The work presented in this thesis is focussed on the development of novel methodologies for use in controlling radical polymerisation reactions. The ability to exert control over polymerisation reactions is of great importance industrially. Chain transfer agents (CT As) are a classical method for controlling average molecular weight of polymer samples produced in reactions. Generally small organic molecules with a labile (abstractable) atom/group, CTAs can also be used to introduce functionality into a polymer chain. This thesis describes the synthesis and development of several families of chain transfer agent and examines their use in the polymerisation of methyl methacrylate (MMA) and styrene. Chapter 1 provides a general background to polymer chemistry, with an emphasis on radical polymerisation. A selection of the numerous methods of controlling polymerisation reactions are examined and their limitations discussed. The control systems of interest, namely ally lie (bromide and sulfide) CT As and RAFT agents are introduced and the ability for these systems to allow the introduction of functionality to the polymer backbone is highlighted. Novel initiation systems are also introduced, with manganese-based examples highlighted as being of interest. Chapter 2 examines allylic CTAs in more depth, with synthetic routes to allylic bromides examined and discussed. A range of allylic bromides are synthesised bearing a range of functional groups on the alkene bond. Similarly, a range of allylic sulfides are synthesised. The CTAs produced are then tested in the radical polymerisations of MMA and styrene. A range of conditions are employed, including conventional thermal and microwave, and a number of initiation systems tested, including dimanganese decacarbonyl and manganese(II) bromide. Chapter 3 probes reversible addition fragmentation chain transfer (RAFT), using dithioesters. As a pseudo-living radical polymerisation technique, RAFT can provide excellent control of the radical polymerisation reaction. The synthesis of RAFT agents bearing a range of functional groups is examined, and the effectiveness of the RAFT agents probed in radical polymerisation reactions using MMA and styrene. The possibility of using these RAFT agents as iniferters, so removing the need for a conventional initiator, is also examined. Chapter 4 looks to the future, exploring the possibility of postfuctionalisation of polymers capped with functionalised CT As. A number of reactions are examined, with some initial investigations into their applicability made. The ability to synthesise block copolymers is tested using RAFT-capped polymers, which have the ability to re-grow due to the pseudo-living nature of the RAFT system.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:550351 |
| Date | January 2008 |
| Creators | Hall, Daniel J. |
| Publisher | University of York |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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