Chemical and nanomechanical analysis of rice husk modified by ATRP-grafted oligomer

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Rice husk (RH), an abundant agricultural residue, was reacted with 2-bromoisobutyryl bromide, to convert it to a heterogeneous polyfunctional macroinitiator for Atom Transfer Radical Polymerization (ATRP). The number of active sites placed on the RH surface was small, but they were ATRP active. Non-polar methyl methacrylate (MMA) and polar acrylonitrile (AN) were polymerized from the RH, and a sequential monomer addition was used to prepare an amphiphilic PMMA-b-PAN copolymer on RH surface. FTIR qualitatively confirmed the grafting. Gravimetric and XPS analysis of the different RH surface compositions indicated thin layers of oligomeric PMMA, PAN, and PMMA-b-PAN. The modified surfaces were mapped by nanomechanical AFM to measure surface roughness, and adhesion and moduli using the Derjaguin-Muller-Toropov model. RH grafted with MMA possessed a roughness value of 7.92, and a hard and weakly adhering surface (13.1. GPa and 16.7. nN respectively) while RH grafted with AN yielded a roughness value of 29 with hardness and adhesion values of 4.0. GPa and 23.5. nN. The PMMA-b-PAN modification afforded a surface with a roughness value of 51.5. nm, with hardness and adhesion values of 3.0. GPa and 75.3. nN. © 2011 Elsevier Inc.

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Journal of Colloid and Interface Science