Cellulose carboxylate/tosylate mixed esters: Synthesis, properties and shaping into microspheres

• Cellulose carboxylates/tosylate (acetate/butanoate/hexanoate) were synthesized.
• Determination of degree of substitution DSCarboxy by FTIR and UV–vis was studied.
• The IR peak area and frequency (CO and SO) depend linearly on DSCarboxy.
• Empirical polarity of ester films depend linearly on DSCarboxy.
• These mixed cellulose esters were shaped into homogeneous nanospheres.

Cellulose carboxylate/tosylate mixed esters (Cel-Carboxy/Ts) were synthesized with constant degree of tosylation, DSTs = 0.98 and variable degree of acylation, DSCarboxy; acetate, butanoate, and hexanoate. The tosylate (Cel-Ts) was prepared by reacting cellulose with tosyl chloride in presence of trimethylamine. The mixed esters were obtained by reacting Cel-Ts with carboxylic acid anhydride. The dependence of the following on DSCarboxy was investigated: IR data, including νCO, νSO and peak area (CO); empirical polarity of the films, determined by an adsorbed perichromic dye. We employed these parameters to determine DSCarboxy. Relative to ester saponification, these spectroscopic methods are convenient, expedient, and require much less sample. Mixed esters prepared physically from cellulose tosylate and tosylate/acetate behave only qualitatively similar to (Cel-Carboxy/Ts). The mixed esters were dissolved in acetone and regenerated in water as homogeneous microspheres.