The traditional heterogeneous liquid-state modifications of cellulose are already well studied, for those low-cost reactions that are performed industrially . One of the most successful commercial reactions is acetylation, typically performed using low-cost acetic anhydride and acetic acid, with sulfuric acid as catalyst ). This method has been shown in key articles to yield cellulose triacetate (CTA), where the outer fibril chains are converted to CTA, followed by a progressive conversion of the inner chains towards the core (Sassi and Chanzy 1995). In the industrial process, lower DS values are only accessible by applying a 'ripening' stage, where water is added to the batch reaction to hydrolyse some of the acetate esters. Clearly this method cannot preserve the crystallinity and morphology of the native materials, which are often so critical for application.