Hydroxypropyl cellulose (HPC) is a derivative of

cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...

with both water solubility and organic solubility. It is used as an excipient; a topical ophthalmic protectant and lubricant; a thickener, emulsifier, and stabilizer in cosmetic formulations; a sieving matrix for DNA separations by capillary and microchip electrophoresis; a leather consolidant used in book preservation; and a wood consolidant.

Chemistry

HPC is an

ether In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R� ...

of cellulose in which some of the

hydroxyl group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

s in the repeating

glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...

units have been hydroxypropylated forming -OCH₂CH(OH)CH₃ groups using

propylene oxide Propylene oxide is an epoxide with the molecular formula C3H6O. This colourless volatile liquid with an odour similar to ether, is produced on a large scale industrially. Its major application is its use for the production of polyether polyols f ...

. The average number of substituted hydroxyl groups per

unit is referred to as the degree of substitution (DS). Complete substitution would provide a DS of 3. Because the hydroxypropyl group added contains a hydroxyl group, this can also be etherified during preparation of HPC. When this occurs, the number of moles of hydroxypropyl groups per glucose ring, moles of substitution (MS), can be higher than 3. Because cellulose is very crystalline, HPC must have an MS about 4 in order to reach a good solubility in water. HPC has a combination of

hydrophobic In chemistry, hydrophobicity is the chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thu ...

and

hydrophilic A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press. In contrast, hydrophobes are n ...

groups, so it has a lower critical solution temperature (LCST) at 45 °C. At temperatures below the LCST, HPC is readily soluble in water; above the LCST, HPC is not soluble. HPC forms liquid crystals and many mesophases according to its concentration in water. Such mesophases include

isotropic In physics and geometry, isotropy () is uniformity in all orientations. Precise definitions depend on the subject area. Exceptions, or inequalities, are frequently indicated by the prefix ' or ', hence '' anisotropy''. ''Anisotropy'' is also ...

anisotropic Anisotropy () is the structural property of non-uniformity in different directions, as opposed to isotropy. An anisotropic object or pattern has properties that differ according to direction of measurement. For example, many materials exhibit ver ...

, nematic and cholesteric. The last one gives many colors such as violet, green and red.

Uses

Lacrisert, manufactured by Aton Pharma, is a formulation of HPC used for artificial

tears Tears are a clear liquid secreted by the lacrimal glands (tear gland) found in the eyes of all land mammals. Tears are made up of water, electrolytes, proteins, lipids, and mucins that form layers on the surface of eyes. The different types of ...

. It is used to treat medical conditions characterized by insufficient tear production such as keratoconjunctivitis sicca), recurrent corneal erosions, decreased corneal sensitivity, exposure and neuroparalytic keratitis. HPC is also used as a lubricant for artificial eyes. HPC is used as a thickener, a low level binder and as an

emulsion An emulsion is a mixture of two or more liquids that are normally Miscibility, immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloi ...

stabiliser with

E number E numbers, short for Europe numbers, are codes for substances used as food additives, including those found naturally in many foods, such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly ...

E463. In pharmaceuticals it is used as a binder in tablets. HPC is used as a sieving matrix for DNA separations by capillary and microchip electrophoresis. HPC is used as a thickener, emulsifier, and stabilizer in cosmetic formulations such as shampoos, conditioners, and lotions. HPC is the main ingredient in Cellugel, described as a "safe, penetrating consolidant for leather book covers affected by red rot" by Preservation Solutions, and used in book conservation. HPC was used by conservators at the Firearms Museum at the Buffalo Bill Center of the West on the Forgotten Winchester, a Winchester Model 1873 lever-action centerfire rifle discovered in 2014 leaning against a tree in Great Basin National Park,

Nevada Nevada ( ; ) is a landlocked state in the Western United States. It borders Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the seventh-most extensive, th ...

.Forgotten Winchester visits the Center of the West’s Cody Firearms Museum
Buffalo Bill Center of the West

Notes and references

{{DEFAULTSORT:Hydroxypropyl Cellulose Excipients Cellulose Cellulose ethers E-number additives

Chemistry

Uses

See also

Notes and references