Controllable acetylation of cellulose nanocrystal by uniform design and response surface methodology

Acetylation of Cellulose nanocrystal (CNC) can reduce its surface polarity and therefore extends its application in biomedical and chemical fields. A method combining uniform design (UD) and response surface methodology (RSM) was developed to produce the acetylated CNC with arbitrary degree of substitution (DS) and crystallinity index (CrI). The effects of three factors (i.e., temperature, reaction time and the volume of acetic anhydride) on DS and CrI were investigated in their respective ranges (i.e., 60-90 oC, 1.0-5.0 h and 1.0-5.0 mL). Both mathematical models for DS and CrI were developed by multiple stepwise regression (MSR) based on UD data and their significances were evaluated by analysis of variance. The controllable acetylation of CNC was realized by using either UD alone or the combination of UD and RSM. Eight verification experiments show that the relative errors between the predicted and the measured results are less than 16.77 % and 6.08 % for DS and CrI, respectively, confirming the reliability and validity of the method. This developed methodology is ingenious and expected to be expanded to any other fields that controllable preparations are required.