Towards sequence controlled functional polyesters : advances in the ring-opening (co)polymerisation of large ring and Σ-subsituted lactones

• Main Author: Wilson, James
• Published: University of Warwick 2015
• Subjects: 547; QD Chemistry
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682927

This thesis reports studies into the ring-opening polymerisation (ROP) of large ring lactones (macrolactones) and e-substituted e-lactones (eSLs). Additionally, the copolymerisations of these monomers with other lactones were investigated in order to determine the conditions that define the sequencing of lactone copolymers. The ability to produce one-pot lactone copolymers with tuneable properties is explored and carried forward to introduce functional groups for post-polymerisation functionalisation. The ability to produce sequence controlled block copolymers using only lactone monomers is also outlined for the first time in this thesis. Chapter 1 provides an overview for the current published literature on the ROP of macrolactones, including the factors that affect macrolactone polymerisation and copolymerisation with a variety of other monomers. In Chapter 2, the ‘immortal’ ROP (iROP) of the macrolactone, ω-pentadecalactone (PDL), is demonstrated with the use of a Mg catalyst. The technique is shown to be achievable in a non-inert environment, with no undesired side reactions affecting the properties of the final polymers compared to polymers produced in an inert environment. Furthermore, the catalyst is demonstrated to be able to ‘immortally’ polymerise smaller ring lactones. Chapter 3 describes the copolymerisation of PDL with a variety of lactones of smaller ring-sizes. The sequencing of the copolymers is characterised throughout the copolymerisation using quantitative 13C NMR spectroscopy and demonstrates the randomisation of the polymer sequencing in each case. The thermal and crystalline properties of the copolymers is explored and optimised in order to produce PDL copolymers with independently tuneable thermal and degradative properties. In Chapter 4, the copolymerisation of PDL with the eSL, menthide (MI), is examined and shown to produce a copolymer with a block-like sequencing. This sequencing is demonstrated in the case of PDL copolymerisation with other eSL monomers. This discovery is then used in order to produce a block copolymer of PDL with an alkene functionalised eSL. The ability of this copolymer to undergo post-polymerisation modification is demonstrated through thiol-ene addition onto the pendent alkene groups. Chapter 5 goes on to use MI in copolymerisations with other non-substituted lactones in order to determine the factors that affect the sequencing of eSL copolymers. The production of macrolactone/eSL copolymers with a random sequencing is then attempted. The sequencing of copolymers produced from two eSLs is also demonstrated to produce block-like copolymers. As a consequence of the large difference in reactivity between eSLs, the potential for sequence controlled lactone copolymers is established. A general summary of Chapters 2 - 5 is presented in Chapter 6, with the concluding findings outlined.