Polyelectrolyte Brushes Grafted from Cellulose Nanocrystals Using Cu-Mediated Surface-Initiated Controlled Radical Polymerization

Abstract

Herein we report the synthesis of cellulose nanocrystals (CNCs) grafted with poly(acrylic acid) (PAA) chains of different lengths using Cu-mediated surface initiated-controlled radical polymerization (SI-CRP). First, poly(tert-butylacrylate) (PtBA) brushes were synthesized; then, subsequent acid hydrolysis was used to furnish PAA brushes tethered onto the CNC surfaces. The CNCs were chemically modified to create initiator moieties on the CNC surfaces using chemical vapor deposition (CVD) and continued in solvent phase in DMF. A density of initiator groups of 4.6 bromine ester groups/nm(2) on the CNC surface was reached, suggesting a dense functionalization and a promising starting point for the controlled/living radical polymerization. The SI-CRP of tert-butylacrylate proceeded in a well-controlled manner with the aid of added sacrificial initiator, yielding polymer brushes with polydispersity values typically well below 1.12. We calculated the polymer brush grafting density to almost 0.3 chains/nm(2), corresponding to high grafting densities and dense polymer brush formation on the nanocrystals. Successful rapid acid hydrolysis to remove the tert-butyl groups yielded pH-responsive PAA-polyelectrolyte brushes bound to the CNC surface. Individually dispersed rod-like nanoparticles with brushes of PtBA or PAA were clearly visualized by AFM and TEM imaging.

Functional nanomaterials through esterification of cellulose: a review of chemistry and application

“…Furthermore, a significant number of surface esterification reactions were used as precursors for further polymerization on the surface of nanocelluloses via ''grafting from'' approach. For instance, 2-bromoisobutyryl bromide (BriBB) as the initiator agent was attached to the hydroxyl groups of nanocellulose by esterification for further polymerization (Majoinen et al 2011;Wu et al 2015;Yi et al 2008). This strategy has been used extensively for the creation of initiating sites for the polymerization on the surface of nanocellulose.…”

The preparation of graft copolymers of cellulose and cellulose derivatives using ATRP under homogeneous reaction conditions

“…Heterogeneous conditions refer to situations where cellulose is not dissolved in the reaction medium so the reaction occurs at the interface between the solid and liquid phases resulting in modification only at the surface. Cellulose fibers 17,18 , membranes 19,20 and nano-whiskers 21,22 have all been modified under heterogeneous conditions. Homogeneous conditions are defined by the dissolution or, at least, by the swelling of cellulose in the reaction medium resulting in modification of the entire cellulose molecular structure.…”

Effect of surface-grafted cellulose nanocrystals on the thermal and mechanical properties of PLLA based nanocomposites

“…For example, functional sites from a reaction of 2-bromoisobutyrylbromide on the surface of nanocrystals initiated the polymerization of styrene by atom transfer radical polymerization (ATRP) [13]. The "grafting to" strategy has also been used to graft poly(N-isopropylacrylamide) [14], polyaniline [15], poly(acrylic acid) [16] and poly(ethylene oxide) [17]. Poly(ε-caprolactone) has been grafted onto cellulose nanocrystals by the ring opening polymerization (ROP) of monomer using citric acid as a catalyst [18][19][20].…”