Core-shell nanogels by RAFT crosslinking polymerization: Synthesis and characterization

A synthetic methodology is described for the preparation of core–shell nanogels by reversible addition‐fragmentation chain transfer. Well‐defined macro chain transfer agents (macro‐CTA's) were prepared in a first step using monomers that yield sensitive polymers. In the second step, a crosslinker alone or with the addition of a functionalized comonomer were used to form a crosslinked core. The ratio of crosslinker to macro‐CTA is crucial to yield nanogels. Furthermore, the polymerization time has an impact in the architecture of the nanomaterial obtained: it evolves from a core‐crosslinked star to a core–shell nanogel. Controlling the molecular weight of the macro‐CTA and the type of comonomer in the core forming step, core–shell nanogels with hydrodynamic diameters from 22 to 168 nm and a core that represents from 35 to 77% of the size, were prepared containing functional groups in the core which could be used as catalytic scaffolds. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012. The reversible addition‐fragmentation chain transfer technique was used to prepare core–shell nanogels with large crosslinked core by radical crosslinking copolymerization in homogeneous phase. A dithiobenzoate (CTA) with a terminal OH group was used to prepare macro‐CTAs from PNIPAAm or statistical copolymers (N‐isopropylacrylamide/acid comonomers) with prescribed molecular weights. Macro‐CTA and a mixture of divinylbenzene and comonomers ((meth)acrylates) were used to synthesize core–shell nanogels with large hydrophobic functionalized core. The comonomers in the core provide the nanogels with functional groups for specific interactions with small molecules. Nanogels were soluble in organic medium and dispersible in aqueous medium. These macromolecules have potential application as catalytic scaffolds.