphates [39]. Although these kind of plasticizers work well for decades in various applications, the accelerated retention test shows [39] that exudation and volatilization must be taken into account and can cause changes in the material performance. Thus, attempts have been made to synthesize long-chain esters of cellulose (LCCEs) with acid chain lengths of up to 20 carbon atoms (see [21] and references cited therein), which could be processed without external plasticizers. Positive results are reported for cellulose acetate hexanoate and cellulose acetate nonanoate [21] but these esters did not go into production. 

The acylation of cellulose with acid chlorides in DMA/LiCl is most suitable for the homogeneous synthesis of readily soluble partially functionalized long-chain aliphatic esters and substituted acetic acid esters (Table 16.3). In contrast to the anhydrides, the fatty acid chlorides are soluble in the reaction mixture and soluble polysaccharide esters may be formed with a very high efficiency. Even in the case of stearoyl chloride, 79 per cent of the reagent is consumed for the esterification of cellulose. 

Edgar K.J., Pecorini T.J., Glasser W.G., Long-chain cellulose esters Preparation, properties, and perspective, in Cellulose Derivatives Modification, Characterisation, and Nanostructures, Eds. Heinze T.J. and Glasser W.G., ACS Symposium Series No. 688, American Chemical Society, Washington/DC, 1998, pp. 38-60. 

There are also some derivatives of cellulose and the most important one among them is cellulose esters. Cellulose esters are produced from esterification reactions at one or more of the three hydroxyl groups in its long chain structure and have the potential to participate in the carbon cycle via microbiologically catalysed... 

Thermal degradation behavioiu of some partially esterified long chain cellulose esters was studied by Jandura et al. [28], Cellulose esters showed lower decomposition temperature than cellulose. However, the thermal stability of cellulose esters, with the exemption of cellulose oleate, improved with higher degree of substitution. 

Some of the ester derivatives of polysaccharides, such as cellulose acetates or nitrates, are of considerable industrial importance (Chapter XII). Those of the sugars have not been commercialized to any great extent, with the possible exception of sucrose octaacetate. An important series of surface-active materials are provided by alditols and their anhydro derivatives partially esterified with long-chain fatty acids (Chapter VII). For the latter derivatives, increased solubility in water is provided by reaction with ethylene oxide. 

Starch derivatives have received less attention as compared with cellulose acetates. Among the promising packaging materials are long chain esters of starch [104]. Again, the details of degradation processes remain to be clarified. 

Ueno et al. [21] studied the antifogging effect of surfactants on transparent cellulose ester films. Nonionic fluorinated surfactants, applied as a monolayer, were more effective antifogging agents than the corresponding nonionic hydrocarbon surfactants. The surfaces of the thin film placed in a closed chamber filled with water vapor at 60°C remained transparent for a long time. The antifogging effect of nonionic fluorinated surfactants was attributed to a double stracture consisting of fluorocarbon and poly(ethylene oxide) chains in the monomolecular layer. 

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