Cellulose cross-linkages

To prepare croscarmellose sodium, crude cellulose is steeped in sodium hydroxide solution [1] and treated with sodium monochloroacetate to form carboxymethylcellu-lose sodium. After completion of the reaction, the excess sodium monochloroacetate slowly hydrolyzes to glycolic acid. The glycolic acid converts a few of the sodium earboxymethyl groups to the free acid and catalyzes the cross-linkage to form croscarmellose sodium. The by-products sodium chloride and sodium glycolate can be removed by extraction with alcohol to achieve 99.5% purity. Croscarmellose sodium may be milled to break the polymer fibers into shorter lengths and hence improve flow properties. 

The possibility of the presence of cross linkages in the molecular structure of cellulose has been indicated by the work of Heuser, in cellulose nitrate by the work of McBain and Scott, and, by inference, in cellulose acetate. It is evident that the conclusions which have been drawn from studies of the reducing and non-reducing end groups in... 

Notes The solid support of the stationary phase is known as the matrix, which includes cellulose, dextran, agarose, polyacrylamide, silica, polystyrene, polyvinyl, polyether and resins. The matrix of differing porosity and stability varies in the degree of cross-linkages. It is modified to confer specific properties the chemical attachment of various functional groups. 

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