4 years ago

Synthesis of dual thermo- and pH-sensitive poly (N-isopropylacrylamide-co-acrylic acid)-grafted cellulose nanocrystals by reversible addition-fragmentation chain transfer polymerization

Hossein Roghani-Mamaqani, Elnaz Zeinali, Vahid Haddadi-Asl
Free and cellulose nanocrystals (CNC)-grafted block copolymers of acrylic acid and N-isopropylacrylamide with various poly (N-isopropylacrylamide) (PNIPAAm) block lengths as dual temperature- and pH-sensitive materials were synthesized by RAFT polymerization via an R-approach method. Controlling LCST of the products by changing the PNIPAAm block length, addition of CNC, and variation of pH was studied. The free and CNC-grafted block copolymers were analyzed by Fourier transform infrared and proton nuclear magnetic resonance. Lower critical solution temperature (LCST) of copolymers was measured by dynamic light scattering using their hydrodynamic diameters. The block copolymers reversibly form core-corona structure with PNIPAAm as core and poly (acrylic acid) (PAA) as shell above LCST at higher pH values. LCST point shifts to higher temperatures by increasing pH and CNC content and also lowering PNIPAAm block length. By decreasing pH below 4 at certainly low temperatures, PAA becomes core and PNIPAAm forms corona. Thermal behaviour of the CNC-grafted polymers was studied by thermal gravimetric analysis and differential scanning calorimetry. Morphology of the polymer-grafted CNC was examined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. This article is protected by copyright. All rights reserved.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/jbm.a.36230

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