Neodymium‐based catalysts bearing phosphate ligands for ring‐opening polymerization of ɛ‐caprolactone

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Abstract
Neodymium‐based catalysts coordinated with phosphate ligands (NdCl3·3L), where L = triethyl phosphate (TEP) or tris(2‐ethylhexyl) phosphate (TEHP), were synthesized. The ring‐opening polymerizations (ROP) of ɛ‐caprolactone (ɛ‐CL) with these catalysts in the presence of benzyl alcohol initiator were performed, yielding polymers with well‐defined molecular weights and relatively narrow polydispersity index (PDI = 1.22–1.65). In situ NMR analysis of the reaction between NdCl3·3TEP and benzyl alcohol indicated that ROP proceeds through a coordination‐insertion mechanism. The end groups of the resultant polymers were determined using MALDI‐ToF mass spectrometry and NMR spectroscopy. The quasi‐living nature of this catalytic system was demonstrated by kinetic studies and the successful synthesis of the block copolymer poly(ɛ‐caprolactone)‐block‐poly(l‐lactide) by sequential monomer addition. Kinetic studies revealed that the catalyst with the bulkier TEHP ligand increased the rate of ROP of ɛ‐CL as compared to the TEP ligand. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1289–1296
Funding Information
  • National Science Foundation (CHE‐1566059)
  • Welch Foundation (AT‐1740)

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