Shaver, Michael

Love, Jason

Sinclair, Fern

Engineering and Physical Sciences Research Council (EPSRC)

2018-03-20T12:16:55Z

2018-03-20T12:16:55Z

2017-11-30

Poly(lactic acid), PLA, is a viable replacement to petroleum derived polymers due to its renewable feedstock, biodegradability and bioassimilability, yet improvements in its physical, thermal and mechanical properties are required before it can fully enter all commodity markets. This thesis investigates olefin cross-metathesis (CM) as a synthetic strategy to modify the properties of PLA. The use of novel lanthanide and actinide catalysts on the microstructure control of PLA are also explored. The Tebbe reagent was used in a new synthetic strategy to produce a novel olefin derivative of lactide (MML). Olefin CM of MML with hex-1-ene was successful but polymerisation pre- and post-CM was unsuccessful due to monomer instability. CM of another olefin derivative of lactide, 3-methylenated lactide (3-ML) was successful with aliphatic alkenes; hex-1-ene to dodec-1-ene. To overcome competing alcoholysis of the functionalised monomers, which prevented polymerisation, hydrogenation was used to remove the olefin entity followed by successful ring-opening polymerisation (ROP) to produce polymers of low glass-transition temperatures (Tg). Post-polymerisation CM on an olefin containing polymer P(β-heptenolactone) P(β-HL), with methyl acrylate and an epoxide, generated functionalised homopolymers with increased Tg’s. Co-polymerisation of lactide with β-HL generated novel gradient-copolymers. Olefin CM with 15 different cross-partners produced functionalised copolymers with different thermal properties. Based on this route a new methodology was created to introduce two unique functionalities into the polymer backbone by manipulation of the olefin reactivities. Finally, in a collaborative project, uranium and cerium catalysts, Me3SiOU(OArP)3 and Me3SiOCe(OArP)3 - designed out-with the group- were tested and compared as ROP catalysts for lactide. Both catalysts were active in living polymerisations of L-lactide and under immortal conditions the activity and rates of the catalysts were switched, accounted for by a change in the coordination sphere due to ligand displacement. ROP of rac-lactide using the uranium analogue produced heterotactic-biased PLA with a Pr = 0.79.

http://hdl.handle.net/1842/28896

en

The University of Edinburgh

F. Sinclair, J. A. Hilna, J. A. L. Wells, M. P. Shaver and P. L Arnold, Ring opening polymerisation of lactide with uranium(IV) and cerium(IV) phosphinoaryloxide complexes. Dalton transactions, 2017, 46, 10786-10790

F. Sinclair, M. Alkattan, J. Prunet and M. P. Shaver, Olefin cross metathesis and ringclosing metathesis in polymer chemistry, Polymer Chemistry, 2017, 8, 3385-3398

F. Sinclair, L. Chen, B. W. Greenland and M. P. Shaver, Installing Multiple Functional Groups on biodegradable Polyesters via Post-Polymerisation Olefin Cross-Metathesis, Macromolecules, 2016, 49, 6826-6834

poly(lactic acid)

PLA

olefin cross-metathesis

olefin moiety

lactide

olefin CM

cerium catalysts

uranium catalysts

Modification of poly(lactic acid) via Olefin cross-metathesis

Thesis or Dissertation

Doctoral

PhD Doctor of Philosophy