Abstract: Plasticized cellulose polymers comprise a base polymer having a chain of .beta.-anhydroglucose units joined by ether linkages and having ether substituents, with at least one of the units being additionally substituted, by esterification of at least one hydroxyl group, by at least one ester group, which contains at least two carbon atoms and is chemically unreactive.Preferably the ester group contains four or more, most preferably five, carbon atoms. The carbon chains of the ester groups may be straight or branched.These internally plasticized celluloses may be prepared by, for example, reacting the base polymer with a carboxylic acid in xylene or with an acid chloride or anhydride in pyridine. They are useful in particular as inhibitor coatings for rocket motor propellants and in general wherever cellulose polymers are employed.