title: 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.
authors: Molecular Materials, Department of Applied Physics, Aalto University, P.O. Box 15100, FIN-00076 Aalto, Espoo, Finland.
authors: Johanna
authors: J
authors: Majoinen
authors: Andreas
authors: A
authors: Walther
authors: Jason R
authors: JR
authors: McKee
authors: Eero
authors: E
authors: Kontturi
authors: Vladimir
authors: V
authors: Aseyev
authors: Jani Markus
authors: JM
authors: Malho
authors: Janne
authors: J
authors: Ruokolainen
authors: Olli
authors: O
authors: Ikkala
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D002850:Chromatography, Gel; D003300:Copper / Q000737:chemistry*; D004573:Electrolytes / Q000737:chemistry*; D004951:Esterification; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D053758:Nanoparticles; D011108:Polymers / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013499:Surface Properties
chemical_list: D004573:Electrolytes; D011108:Polymers; D003300:Copper; D002482:Cellulose