Preparation of core–shell attapulgite particles by redox-initiated surface reversible addition–fragmentation chain transfer polymerization via a “graft from” approach

Nanoclay attapulgite (ATP) was first activated with hydrochloric acid to enhance the surface reactivity, and was then allowed to react with a synthetic aromatic tertiary amine coupling agent to introduce electron-donor groups. Subsequently, the surface-initiated reversible addition–fragmentation chain transfer (SI-RAFT) polymerization of methyl methacrylate (MMA) was carried out in the presence of a free RAFT agent cyanoisopropyl dithiobenzoate (CPDB) initiated by a redox pair made up of benzoyl peroxide (BPO) and aromatic tertiary amine functionalized ATP (ATP-ATA). The grafting process was verified by 1H nuclear magnetic resonance, UV-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, thermo gravimetric analysis, transmission electron microscopy and gel permeation chromatography. Kinetic behavior indicated that polymerization using this redox initiation system displayed a living/controlled nature. Both the grafted and free polymers were grown in a controlled manner, and the RAFT polymerization proceeded with 37.6% monomer conversion achieved within 10 h at 50 °C, yielding about 47.4% grafting ratio of polymer relative to hybrid particles with high affinity to organic media.