Preparation of Initiators for Sustainable Polymerisation

Abstract

Current plastics are mostly derived from petrochemical sources, as it is afinite resource renewable replacements are sought after. Polymers derived fromcyclic esters such as; lactide, valerolactone and caprolactone are of interest. Anindustrially viable method of producing stereocontrolled polylactide (PLA) fromrac-lactide is desired. Previous work on poly(cyclic esters) is overviewed inchapter 1 with an emphasis upon PLA.Chapter 2 reports the coordination of Ti(OiPr)4 to homo/piperazine bridgedbis(phenol) (salan) ligands. Under ambient conditions bimetallic structures wereproduced and a steric dependent equilibrium system is discussed. Forcing conditions resulted in monometallic homopiperazine salan complexes. Their application for the ring-opening-polymerisation (ROP) of rac-lactide is investigated. Homo/piperazine salan titanium catecholates were synthesised and their cytotoxicity investigated by collaborators.Chapter 3 details the synthesis of monometallic homopiperazine salanzirconium/hafnium isopropoxide complexes. Their utility for the ROP of rac-lactide in solution and solvent free systems are discussed. Bimetallic or tetrametallic solid state structures from attempts to coordinate Zr(IV)/Hf(IV) metals to piperazine salan ligands are also discussed.Chapter 4 discusses the complexation of AlMe3 with homopiperazine salanligands. The resulting monometallic complexes were inactive for the ROP of lactide. Benzyl alcohol derivatives were synthesised and trialled for solvent free ROP of rac-lactide, δ-valerolactone, ε-caprolactone. Co-polymerisations were investigated and a tri-block polymer of poly(ε-caprolactone/δ-valerolactone/rac-lactide) was prepared.Chapter 5, trans-1,4-DACH salen ligands were synthesised and investigatedas ligands with Al(III), Ti(IV), Zr(IV), and Zn(II) metal centres. Bimetallic Al(III)and Ti(IV) structures were characterised and trialled for the ROP of rac-lactide.Isotactic PLA was reported for aluminium complexes, dependent upon phenoxysubstituents, and these polymerisations were shown to be immortal in nature.Chapter 6 details the synthesis of trans-1,2-DACH salalen ligands whichwere complexed to AlMe3, these initiators were investigated for the solution ROP of rac-lactide. The further synthesis of benzyloxy derivatives is also reported and they were utilised for solution and solvent free polymerisations of rac-lactide. The initiator’s behaviour is discussed with respect to varying amine and imine groups.

Date of Award	23 May 2013
Original language	English
Awarding Institution	University of Bath
Supervisor	Matthew Jones (Supervisor)