recent work by matthew davidson: synthesis and structure of initiators for rop of cyclic esters

Recent Work by Recent Work by Matthew Davidson: Matthew Davidson:

Synthesis and Structure Synthesis and Structure of Initiators for ROP of of Initiators for ROP of

Cyclic EstersCyclic Esters

July 21, 2008July 21, 2008

Development of Polymerization Development of Polymerization CatalystsCatalysts

►Environmentally and biologically Environmentally and biologically benign metals (Group 2 and Group 4 benign metals (Group 2 and Group 4 metals)metals)

►Ligands leading to high polymerization Ligands leading to high polymerization control and tunable physical propertiescontrol and tunable physical properties

Synthesis of a Barium Amine Synthesis of a Barium Amine Bis(phenolate) ComplexBis(phenolate) Complex

Davidson, M. G.; O’Hara, C. T.; Jones, M. D; Keir, C. G.; Mahon, M. F.; Davidson, M. G.; O’Hara, C. T.; Jones, M. D; Keir, C. G.; Mahon, M. F.; Kociok-Kohn, G.; Kociok-Kohn, G.; Inorg. Chem.Inorg. Chem. 20072007, 46, 7686-7688, 46, 7686-7688

Crystal Structure of Crystal Structure of 11-Ba-Ba

► Distinct trinuclear Distinct trinuclear barium speciesbarium species

► Monoclinic space group Monoclinic space group C2/cC2/c

► 11H and H and 1313C{C{11H} NMR H} NMR show dynamic show dynamic processes in toluene processes in toluene and benzeneand benzene

► Spectra are much Spectra are much simpler in the more simpler in the more coordinating solvent, coordinating solvent, THFTHF


ROP of ROP of LL-Lactide and -Lactide and --Caprolactone with 1-BaCaprolactone with 1-Ba

► -CL-CL In toluene solution at In toluene solution at

ambient temperatureambient temperature Monomer:Initiator = Monomer:Initiator =

300:1300:1► LL-LA-LA

Melt at 130Melt at 130°°CC Monomer:Initiator = Monomer:Initiator =

900:1900:1 High viscosity High viscosity

prevents increased prevents increased conversion (60% conversion (60% yield after 3.5 h)yield after 3.5 h)

PDI = 1.57, MPDI = 1.57, Mnn = = 25,50025,500

ROP of -CL by 1-Ba


Catalyst KineticsCatalyst Kinetics

► Polymerization Polymerization occurs with occurs with first-order first-order kinetics with kinetics with respect to the respect to the monomermonomer As determined As determined

by by 11H NMRH NMR


Group 4 Metal Alkoxide InitiatorsGroup 4 Metal Alkoxide Initiators

► Six coordinate, pseudo-octahedral Six coordinate, pseudo-octahedral complexes complexes

► Phenoxides are mutually Phenoxides are mutually transtrans; imine and ; imine and alkoxide groups are mutally alkoxide groups are mutally ciscis ( (--ciscis geometry)geometry)

► NMR confirms the solid state structureNMR confirms the solid state structureChmura, A. J.; Cousins, D. M.; Davidson, M. G.; Jones, M. D.; Lunn, M. D.; Chmura, A. J.; Cousins, D. M.; Davidson, M. G.; Jones, M. D.; Lunn, M. D.;

Mahon, M. F.; Mahon, M. F.; Dalton TransactionsDalton Transactions 20082008, 1437-1443, 1437-1443

Determination of Polymerization Determination of Polymerization Control for ROP of Control for ROP of racrac-Lactide-Lactide

► In toluene solutionIn toluene solution 8080°°C for 2 h or 20C for 2 h or 20°°C C

for 24 hfor 24 h Monomer:Initiator ratio Monomer:Initiator ratio

= 100:1= 100:1► Solvent-FreeSolvent-Free

130130°°C for 0.5 hC for 0.5 h Monomer:Initiator ratio Monomer:Initiator ratio

= 300:1= 300:1► GPC for determination GPC for determination

of Mof Mww, M, Mnn

► Homonuclear Homonuclear decoupled decoupled 11H NMR for H NMR for determination of Pdetermination of Prr (tacticity)(tacticity)

Chmura, A. J.; Cousins, D. M.; Davidson, M. G.; Jones, M. D.; Lunn, M. D.; Chmura, A. J.; Cousins, D. M.; Davidson, M. G.; Jones, M. D.; Lunn, M. D.; Mahon, M. F.; Mahon, M. F.; Dalton TransactionsDalton Transactions 20082008, 1437-1443, 1437-1443

