pH-Responsive cagelike porous polymer microspheres prepared via consecutive RAFT polymerization induced by γ-ray radiation

Although RAFT polymerization in a homogeneous system has been widely studied, RAFT mediated polymerization on a solid–liquid surface has rarely been mentioned. In this work, a two-step consecutive RAFT polymerization of methyl methacrylate (MMA) and acrylic acid (AA) on the sulfonated polystyrene (SPS) microspheres dispersed in water was achieved under γ-ray radiation. As a result, poly(acrylic acid) (PAA)-grafted cagelike porous SPS/PMMA microspheres with distinct pH-responsive release properties have been fabricated. The RAFT mediated polymerization on the surface of porous microspheres has been discussed in detail based on the 1H NMR spectra combined with the 2D 1H–13C heteronuclear singular quantum correlation (HSQC) spectra. This work not only enriches the mechanism of heterogeneous surficial RAFT polymerization, but also indicates that γ-ray radiation induced RAFT mediated polymerization on a solid–liquid surface should be a practical technique for the fabrication of porous materials with subtle controllable surface properties.