CARBOXYMETHYLCELLULOSE: CHARACTERISTICS, STRUCTURE, SYNTHESIS, USES - CHEMISTRY - 2025

The carboxymethyl cellulose is a compound derived from cellulose, a polymer of glucose. It also receives the names of cellulose or carmellose gum. It can be in the form of sodium salt.

Carboxymethylcellulose is hygroscopic and soluble in water, unlike cellulose, which is insoluble in water. Some –CH ₂ OH groups of the glucose molecules that make up cellulose are substituted by –CH ₂ OCH ₂ COOH groups. This substitution gives ionic properties to its structure.

Source: By LHcheM, from Wikimedia Commons

But what is cellulose? It is a biopolymer made up exclusively of β-glucose molecules, linked by β-1,4-o-glucosidic bonds. Cellulose has the formula (C ₆ H ₁₀ O ₅) _n with a minimum value of 2000 for n. The polymer can have a linear or fibrous structure, being the main constituent of the plant cell wall.

Its compact structure is impenetrable by water and therefore insoluble in it. Despite being made up of glucose, cellulose cannot be used by animals, since they lack the cellulase enzyme to break the β1,4-glucosidic bonds.

The carboxymethyl group attached to cellulose gives carboxymethylcellulose a negatively charged surface. These charges allow its use in the ion exchange chromatography technique, functioning as a cation exchanger that is used in the purification of proteins.

Due to its hydrophilic property, carboxymethylcellulose is used in the treatment of dry eyes. Likewise, due to this property, it has been used in the manufacture of diapers and sanitary products of this type. These applications serve as an example of the enormous list of uses and / or applications that this compound has.

Physical and chemical characteristics

Formula

RnOCH ₂ -COOH

Physical appearance

White powder. Sodium carboxymethyl cellulose: white or milky fibrous particles.

Smell and taste

Odorless and tasteless.

Water solubility

It is soluble (20 mg / mL).

Solubility in organic solvents

It is insoluble in methanol, ethanol, diethyl ether, acetone, chloroform, and also in benzene.

Decomposition point

274 ° C.

Density

0.7 - 0.9 g / cm ³.

Acidity

It is similar to acetic acid and its dissociation constant is 5 x 10 ^-5.

Structure

Source: By Elrond, from Wikimedia Commons

The upper image shows the structure of a carboxymethylcellulose monomer unit. Note that the H of the hydroxyl groups are substituted by the CH ₂ COOH groups; Except for the OH group at C-3. That is, according to the image, the polymer is not completely substituted.

CH ₂ COOH groups can deprotonate and surround themselves by electrostatic attraction of Na ⁺ cations: CH ₂ COO ^- Na ⁺. It is thanks to them that carboxymethylcellulose is very soluble in water, as it is capable of forming hydrogen bonds with it (CH ₂ COOH-OH ₂). This is the main cause of its marked hydrophilic and hygroscopic character.

Also, these groups are much more voluminous than the hydroxyls, so that the physicochemical properties of the polymer change with respect to the original cellulose. Its large size prevents the formation of internal hydrogen bonds, that is, between the monomeric chains, leaving the rings totally exposed to interactions with water.

Therefore, the greater the degree of substitution of OH by CH ₂ COOH, the greater the hydrophilic character of the resulting cellulose. Microscopically this difference may not be very obvious; but on macroscopic scales, it would be equal to being able to dissolve a block of wood in a container of water if such substitutions occurred on the spot.

Synthesis

To obtain carboxymethylcellulose, from cellulose fibers, the Druvacell procedure is followed:

A) The cellulose fibers are treated with isopropanol and alkalis in order to cause their swelling and the ionization of the hydroxyl groups.

B) The cellulose fibers from the previous treatment are further alkalized by treatment with NaOH, according to the following reaction:

RceOH + NaOH => RceOH ∙ NaOH

C) Cellulose fibers bound to NaOH then react with sodium chloroacetate, thus producing sodium carboxymethylcellulose:

RceOH ∙ NaOH + ClCH ₂ COO ^- Na => RceOCH ₂ COO ^- Na ⁺ + NaCl + H ₂ O

Binding of the COO ^- group to cellulose to form carboxymethiclulose makes it soluble in water and more reactive.

What is it for (uses)

Carboxymethylcellulose has numerous uses and applications due to its hydrophilicity and its ability to combine with numerous compounds. Among its uses are the following.

Foods

-It is used as a thickener and stabilizer for food. In addition, it is used as a dietary fiber and emulsifier. It is used in the shake of ice cream, creams and creams, as well as an aid in the formation of gelatin gels and puddings.

