Chapter 1 introduces the concept of polyethylene (PE) end-functionalisation as a route to block copolymers, reviews the different literature methods for their synthesis this way, and compares the advantages and disadvantages of each. Finally, an existing method which makes use of PE terminated with a styrene derivative is identified as having fewer disadvantages than most literature procedures. Further investigation of the mechanism is proposed. Chapter 2 focusses on the different types of so-called dormant state formed in Ziegler-Natta catalysed olefin polymerisations, and in particular on the dormancy occurring after styrene insertion. Copolymerisations of ethylene with styrene, allylbenzene and 4-phenyl-1-butene in the presence of hydrogen are undertaken, and evidence for the presence of a dormant state or simply competitive rates of hydrogenation vs ethylene insertion is discussed. Increasing styrene concentration beyond that used by Chung is found to yield PE capped at both chain ends with styrene. A new mechanism – Catalytic Hydride Initiated Polymerisation (CHIP) – is consistent with these new observations. Chapter 3 focusses on extending the application of the CHIP mechanism to the synthesis of new examples of end-functional PE. Copolymerisations of ethylene with α-methylstyrene and related monomers 1,3/1,4-diisopropenylbenzene, α-methylstyrene dimer and limonene in the presence of hydrogen are investigated, resulting in the successful synthesis of a range of PE examples initiated with each comonomer. The effects of hydrogen pressure and comonomer concentration are also discussed. The advantages of CHIP are discussed, and the synthesis of end-functionalised PE incorporating DIB is studied in detail. An α-methylstyrene like end group is present at the start of the PE chains. Chapter 4 describes the free-radical copolymerisation of the new functionalised PE with acrylate monomers. Observations are consistent with a new reversible termination mechanism similar to nitroxide mediated polymerisation. The products are characterised by NMR, GPC, DLS, TEM and DSC, and the evidence is found to be consistent with the presence of block copolymers. Chapter 5 details the experimental procedures used to carry out the work in this thesis.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:618949 |
| Date | January 2014 |
| Creators | Kay, Christopher James |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/62620/ |
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