Derivatives
The hydroxyl groups (-OH) of cellulose can be partially or fully reacted with various reagents to afford derivatives with useful properties like mainly cellulose esters and cellulose ethers (-OR). In principle, though not always in current industrial practice, cellulosic polymers are renewable resources.
Ester derivatives include:
Cellulose ester | Reagent | Example | Reagent | Group R |
---|---|---|---|---|
Organic esters | Organic acids | Cellulose acetate | Acetic acid and acetic anhydride | H or -(C=O)CH3 |
Cellulose triacetate | Acetic acid and acetic anhydride | -(C=O)CH3 | ||
Cellulose propionate | Propanoic acid | H or -(C=O)CH2CH3 | ||
Cellulose acetate propionate | Acetic acid and propanoic acid | H or -(C=O)CH3 or -(C=O)CH2CH3 | ||
Cellulose acetate butyrate | Acetic acid and butyric acid | H or -(C=O)CH3 or -(C=O)CH2CH2CH3 | ||
Inorganic esters | Inorganic acids | Nitrocellulose (cellulose nitrate) | Nitric acid or another powerful nitrating agent | H or -NO2 |
Cellulose sulfate | Sulfuric acid or another powerful sulfuring agent | H or -SO3H |
The cellulose acetate and cellulose triacetate are film- and fiber-forming materials that find a variety of uses. The nitrocellulose was initially used as an explosive and was an early film forming material. With camphor, nitrocellulose gives celluloid.
Ether derivatives include:
Cellulose ethers | Reagent | Example | Reagent | Group R = H or | Water solubility | Application | E number |
---|---|---|---|---|---|---|---|
Alkyl | Halogenoalkanes | Methylcellulose | Chloromethane | -CH3 | Cold water soluble | E461 | |
Ethylcellulose | Chloroethane | -CH2CH3 | Water insoluble | A commercial thermoplastic used in coatings, inks, binders, and controlled-release drug tablets | E462 | ||
Ethyl methyl cellulose | Chloromethane and chloroethane | -CH3 or -CH2CH3 | E465 | ||||
Hydroxyalkyl | Epoxides | Hydroxyethyl cellulose | Ethylene oxide | -CH2CH2OH | Cold/hot water soluble | Gelling and thickening agent | |
Hydroxypropyl cellulose (HPC) | Propylene oxide | -CH2CH(OH)CH3 | Cold water soluble | E463 | |||
Hydroxyethyl methyl cellulose | Chloromethane and ethylene oxide | -CH3 or -CH2CH2OH | Cold water soluble | Production of cellulose films | |||
Hydroxypropyl methyl cellulose (HPMC) | Chloromethane and propylene oxide | -CH3 or -CH2CH(OH)CH3 | Cold water soluble | Viscosity modifier, gelling, foaming and binding agent | E464 | ||
Ethyl hydroxyethyl cellulose | Chloroethane and ethylene oxide | -CH2CH3 or—CH2CH2OH | E467 | ||||
Carboxyalkyl | Halogenated carboxylic acids | Carboxymethyl cellulose (CMC) | Chloroacetic acid | -CH2COOH | Cold/Hot water soluble | Often used as its sodium salt, sodium carboxymethyl cellulose (NaCMC) | E466 |
The sodium carboxymethyl cellulose can be cross-linked to give the croscarmellose sodium (E468) for use as a disintegrant in pharmaceutical formulations.
Read more about this topic: Cellulose