The field of polymer chemistry is currently experiencing major research efforts into development of novel techniques for synthesis of polymers with well-controlled microstructure. Recently, a new method has been reported [McHale et al., Nat. Chem. 2012, 4, 491-497] whereby high molecular weight and low dispersity polymer can be obtained by a radical polymerization process via the use of solely physico-chemical interactions. This work was based on the combination of H-bonding templated polymerization confined within nanoreactors of self-assembled block copolymers. Herein, this system is thoroughly investigated to fully elucidate the underlying mechanism. Modification of physico-chemical parameters, kinetic parameters as well as observations of size exclusion chromatography (SEC) results and colloidal behavior in various solvents provide revised insights into the mechanism. Through detailed NMR and SEC investigations, it is demonstrated that the SEC secondary peak originally believed to be the high molecular weight "daughter" polymer actually corresponds to nanoparticles containing the daughter polymer. (C) 2017 Wiley Periodicals, Inc.