Solution polymerization study using (R-4)2Zr(OiPr)2

Solution Polymerization of Solution Polymerization of racrac--lactidelactide


Solvent-Free Polymerization of Solvent-Free Polymerization of racrac-Lactide-Lactide


ResultsResults► Ti is inactive, while Zr complexes are Ti is inactive, while Zr complexes are

active as initiators for ROP of active as initiators for ROP of racrac-lactide at -lactide at 8080°C and 20°C°C and 20°C in solution in solution

► Both Ti and Zr are active in solvent-free Both Ti and Zr are active in solvent-free conditions, producing higher yields and conditions, producing higher yields and but larger PDIbut larger PDI

► Activity and selectivity are independent of Activity and selectivity are independent of ligand substitution, with all showing ligand substitution, with all showing moderate heterotactic selectivitymoderate heterotactic selectivity


Homogeneous Models for Homogeneous Models for Heterogeneous CatalystsHeterogeneous Catalysts

Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. C. C. Dalton Transactions,Dalton Transactions, 20082008, 3655-3657, 3655-3657

Characterizing the Characterizing the Homogeneous ModelsHomogeneous Models

►ComplexComplex 2 2 is triclinic is triclinic P-P-11►11H/H/1313C/C/2929Si NMR agree with solid state Si NMR agree with solid state

structurestructure►Complex Complex 33 is dimeric is dimeric►11H/H/2929Si NMR agrees with previously Si NMR agrees with previously

reported resultsreported results

Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. C. C. Dalton Transactions,Dalton Transactions, 20082008, 3655-3657, 3655-3657

Heterogeneous Catalysts for Heterogeneous Catalysts for ROP of ROP of racrac-Lactide-Lactide

►Goal: Reduce catalyst residue in the Goal: Reduce catalyst residue in the polymerspolymers

►SiOSiO22 (40 Å or 60 Å) was reacted with (40 Å or 60 Å) was reacted with Ti(OTi(OiiPr)Pr)44 or Al(O or Al(OiiPr)Pr)33 and heated to and heated to 7070°°C for 4 hC for 4 h

► ICP-AES reveals Ti loading = 3.40%ICP-AES reveals Ti loading = 3.40%

Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. C. D. C. Dalton Transactions,Dalton Transactions, 20082008, 3655-3657, 3655-3657

Melt Polymerizations of Melt Polymerizations of racrac--LactideLactide

InitiatorInitiator Time/hTime/h YieldYield MMnn MMww MMnn/M/Mww PPrr

22 4848 55 24,50024,500 81,40081,400 3.33.3 0.50.5

33 0.50.5 8383 200,500200,500 506,200506,200 2.52.5 0.550.55

Ti–SiOTi–SiO22 (60) (60) 22 7878 47,95047,950 48,95048,950 1.021.02 0.50.5

Ti–SiOTi–SiO22 (60) (60) 66 9898 65,65065,650 92,00092,000 1.401.40 0.50.5

Ti–SiOTi–SiO22 (40) (40) 22 5252 14,70014,700 15,90015,900 1.081.08 0.50.5

Ti–SiOTi–SiO22 (40) (40) 66 5858 16,55016,550 18,50018,500 1.121.12 0.50.5

Al–SiOAl–SiO22 (60)(60)

4848 1010 3,0003,000 4,0504,050 1.131.13 0.250.25

Ti-silsesquioxane complexes: 1110 ppm Ti in polymer residuesTi–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, Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. C. D. C. Dalton Transactions,Dalton Transactions, 20082008, 3655-3657, 3655-3657

ReferencesReferences

► Davidson, M. G.; O’Hara, C. T.; Jones, M. D; Keir, C. Davidson, M. G.; O’Hara, C. T.; Jones, M. D; Keir, C. G.; Mahon, M. F.; Kociok-Kohn, G.; G.; Mahon, M. F.; Kociok-Kohn, G.; Inorg. Chem.Inorg. Chem. 20072007, 46, 7686-7688, 46, 7686-7688

► Chmura, A. J.; Cousins, D. M.; Davidson, M. G.; Chmura, A. J.; Cousins, D. M.; Davidson, M. G.; Jones, M. D.; Lunn, M. D.; Mahon, M. F.; Jones, M. D.; Lunn, M. D.; Mahon, M. F.; Dalton Dalton TransactionsTransactions 20082008, 1437-1443, 1437-1443

► Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. Jones, M. D.; Davidson, M. G.; Keir, C. G.; Wooles, A. J.; Mahon, M. F.; Apperley, D. C. J.; Mahon, M. F.; Apperley, D. C. Dalton Dalton Transactions,Transactions, 20082008, 3655-3657, 3655-3657

recent work by matthew davidson: synthesis and structure of initiators for rop of cyclic esters

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