-Used as a suspending agent in fruit juices and as a protective colloid in mayonnaise. It is also used to cover the surface of fruits.

-Because carboxymethylcellulose is not metabolized by the body, it can be used by people on a low-calorie diet.

Medicine

-Carboxymethylcellulose solutions form gels used in heart, thoracic and corneal surgeries.

-In chest operations, the lungs are stapled and covered with a carboxymethylcellulose solution. This in order to avoid leaks of the air contained in the alveoli and the entry of fluids into the lungs.

-In the branch of orthopedics, carboxymethylcellulose is used in the lubrication of the joints, especially in the wrists, knees and hips. The polymer solution is injected into the joints to prevent erosion, inflammation, and possible destruction of cartilage.

-It is used in the treatment of dryness and eye irritation. It is also used as a protective agent to prevent damage to the eyeball, such as can occur in the placement of contact lenses.

-Carboxymethylcellulose is also used in the treatment of constipation, favoring the formation of feces with the appropriate consistency. It is used as a laxative.

-A combination of carboxymethylcellulose-heparin has been used to prevent adhesion during surgeries.

Construction Industry

-Acts as a stabilizing and hydrophilic agent in most cement preparations and construction materials. It improves the dispersion of sand in the cement, in addition it increases the adhesive action of the cement.

-It is also used as part of the adhesives for upholstery papers.

In detergents

The branch of industry that perhaps has the highest consumption of carboxymethylcellulose is in the production of soaps and detergents. It acts as an inhibiting agent that prevents fats, removed from the surface of fabrics by detergents, from rejoining them.

Adhesives

-It is used in the elaboration of adhesives for the paper, since it does not stain it, it does not give off an odor and it is removable. This makes it ideal for use in repairing books or other materials.

-It has also been tested in mixtures with starch and phenol formaldehyde for the elaboration of glues that allow the union of wood sheets.

Wine industry

It is used to avoid the precipitation of the tartaric salts present in the wine.

Paper industry

-The coating with carboxymethylcellulose preparations of waxed papers and cardboard reduces the consumption of waxes. It also reduces the consumption of printing ink, resulting in higher gloss surfaces. In addition, the surface of the paper has greater smoothness and greater resistance to grease.

-Carboxymethylcellulose improves the bond between the paper fibers, improving their coloring. It is also used as an auxiliary dispersant in the extrusion of the fibers of the cellulose pulp, avoiding their flocculation.

farming

Carboxymethylcellulose acts as a dispersing agent for pesticides. Also, it is used as a glue to bond the insecticide to the surface of plant leaves. On some occasions, it is used as an aid in the degradation of some highly polluting fertilizers.

Cosmetics

It is used as a thickener, stabilizer and film former in creams, lotions, shampoos and hair care products. In addition, it is used in the preparation of gels for use in dental cleaning.

Paints

It is used in the production of oil-based paints and varnishes, acting as a thickening and dispersing agent for pigments in fluids.

Plastics

It is used to increase the viscosity of latex.

Ceramics

It is used to join porcelain pieces, since carboxymethylcellulose solutions originate when baking few ashes.

Textile industry

-It is used in its raw form to avoid deformation of the fabrics. Carboxymethylcellulose, in combination with starch, is used in laundries. It is also used in the finishing of fabrics. During their manufacture, the fabrics are impregnated with carboxymethylcellulose and then treated with acid and heat.

-It is used in the printing of fabrics, collaborating as a thickening agent for textile paints and varnishes.

Pharmaceutical industry

-Carboxymethylcellulose is used in the coating of medicine tablets. The polymer is insoluble in acidic stomach conditions, but soluble in the small intestine, where therapeutic agents are absorbed.

-It is also used as a gel former, drug carriers in the form of ointments. Furthermore, it is used as a stabilizing agent in suspensions and emulsions. It is used as a bioadhesive in tablets that bind to body mucus.

References

1. Sidley Chemical. (2018). Properties of Sodium Carboxymethyl Cellulose. Recovered from: celluloseether.com
2. Wikipedia. (2018). Carboxymethylcellulose. Recovered from: es.wikipedia.org
3. QuimiNet. (October 11, 2006). The various applications of carboxymethylcellulose. Recovered from: quiminet.com
4. Gamboni J. & col. (sf). Optimization of the carboxymethylation process of cellulose from sugarcane bagasse.. Recovered from: aaiq.org.ar
5. A carboxymethylellulose-heparin combination for the prevention of surgical adhesions. (2017) The Journal of surgical research 213: 222-233.