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Recent Work by Matthew Davidson: Synthesis and Structure of Initiators for ROP of Cyclic Esters

Recent Work by Matthew Davidson: Synthesis and Structure of Initiators for ROP of Cyclic Esters. July 21, 2008. Development of Polymerization Catalysts. Environmentally and biologically benign metals (Group 2 and Group 4 metals)

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Recent Work by Matthew Davidson: Synthesis and Structure of Initiators for ROP of Cyclic Esters

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  1. Recent Work by Matthew Davidson: Synthesis and Structure of Initiators for ROP of Cyclic Esters July 21, 2008

  2. Development of Polymerization Catalysts • Environmentally and biologically benign metals (Group 2 and Group 4 metals) • Ligands leading to high polymerization control and tunable physical properties

  3. Synthesis of a Barium Amine Bis(phenolate) Complex Davidson, M. G.; O’Hara, C. T.; Jones, M. D; Keir, C. G.; Mahon, M. F.; Kociok-Kohn, G.; Inorg. Chem.2007, 46, 7686-7688

  4. Crystal Structure of 1-Ba • Distinct trinuclear barium species • Monoclinic space group C2/c • 1H and 13C{1H} NMR show dynamic processes in toluene and benzene • Spectra are much simpler in the more coordinating solvent, THF Davidson, M. G.; O’Hara, C. T.; Jones, M. D; Keir, C. G.; Mahon, M. F.; Kociok-Kohn, G.; Inorg. Chem.2007, 46, 7686-7688

  5. ROP of L-Lactide and e-Caprolactone with 1-Ba • e-CL • In toluene solution at ambient temperature • Monomer:Initiator = 300:1 • L-LA • Melt at 130°C • Monomer:Initiator = 900:1 • High viscosity prevents increased conversion (60% yield after 3.5 h) • PDI = 1.57, Mn = 25,500 ROP of e-CL by 1-Ba Davidson, M. G.; O’Hara, C. T.; Jones, M. D; Keir, C. G.; Mahon, M. F.; Kociok-Kohn, G.; Inorg. Chem.2007, 46, 7686-7688

  6. Catalyst Kinetics • Polymerization occurs with first-order kinetics with respect to the monomer • As determined by 1H NMR Davidson, M. G.; O’Hara, C. T.; Jones, M. D; Keir, C. G.; Mahon, M. F.; Kociok-Kohn, G.; Inorg. Chem.2007, 46, 7686-7688

  7. Group 4 Metal Alkoxide Initiators • Six coordinate, pseudo-octahedral complexes • Phenoxides are mutually trans; imine and alkoxide groups are mutally cis (a-cis geometry) • NMR confirms the solid state structure Chmura, A. J.; Cousins, D. M.; Davidson, M. G.; Jones, M. D.; Lunn, M. D.; Mahon, M. F.; Dalton Transactions2008, 1437-1443

  8. Determination of Polymerization Control for ROP of rac-Lactide • In toluene solution • 80°C for 2 h or 20°C for 24 h • Monomer:Initiator ratio = 100:1 • Solvent-Free • 130°C for 0.5 h • Monomer:Initiator ratio = 300:1 • GPC for determination of Mw, Mn • Homonuclear decoupled 1H NMR for determination of Pr (tacticity) Solution polymerization study using (R-4)2Zr(OiPr)2 Chmura, A. J.; Cousins, D. M.; Davidson, M. G.; Jones, M. D.; Lunn, M. D.; Mahon, M. F.; Dalton Transactions2008, 1437-1443

  9. Solution Polymerization of rac-lactide Chmura, A. J.; Cousins, D. M.; Davidson, M. G.; Jones, M. D.; Lunn, M. D.; Mahon, M. F.; Dalton Transactions2008, 1437-1443

  10. Solvent-Free Polymerization of rac-Lactide Chmura, A. J.; Cousins, D. M.; Davidson, M. G.; Jones, M. D.; Lunn, M. D.; Mahon, M. F.; Dalton Transactions2008, 1437-1443

  11. Results • Ti is inactive, while Zr complexes are active as initiators for ROP of rac-lactide at 80°C and 20°C in solution • Both Ti and Zr are active in solvent-free conditions, producing higher yields and but larger PDI • Activity and selectivity are independent of ligand substitution, with all showing moderate heterotactic selectivity Chmura, A. J.; Cousins, D. M.; Davidson, M. G.; Jones, M. D.; Lunn, M. D.; Mahon, M. F.; Dalton Transactions2008, 1437-1443

  12. Homogeneous Models for Heterogeneous Catalysts Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. C. Dalton Transactions,2008, 3655-3657

  13. Characterizing the Homogeneous Models • Complex 2 is triclinic P-1 • 1H/13C/29Si NMR agree with solid state structure • Complex 3 is dimeric • 1H/29Si NMR agrees with previously reported results Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. C. Dalton Transactions,2008, 3655-3657

  14. Heterogeneous Catalysts for ROP of rac-Lactide • Goal: Reduce catalyst residue in the polymers • SiO2 (40 Å or 60 Å) was reacted with Ti(OiPr)4 or Al(OiPr)3 and heated to 70°C for 4 h • ICP-AES reveals Ti loading = 3.40% Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. C. Dalton Transactions,2008, 3655-3657

  15. Melt Polymerizations of rac-Lactide Ti-silsesquioxane complexes: 1110 ppm Ti in polymer residues Ti–heterogeneous catalysts: 15 ppm Ti in polymer residues *Determined by ICP-AES Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. C. Dalton Transactions,2008, 3655-3657

  16. References • Davidson, M. G.; O’Hara, C. T.; Jones, M. D; Keir, C. G.; Mahon, M. F.; Kociok-Kohn, G.; Inorg. Chem.2007, 46, 7686-7688 • Chmura, A. J.; Cousins, D. M.; Davidson, M. G.; Jones, M. D.; Lunn, M. D.; Mahon, M. F.; Dalton Transactions2008, 1437-1443 • Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. C. Dalton Transactions,2008, 3655-3657

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