Aqueous RAFT polymerisation of acrylamide monomers

The challenge of this project was to control the polymerisation of acrylamide monomers, particularly sodium 2-acrylamido-2-methylpropane sulfonate (Lubrizol trademark, AMPS®2405), via reversible addition-fragmentation chain transfer (RAFT) polymerisation in aqueous solution. AMPS® based polymers are employed in a wide range of applications (e.g. medical, paint, oil recovery and water treatment), and are typically obtained via conventional radical polymerisation. Here, the use of the RAFT process to control the polymerisation of AMPS®2405 was reported, and well-defined polymeric architectures were obtained compared to materials obtained via free radical polymerisation (FRP). The chain transfer agent (CTA) of choice for this project was initially DDMAT (CTA-A, Z-group is C12H25), and a water soluble CTA synthesised by the Lubrizol corporation (USA) in tonne-scale. DDMAT is known to form aggregates in water ([CAC]DDMAT =0.005 M) and this is likely to disrupt the RAFT mechanism and consequently diminish the control over the polymerisation. To overcome this problem a chain transfer agent with a shorter alkyl chain (BDMAT, Z-group is C4H9) was used for comparison with DDMAT. The polymerisation of AMPS®2405 monomer was optimised, as discussed in CHAPTER 2, in aqueous solution using either DDMAT or BDMAT as a chain transfer agent. These conditions were found to be universal to other water soluble acrylamide monomers (N,N-dimethylacrylamide, N-hydroxyethyl acrylamide and 4-acryloylmorpholine). More complex architectures were designed, as described in CHAPTER 3, exploiting the high chain end fidelity and chain extensions. A small library of diblock copolymers using various comonomers (N,N-dimethylacrylamide, N-hydroxyethyl acrylamide, 4-acryloylmorpholine, acrylic acid and acrylamide) were first synthesised. The synthesis of star polymers using the arm first approach was further studied, and well-defined multiblock star copolymers were obtained by RAFT polymerisation. These structures synthesised were characterised, as discussed in CHAPTER 4, using diverse techniques (e.g. SAXS, DLS, SEC with triple detection and AFM). While copolymers prepared from AMPS®2405 can be used in numerous applications, the focus of this thesis, as discussed in CHAPTER 5, was to study their benefit as heparin-mimicking polymers