Cellulose ethers are high molecular
weight compounds prepare by replacing hydrogen atoms of hydroxyl groups in the anhydroglucose units of cellulose with alkyl or
substituted alkyl groups. The commercially main properties of cellulose ethers
are determined by their molecular weights, chemical structure and distribution
of the substituent groups, the degree of
substitution (DS) and a molar
substitution. These properties normally contain solubility, viscosity in
solution, surface activity, thermoplastic film characteristics and stability
against biodegradation, heat, hydrolysis
and oxidation. The viscosity of cellulose
ether solutions is directly linked with
their molecular weights. The properties of cellulose ethers are controlled by
the degree of polymerization (DP) and degree of substitution . Examples of mostly used cellulose
ethers are Methylcellulose (MC),
Ethylcellulose (EC), Hydroxyethylcellulose (HEC), Hydroxypropylcellulose (HPC), hydroxypropylmethylcellulose (HPMC),
carboxymethylcellulose (CMC) and sodium carboxymethylcellulose (NaCMC) 9. Sodium
carboxymethylcellulose (NaCMC) is the most widely used cellulose ether,
prepared by the reaction of chloroacetic acid and cellulose, water-soluble, large DS range (usually
0.7-1.2), water solubility increases with DS, used in milk products, dressings,
jellies, syrups 10.


Synthesis of Carboxymethyl Cellulose

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Cellulose is a polymer with an
extremely high internal cohesive energy, due to its high content of hydroxyls functions. Consequently, it does not
dissolve readily either in common organic solvents
or in water. The use of the OH-function of cellulose yield one of the first semi-synthetic polymers (cellulose acetates,
nitrates, etc.). Sodium carboxymethylcellulose
is also a cellulose derivative, produced by the etherification of the hydroxyl group of cellulose macromolecules by monochloroacetic acid (MCA). Sodium carboxymethylcellulose synthesized for the
first time in 1920, and it is the most used cellulose derivative 11.


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