title: Poly(N-isopropylacrylamide) brushes grafted from cellulose nanocrystals via surface-initiated single-electron transfer living radical polymerization.
abstract: Cellulose nanocrystals (CNCs) or nanowhiskers produced from sulfuric acid hydrolysis of ramie fibers were used as substrates for surface chemical functionalization with thermoresponsive macromolecules. The CNCs were grafted with poly(N-isopropylacrylamide) brushes via surface-initiated single-electron transfer living radical polymerization (SI-SET-LRP) under various conditions at room temperature. The grafting process was confirmed via Fourier transform IR spectroscopy and X-ray photoelectron spectroscopy and the different molecular masses of the grafts were quantified and found to depend on the initiator and monomer concentrations used. No observable damage occurred to the CNCs after grafting, as determined by X-ray diffraction. Size exclusion chromatography analyses of polymer chains cleaved from the cellulose nanocrystals indicated that a higher degree of polymerization was achieved by increasing initiator or monomer loading, most likely caused by local heterogeneities yielding higher rates of polymerization. It is expected that suspension stability, interfacial interactions, friction, and other properties of grafted CNCs can be controlled by changes in temperature and provide a unique platform for further development of stimuli-responsive nanomaterials.
authors.affiliation: Departments of Forest Biomaterials and Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA.
authors.forename: Justin O
authors.initials: JO
authors.lastname: Zoppe
authors.forename: Youssef
authors.initials: Y
authors.lastname: Habibi
authors.forename: Orlando J
authors.initials: OJ
authors.lastname: Rojas
authors.forename: Richard A
authors.initials: RA
authors.lastname: Venditti
authors.forename: Leena-Sisko
authors.initials: LS
authors.lastname: Johansson
authors.forename: Kirill
authors.initials: K
authors.lastname: Efimenko
authors.forename: Monika
authors.initials: M
authors.lastname: Osterberg
authors.forename: Janne
authors.initials: J
authors.lastname: Laine
mesh_terms: D000178:Acrylamides / Q000138:chemical synthesis* / Q000737:chemistry*; D000180:Acrylic Resins; D032402:Boehmeria / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D002482:Cellulose / Q000737:chemistry*; D002850:Chromatography, Gel; D004579:Electron Transport; D053758:Nanoparticles / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D058105:Polymerization; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D000178:Acrylamides; D000180:Acrylic Resins; D011108:Polymers; C052970:poly-N-isopropylacrylamide; D002482:Cellulose