pH-Responsive Cellulose Nanocrystal Gels and Nanocomposites.

Autor:	Way AE; Department of Macromolecular Science and Engineering, Case Western Reserve University, 2100 Adelbert Road, Cleveland, Ohio 44106, United States., Hsu L; Department of Macromolecular Science and Engineering, Case Western Reserve University, 2100 Adelbert Road, Cleveland, Ohio 44106, United States., Shanmuganathan K; Department of Macromolecular Science and Engineering, Case Western Reserve University, 2100 Adelbert Road, Cleveland, Ohio 44106, United States., Weder C; Polymer Chemistry and Materials, Adolphe Merkle Institute, University of Fribourg, Rte de l'Ancienne Papeterie, CH-1723 Marly 1, Switzerland., Rowan SJ; Department of Macromolecular Science and Engineering, Case Western Reserve University, 2100 Adelbert Road, Cleveland, Ohio 44106, United States.
Jazyk:	angličtina
Zdroj:	ACS macro letters [ACS Macro Lett] 2012 Aug 21; Vol. 1 (8), pp. 1001-1006. Date of Electronic Publication: 2012 Jul 20.
DOI:	10.1021/mz3003006
Abstrakt:	We show that functionalization of the surface of cellulose nanocrystals (CNCs) with either carboxylic acid (CNC-CO 2 H) or amine (CNC-NH 2 ) moieties renders the CNCs pH-responsive. At low pH, where the amine groups are protonated, CNC-NH 2 forms aqueous dispersions in water on account of electrostatic repulsions of the ammonium moieties inhibiting aggregation. However, a transition to hydrogels is observed at higher pH where the CNC-NH 2 are neutral and the attractive forces based on hydrogen bonding dominate. The opposite behavior is observed for CNC-CO 2 H, which are dispersible at high pH and form gels in an acidic environment. We further show that these pH-responsive CNCs can be incorporated into a poly(vinyl acetate) matrix to yield mechanically adaptive pH-responsive nanocomposite films.
Databáze:	MEDLINE
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