The abundantly available bio-polymer, cellulose, is virtually inexhaustible renewable raw material with fascinating properties. The chemical derivatization offers possibilities to obtain bio-based material with variety of properties, but the poor solubility of cellulose in organic solvents hampers the efficiency of modification reactions. However, direct acylation of cellulose can also be carried out under heterogeneous conditions to obtain high DS derivatives. When cellulose or pulp is suspended in dry pyridine and stirred under heating with aliphatic or aromatic acid chlorides, cellulose esters with high DS-values are obtained through reactive dissolution. We have systematically screened the direct acylation of cellulose and different pulps with various types of acid chlorides. The syntheses were started in a heterogeneous solid-liquid reaction medium in hot pyridine with aliphatic or aromatic acid chlorides. After a few hours�depending on the reagent used�a homogenous solution was obtained. The obtained cellulose esters show high degree of substitution (DS), degree of polymerization (DP), and good solubility in organic solvents. Softwood dissolving pulp (SWDP), hardwood kraft pulp (HWK) and hardwood kraft pulp-hemicellulose poor (HWKHP) have also been tested for their suitability to be transformed into cellulose esters via the same synthesis procedure. The results show that almost identical properties were obtained for pulp derivatives compared to microcrystalline cellulose esters. Thermal analysis of the synthesized materials showed an improved thermal stability compared to the original cellulose. The scanning electron microscopy (SEM) images of polymers showed a flat surface with an absence of fibrous structure. The reactive dissolution of cellulose or pulp reported herein makes them more practical starting materials for organic synthesis and material sciences.

Reactive dissolution of cellulose and pulp through acylation in pyridine

243rd National Meeting (2012)

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