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Abstract
One of the long-term goals of polymer chemistry is to develop techniques for synthesis of polymers with exact molecular weight (MW) along with precise control over microstructure. Recently, a new approach based on template polymerisation and block copolymers (BCP) self-assembled into nanoreactors has been reported [McHale et al, Nature Chemistry. 2012, 4 (6), 491 497]. The method utilises a combination of hydrogen bonding templated radical polymerisation (TRP) within micellar nanoreactors to synthesise daughter polymers of high MW with low dispersity. Size exclusion chromatography (SEC) analysis of the TRPs in nanoreactors show the daughter polymer eluting as a secondary peak before the elution of the BCPs that are used to form nanoreactors and act as templates.
In this work, the ability of BCPs to self-assemble into nanoreactors suitable for template polymerisation is investigated with respect to block lengths and overall MW of BCPs, as well as type of solvents and temperature. TRP in nanoreactors is subsequently investigated through modification of various physical-chemical parameters (solvent and BCP chain lengths and composition), and kinetic parameters (temperature, time, monomer, monomer concentration and initiator concentration of polymerisation) to provide insight into the polymerisation mechanism. SEC, 1H nuclear magnetic resonance (1H NMR) and dynamic light scattering (DLS) investigations of various TRPs in nanoreactors clearly demonstrated that the secondary SEC peak, originally attributed to pure daughter polymer, is in fact consisting of nanoparticles of daughter polymer and the template BCPs. Despite the claims of the original work being invalidated, the results of this study did imply that polymerisation via a templating mechanism within segregated micellar nanoreactors is occurring and further work is necessary to elucidate the product of the polymerisations.