Unsaturated Copolyesters from Macrolactone/Norbornene: Toward Reaction Kinetics of Metathesis Copolymerization Using Ruthenium Carbene Catalysts
Unsaturated copolyesters are of great interest in polymer science due to their broad potential applications and sustainability. Copolyesters were synthesized from the ring-opening metathesis copolymerization of <i>ω</i>-6-hexadecenlactone (HDL) and norbornene (NB) using ruthenium-alkylid...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2022-04-01
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| Series: | International Journal of Molecular Sciences |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1422-0067/23/9/4521 |
| Summary: | Unsaturated copolyesters are of great interest in polymer science due to their broad potential applications and sustainability. Copolyesters were synthesized from the ring-opening metathesis copolymerization of <i>ω</i>-6-hexadecenlactone (HDL) and norbornene (NB) using ruthenium-alkylidene [Ru(Cl<sub>2</sub>)(=CHPh)(1,3-<i>bis</i>(2,4,6-trimethylphenyl)-2-imidazolidinylidene)(PCy<sub>3</sub>)] (<b>Ru1</b>), [Ru(Cl)<sub>2</sub>(=CHPh)(PCy<sub>3</sub>)<sub>2</sub>] (<b>Ru2</b>), and ruthenium-vinylidene [RuCl<sub>2</sub>(=C=CH(<i>p</i>-C<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>))(PCy<sub>3</sub>)<sub>2</sub>] (<b>Ru3</b>) catalysts, respectively, yielding HDL-NB copolymers with different ratios of the monomer HDL in the feed. The activity of <i>N</i>-heterocyclic-carbene (NHC) (<b>Ru1</b>) and phosphine (<b>Ru2</b> and <b>Ru3</b>) ligands containing ruthenium-carbene catalysts were evaluated in the synthesis of copolymer HDL-NB. The catalysts <b>Ru1</b> with an NHC ligand showed superior activity and stability over catalysts <b>Ru2</b> and <b>Ru3</b> bearing PCy<sub>3</sub> ligands. The incorporation of the monomers in the copolymers determined by <sup>1</sup>H-NMR spectroscopy was similar to that of the HDL-NB values in the feed. Experiments, at distinct monomer molar ratios, were carried out using the catalysts <b>Ru1</b>–<b>Ru3</b> to determine the copolymerization reactivity constants by applying the <i>Mayo–Lewis</i> and <i>Fineman–Ross</i> methods. The copolymer distribution under equilibrium conditions was studied by the <sup>13</sup>C NMR spectra, indicating that the copolymer HDL-NB is a gradient copolymer. The main factor determining the decrease in melting temperature is the inclusion of norbornene units, indicating that the PNB units permeate trough the HDL chains. The copolymers with different molar ratios [HDL]/[NB] have good thermal stability up to 411 °C in comparison with the homopolymer PHDL (384 °C). Further, the stress–strain measurements in tension for these copolymers depicted the appreciable increment in stress values as the NB content increases. |
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| ISSN: | 1661-6596 1422-0067 |