Synthesis and Characterization of All Acrylic Block Copolymer/Clay Nanocomposites Prepared via Surface Initiated Atom Transfer Radical Polymerization (SI-ATRP)
journal contributionposted on 25.07.2012, 00:00 by Dhruba J. Haloi, Souvik Ata, Nikhil K. Singha
Surface initiated polymerization (SIP) is an emerging powerful tool to modify and tailor the surface properties of nanoparticles. Among different methods of SIP, surface initiated atom transfer radical polymerization (SI-ATRP) has several strategic advantages over other methods of polymerizations. This investigation reports the preparation and characterization of poly(2-ethylhexyl acrylate) (PEHA)/clay nanocomposite from nanoclay surface via SI-ATRP and poly(2-ethylhexyl acrylate)-block-poly(methyl methacrylate) (PEHA-b-PMMA)/clay nanocomposite via conventional ATRP. To carry out SI-ATRP, the nanoclay (Cloisite Na+) surface was first modified by incorporating an ATRP initiator (2-bromopropionyl bromide) to nanoclay surface via a grafting reaction. The prepared bromo-functionalized nanoclay (Clay–Br) was then used to carry out SI-ATRP of 2-ethylhexyl acrylate (EHA) at 90 °C using CuBr as catalyst in combination with N, N, N′, N″, N″- pentamethyl diethylenetriamine (PMDETA) as the ligand. The macroinitiator (clay-PEHA-Br) was used to prepare PEHA-b-PMMA/clay nanocomposites via conventional ATRP using the same reaction conditions as SI-ATRP of EHA. A series of PEHA-b-PMMA/clay nanocomposites were prepared via ATRP. The prepared PEHA/clay nanocomposites and PEHA-b-PMMA/clay nanocomposites were characterized by WAXD and TEM analyses. DSC analysis of PEHA-b-PMMA/clay nanocomposites showed two Tg values corresponding to two blocks present in the block copolymers. TGA analysis was also carried out to study the thermal stability of PEHA/clay nanocomposites and PEHA-b-PMMA/clay nanocomposites at different nanoclay loading. The chemical structure and molecular weights of the prepared polymers were analyzed by Fourier transform infrared (FT-IR), 1H NMR, and gel permeation chromatography (GPC) analyses.