The Synthesis and Characterisation of Novel Amide Initiators for the ATRP of OEGMA

Whilst atom transfer radical polymerisation (ATRP) has been shown to be a robust and versatile technique for the creation of a wide range of polymers from many different initiators, there is relatively little previous research into the usage of initiators containing amide functionality. Low initiator efficiencies, often resulting in higher than predicted molecular weight parameters, and slow polymerisations with variable rates of reaction are generally reported when amide initiators have previously been used. Various reasons have been proposed in the literature for poor performance of amide initiators including; interactions of the catalytic system of ATRP and the amide bond in the initiator, the irreversible loss of catalyst activity, a rapid initiation causing an overabundance of radicals and poor initiator efficiencies. No suitable solution for these problems had been put forward and the poor performance observed was a major hindrance for any work with amide initiators.

This work describes the development of a system that enabled the usage of novel amide initiators for the ATRP of oligo (ethylene glycol) methyl ether methacrylate (OEGMA) with high levels of success. The development of an ideal set of reactions conditions was shown to produce materials with low dispersities and molecular weight parameters in close agreement to theoretical values. Through the usage of UV-visible spectroscopy and quantum chemical calculations the reason for poor amide initiator performance was determined to be as a result of the high bond dissociation energy of the initiator's halide as a result of its proximity to the amide bond. This effect could be mitigated, but not eliminated, by performing reactions in polar solvent systems. Optimised reaction conditions were utilised in the synthesis of a block copolymer of POEGMA and polyethyleneimine, which shows potential as a stabiliser for superparamagnetic nanoparticles and as a controlled drug delivery system due to the materials high solubility and thermoresponsive properties.