Alteration of the cellulose nanocrystal surface chemistry for guided formation of polymer brushes

Abstract

Grafting polymers using Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) from cellulose nanocrystals (CNC) has proven to be an efficient technique for controlling the dispersion of CNC in non-polar solvents and hydrophobic polymer matrices and introducing desired properties of a polymer to CNC. A commonly described initial step to enable the grafting of polymers from CNC is through the esterification of cellulose with 2-bromoisobutyryl bromide (BiBB). Here we demonstrate an optimized approach for the esterification while controlling the degree of substitution of the BiBB initiator, maintaining the rod-like morphology, cellulose I structure, and minimal loss of the crystallinity index value. Understanding how reaction variables control and impact the characteristic properties of CNC and the degree of substitution will assist with tailoring the surface modification and, as a result, tuning the CNC–polymer brush systems properties for advanced applications across different industries, including flexible electronics and biomedical.