Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - A Series of Bis(thiophosphinic amido)yttrium Initiators for Lactide Ring-Opening Polymerization
AU - Hodgson, Linda M.
AU - Platel, Rachel H.
AU - White, Andrew J. P.
AU - Williams, Charlotte K.
PY - 2008/11/25
Y1 - 2008/11/25
N2 - The syntheses of a series of bis(thiophosphinic amido) yttrium complexes are reported by the reaction of bis(thiophosphinic amine) ligands with [Y(N(SiMe3)(2))(3)]. The complexation reactions were monitored using NMR spectroscopy and one complex was characterized by single crystal X-ray crystallography. Two substitution sites on the ligand were varied, the phosphorus substiments were phenyl, isopropyl and ethoxy groups and the diamine backbones were ethylene, trans-cyclohexylene and 2,2-dimethylpropylene groups. All the new complexes were tested as initiators for the ring opening polymerization of rac-lactide. They exhibited good polymerization control, shown by the linear fits to plots of number-averaged molecular weight (M.) versus the percentage conversion, the close agreement between the theoretical and observed degree of polymerization (DP) and the moderate polydispersity index (PDI) values. They also showed very high polymerization rates (k(app) = 2.2 x 10(-4) to 1.1 x 10(-2) s(-1) at [lactide](0) = 1 M, [initiator](0) = 5 mM). The phosphorus substituents had the greatest influence over the rate, with the order of decreasing rate being isopropyl > phenyl > ethoxy. The complexes with ethoxy phosphorus substiments exerted good stereocontrol; when rac-lactide was polymerized it formed predominantly heterotactic polylactide (P-S = 0.69-0.79).
AB - The syntheses of a series of bis(thiophosphinic amido) yttrium complexes are reported by the reaction of bis(thiophosphinic amine) ligands with [Y(N(SiMe3)(2))(3)]. The complexation reactions were monitored using NMR spectroscopy and one complex was characterized by single crystal X-ray crystallography. Two substitution sites on the ligand were varied, the phosphorus substiments were phenyl, isopropyl and ethoxy groups and the diamine backbones were ethylene, trans-cyclohexylene and 2,2-dimethylpropylene groups. All the new complexes were tested as initiators for the ring opening polymerization of rac-lactide. They exhibited good polymerization control, shown by the linear fits to plots of number-averaged molecular weight (M.) versus the percentage conversion, the close agreement between the theoretical and observed degree of polymerization (DP) and the moderate polydispersity index (PDI) values. They also showed very high polymerization rates (k(app) = 2.2 x 10(-4) to 1.1 x 10(-2) s(-1) at [lactide](0) = 1 M, [initiator](0) = 5 mM). The phosphorus substituents had the greatest influence over the rate, with the order of decreasing rate being isopropyl > phenyl > ethoxy. The complexes with ethoxy phosphorus substiments exerted good stereocontrol; when rac-lactide was polymerized it formed predominantly heterotactic polylactide (P-S = 0.69-0.79).
KW - ALKYL COMPLEXES
KW - POLYESTERS
KW - CATALYSIS
KW - YTTRIUM COMPLEXES
KW - N,O MULTIDENTATE LIGANDS
KW - EPSILON-CAPROLACTONE
KW - GROUP-3 METAL-COMPLEXES
KW - DL-LACTIDE
KW - RACEMIC LACTIDE
KW - RAC-LACTIDE
U2 - 10.1021/ma8016663
DO - 10.1021/ma8016663
M3 - Journal article
VL - 41
SP - 8603
EP - 8607
JO - Macromolecules
JF - Macromolecules
SN - 0024-9297
IS - 22
ER -