Cu(0)-mediated RDRP : synthesis of multiblock copolymers and mechanistic studies

Doctoral thesis English OPEN
Alsubaie, Fehaid
  • Subject: QD

The aim of this work is to investigate the versatility of Cu(0)-mediated reversible deactivation radical polymerisation (RDRP) in aqueous media in order to facilitate the synthesis of multiblock copolymers consisting of various acrylamides. Under carefully optimised conditions, a simple and highly efficient one-pot polymerisation procedure (full conversion for each block and no intermediate purification required) will be developed allowing access to iterative monomer additions, fast polymerisation rates and high level of control. As a result, complex microstructures (such as hexablocks) can be achieved in a quantitative manner in a matter of few hours, which consists the fastest synthesis of such material up to date.\ud \ud However, the loss of the halide chain end will be shown to be the main limitation of the in situ chain extensions and block copolymerisations of acrylamides in water. In order to assess the effect of the nature of the monomer to the loss of the end group fidelity, a further investigation into the monomer nature and the lifetime of the ω-Br chain end will be conducted further highlighting the importance to monomer structure and sequence in poly(acrylamide)s multiblocks in order to maximise the retention of the bromine chain end.\ud \ud At the second part of this thesis, a mechanistic investigation of Cu(0)-mediated polymerisation in organic and aqueous media will also be presented. The role of the Cu(0) on the polymerisation kinetics and will be extensively investigated differentiating Cu(0)-wire from the in situ generated Cu(0) particles. The extent of disproportionation and comproportionation reactions in aqueous, organic and aqueous/organic mixtures will be also evaluated and the effect of the monomer on these reactions will also be shown demonstrating a completely different behaviour between organic and aqueous media. Finally, a direct comparison between Cu(0) and Cu(I) mediated polymerisation under exactly the same reaction conditions will be attempted indicating different active species depending on the conditions employed.\ud \ud Nevertheless and regardless the mechanism, the ideal polymerisation protocol that allows access to the preparation of high ordered materials will be shown. Very fast polymerisation rates (achieving quantitative conversion within 10 min), high end group fidelity even at full monomer conversion and good control over the molecular weight distribution will highlight Cu(0)-mediated polymerisation as a versatile tool for the synthesis of a wide range of materials.
  • References (5)

    Figure 1. Examples of current synthetic polymers existing in different areas............4 Figure 2. The evolution of molecular weight with increasing conversion for step growth polymers. .........................................................................................................6 Figure 3. The evolution of molecular weight with increasing conversion for chain growth polymers. .........................................................................................................7 Figure 4. The evolution of molecular weight with increasing conversion for living chain polymers...........................................................................................................16 Figure 5. A selection of bidentate and multi-dentate nitrogen-based ligands developed for Cu(I)X mediated ATRP42, 43. ..............................................................27 Figure 6. Monomers polymerisable by NMP and ATRP in aqueous solution. ........46 Chapter 1:

    Scheme 1. Schematic of a typical aqueous SET-LRP proceeding with disproportionation of CuBr/Me6TREN prior to monomer/initiator addition in pure water at 0°C as described by reference 55.................................................................61 Scheme 2. Synthesis of multiblock homopolymers of NIPAM by iterative SET-LRP in pure H2O. ...............................................................................................................65 Scheme 4. Synthesis of alternating block copolymers composed of NIPAM and HEAA by iterative SET-LRP in H2O. [M]0 : [I]0 : [CuBr] : [Me6TREN] = [10] : [1] : [0.04] : [0.04].............................................................................................................74 Scheme 5. Synthesis of multiblock homopolymers of HEAA by iterative SET-LRP in pure H2O at 0ºC. ....................................................................................................78 Chapter 3:

    Scheme 1. Termination via formation of a cyclic onium species as described by Brittain. ......................................................................................................................94 Chapter 4:

    Table 1. Comparison of the various processes between SET-LRP and SARA-ATRP, reproduced from reference 133..................................................................................40 Chapter 2:

    Table 1. Preparation of multiblock homopolymers prepared by sequential addition of deoxygenated aliquots of aqueous NIPAM (10 eq) to PNIPAM during SET-LRP at 0ºC in H2O. [M]0 : [I]0 : [CuBr] : [Me6TREN] = [10] : [1] : [0.04] : [0.04]..........62 Table 2. Optimisation of multiblock homopolymers prepared by sequential addition of deoxygenated aliquots of aqueous NIPAM (10 eq) to PNIPAM during SET-LRP at 0°C in H2O. [M]0 : [I]0 : [CuBr] : [Me6TREN] = [10] : [1] : [0.04] : [0.04]. ........65 Table 3. Preparation of multiblock copolymers composed of NIPAM DMA and HEAA by iterative aqueous SET-LRP at 0°C in H2O. [M]0 : [I]0 : [CuBr] : [Me6TREN] = [10] : [1] : [0.04] : [0.04]. ..................................................................70 Table 4. Preparation of alternating block copolymers composed of NIPAM and HEAA by iterative SET-LRP in H2O. [M]0 : [I]0 : [CuBr] : [Me6TREN] = [10] : [1] : [0.04] : [0.04].............................................................................................................74 Chapter 3:

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