Living/controlled ring-opening (co)polymerization of lactones by Al-based catalysts with different sidearms
Abstract
It remains a challenging task to synthesize well-defined multi-block copolymers through the controlled/living ring-opening polymerization (ROP) of lactones without transesterification, the most common side reaction occurring during copolymerization. A series of Al-based complexes with different sidearms were prepared for living ROP of lactones such as ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) in the presence of BnOH at room temperature (RT), affording medium to high molecular weight (MW) linear polyesters with Mw up to 303 kg mol-1 and narrow molecular weight distributions (MWD, Đ as low as 1.12). The coordination-insertion polymerization mechanism was proposed based on the combination of the detailed experimental data and polymerization kinetics. It should be noted that the sidearm plays a significant important role in the reactivity of these Al-based catalyst systems. More specifically, the Al2 system with a butyl substituent on the sidearm exhibited the highest polymerization activity and the Al5 system with the bulkiest sidearm showed the lowest one among the investigated catalysts. Moreover, the Al4 system with a pyridine group on the sidearm could effectively inhibit transesterification and maintain a well-defined block copolymer structure even after heating at 50 °C for 10 h, which could also be confirmed by chain-end analyses of the produced polymers with the MALDI-TOF MS measurement.
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Tetranuclear Al complexes bearing ortho-, meta-, and para-anisidines were reported by Redshaw's group and applied in CL and rac-LA ROP.
“Tetrnuclear Al complexes bearing ortho-, meta-, and paraanisidines (Fig. 40) and their application in CL and rac-LA ROP were reported by Redshaw's group.[102]”
From Multinuclear metal catalysts in ring-opening polymerization of ε‑caprolactone and lactide: Cooperative and electronic effects between metal centers (2023) · cites this paper as [102]
The three tetranuclear Al complexes exhibited very low catalytic activity in rac-LA ROP.
“but three complexes exhibited very low cat- alytic activity in rac-LA ROP.”
From Multinuclear metal catalysts in ring-opening polymerization of ε‑caprolactone and lactide: Cooperative and electronic effects between metal centers (2023) · cites this paper as [102]
The high catalytic activity of complex 95 is attributed to the two close Me2Al bridging groups.
“The high catalytic activity of complex 95 is attributed to the two close Me 2 Al bridging groups.”
From Multinuclear metal catalysts in ring-opening polymerization of ε‑caprolactone and lactide: Cooperative and electronic effects between metal centers (2023) · cites this paper as [102]
In complex 95, the Al1-Al2 distance (3.1074(6) Å) is shorter than in complex 96 (6.4051(7) Å) and complex 97 (8.3865(14) Å).
“and Al 1 -Al 2 distance is 3.1074 (6) Å which is also shorter than these of complex 96 (6.4051 (7) Å) and complex 97 (8.3865 (14) Å).”
From Multinuclear metal catalysts in ring-opening polymerization of ε‑caprolactone and lactide: Cooperative and electronic effects between metal centers (2023) · cites this paper as [102]
Ortho-complex 95 showed poor controllability (Ð = 1.73) compared to para-complex 97 (Ð = 1.10).
“However, poor controllability of orthocomplex 95 (Ð = 1.73) was observed compared to para-complex 97 with a narrow Ð value (1.10).”
From Multinuclear metal catalysts in ring-opening polymerization of ε‑caprolactone and lactide: Cooperative and electronic effects between metal centers (2023) · cites this paper as [102]
In CL polymerization, the activity order was ortho-complex 95 > meta-complex 96 > para-complex 97.
“The activity order orthocomplex 95 > meta-complex 96 % para-complex 97 was observed in CL polymerization”
From Multinuclear metal catalysts in ring-opening polymerization of ε‑caprolactone and lactide: Cooperative and electronic effects between metal centers (2023) · cites this paper as [102]
In complex 95, the Al1-Al10 distance (2.7677(6) Å) is shorter than in complex 96 (2.8573(8) Å) and complex 97 (2.8711(12) Å).
“In complex 95, Al 1 -Al 1 0 distance is 2.7677 (6) Å which is shorter than these of complex 96 (2.8573 (8) Å) and complex 97 (2.8711 (12) Å)”
From Multinuclear metal catalysts in ring-opening polymerization of ε‑caprolactone and lactide: Cooperative and electronic effects between metal centers (2023) · cites this paper as [102]
In homo-multinuclear metal systems, if the difference between metals is not large, mononuclear polymerization and bimetallic polymerization may run in parallel to exhibit low controllability for producing polymer with unexpected molar mass and broad Ð.
“In homo-multinuclear metal systems, if the difference between metals is not large, mononuclear polymerization and bimetallic polymerization may run in parallel to exhibit low controllability for producing polymer with the unexpected molar mass and a broad Ð [70,79,82,102].”
From Multinuclear metal catalysts in ring-opening polymerization of ε‑caprolactone and lactide: Cooperative and electronic effects between metal centers (2023) · cites this paper as [102]
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References 69 · Cited by 29
- Authors
- Zhao, W., Wang, Q., Cui, Y., He, J., & Zhang, Y.
- Affiliations
- Jilin University (CN)
- Corresponding author
- Zhang, Yuetao
- Venue
- Dalton Transactions
- Publisher
- Royal Society of Chemistry (RSC)
- Published
- 2019
- Volume
- 48
- Issue
- 21
- Pages
- 7167-7178
- ISSN
- 1477-9226 (ISSN-L)
- 1477-9234
- OpenAlex
- W2901841330
- Cited by
- 29
- References
- 69
- Citations by year
- 2026: 4 · 2025: 2 · 2024: 6 · 2023: 4 · 2022: 5 · 2021: 2 · 2020: 3 · 2019: 3
- FWCI
- 0.65
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Dalton Transactions (publishedVersion)
- PubMed (publishedVersion)
- Funders
- National Natural Science Foundation of China (21422401, 21374040, 21774042, 21871107)
- Jilin University
- Topics
- Physical Sciences › Materials Science › Biomaterials › biodegradable polymer synthesis and properties
- Physical Sciences › Chemistry › Organic Chemistry › Advanced Polymer Synthesis and Characterization
- Physical Sciences › Chemical Engineering › Process Chemistry and Technology › Carbon dioxide utilization in catalysis
- Keywords
- living ring-opening polymerization, controlled ring-opening polymerization, ε-caprolactone, δ-valerolactone, coordination-insertion mechanism, block copolymers, polyesters, polymerization kinetics
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