Organocatalyzed ring-opening polymerization of cyclic butylene terephthalate oligomers
Résumé
In this study, various organic compounds, with different activation modes, have been tested as catalysts for the ring-opening polymerization (ROP) of cyclic butylene terephthalate oligomers (CBT) in bulk at 210 °C, using tert-butylbenzyl alcohol (tBnOH) as initiator. Among them, 1,3,5-triazabicyclo[4.4.0]dec-5-ene (TBD) appeared to be the most efficient, achieving high monomer conversions in short reaction times (within minutes). Analysis by size-exclusion chromatography (SEC) of the poly(butylene terephthalate) (PBT) synthesized using this catalyst also showed that the polymerization follows the expected theoretical Mn trend for molecular weights up to 50 kg·mol−1. Chain-end fidelity relatively to the alcohol initiator has been confirmed by MALDI-TOF mass spectroscopy, which showed that all polymer chains possess the tert-butylbenzyl moiety as chain-end. Finally, to demonstrate the potential of this system for the synthesis of PBT-based block copolymers, a monomethyl ether poly(ethylene glycol) (PEG) of 5000 g·mol−1 has been employed as initiator for the ROP of CBT. A PEO-b-PBT block copolymer of 15,000 g·mol−1 could thus been obtained, as confirmed by the shift of the SEC traces towards higher molecular weights and the same diffusion coefficient determined for 1H NMR signals of the PEO block and the PBT block.