Water-soluble cellulose ether substitution

A number of water-soluble cellulose ethers are marketed." Methyl cellulose is prepared by a method similar to that used for ethyl cellulose. A degree of substitution of 1.6-1.8 is usual since the resultant ether is soluble in cold water but not in hot. It is used as a thickening agent and emulsifier in cosmetics, as a paper size, in pharmaceuticals, in ceramics and in leather tanning operations. 

Properties. Sodium carboxymethylcellulose [9004-32-4] (CMC), also known as cellulose gum, is an anionic, water-soluble cellulose ether available in a wide range of substitution. The most widely used types are in the 0.7-1.2 DS range. Water solubility is achieved as the DS approaches 0.6 as the DS increases, solubility increases. The rate at which CMC dissolves depends primarily on its particle size. Finely ground material dissolves faster than coarser grades. The coarse material. 

Methylcellulose is a water-soluble cellulose derivative in which approximately 26-33% of the hydroxyl groups are in the form of the methyl ether. The different methylcellu-loses show varying degrees of substitution (between 1.4-2.0) and MW (10,000-220,000 Da) [27]. The solubility, as well as other polymer properties, depends on how uniform the methoxyl groups are distributed along the polymeric chain. In matrix tablets, methylcellulose is normally used in combination with HPMC. 

Occasionally, water-soluble plastics are required. Poly(vinyl alcohol) is commonly the first to be considered but some cellulose ethers, polyethylene oxides, poly(vinyl pyrrolidone) and A-substituted polyamides are among many possible alternatives. 

Semisynthetic gels are also very useful for the creation of drug delivery systems. Cellulose ethers are particularly important in drug delivery. These compounds are made by derivatizing the cellulose hydroxyls with various groups such as hydroxypropyl, methyl, or carboxymethyl. This substitution breaks up the crystallinity of native cellulose and makes it water-soluble [23], The degree... 

Cellulose ethers of a high degree of substitution are stable, relatively nonflammable, resistant to ultra-violet light and compatible with a wide range of solvents and plasticizers. Certain ethers of a low degree of substitution are soluble in water or alkali. It would appear from these properties that cellulose ethers should be ideally adapted for use in the plastics field and for many other uses. 

Treatment of alkali cellulose with sodium chloroacetate results in an ether with a free carboxyl group. This ether, in the form of its sodium salt, is water-soluble even when the degree of substitution is relatively low. Since the alkali-soluble modification of this substance is of much greater industrial importance it will be discussed in detail under that heading. 

A new class of water-soluble materials [10,11], was developed as a result of such design parameters that will be referred to as double substituted cationic cellulose ethers (DCEs). These materials contain both a cationic substituent and a hydrophobic substituent, attached to a cellulose ether backbone. The use of a double-substituted hydrophobe modified cationic polysaccharide is fundamentally different from current commercial vaginal formulations, which rely exclusively on nonionic or anionic vehicles. 

Cellulose may be converted from a water-insoluble polymer to a water-soluble polymer by the partial etherification of some of the hydroxyl groups by dimethyl sulfate. When the degree of substitution (DS) is 1.5 to 2.0, the hydrogen bonds are sufficiently weakened, and the methylcellulose is soluble in water. Carboxymethyl ethers, such as carboxymethylcellulose (CMC), are also water-soluble. The degree of solubility is related to the DS of the polymer and the pH of the solvent. 

The simplest representatives of cellulose ethers are the corresponding alkyl derivatives. The most common representatives manufactured industrially are methyl- and ethylcellulose. Methylcellulose is soluble in cold water when the DS is 1.4 to 2.0, whereas nearly completely substituted products (DS 2.4-2.8) are insoluble in water but soluble in organic solvents. 

Hydroxypropyl Cellulose occurs as a white powder. It is a cellulose ether containing hydroxypropyl substitution. It may contain a suitable anticaking agent. It is soluble in water and in certain organic solvents. 

Methylcellulose is a cellulose ether in which methyl groups have been substituted for hydroxyl groups on the 2-glucopyranose residues. It is soluble in cold water at low methoxy contents increased substitution increases the solubility in hydroalcoholic and alcoholic solutions.f ... 

Ethylcellulose is an ethyl ether of cellulose containing 44-51% of ethoxyl groups. It is insoluble in water but soluble in chloroform and in alcohol. It is possible to form water-soluble grades with a lower degree of substitution. 

CAS 9004-32-4. A semisynthetic, water-soluble polymer in which CH2COOH groups are substituted on the glucose units of the cellulose chain through an ether linkage. Mw ranges from 21,000 to 500,000. Since the reaction occurs in an alkaline medium, the product is the sodium salt of the carboxylic acid R-0-CH2COON a. 

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