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Cited by 470

The DOI matches its Crossref record; 5 of the 5 references it cites were found in a registry or an index.

Polymerization of l,l-Lactide Initiated by Aluminum Isopropoxide Trimer or Tetramer

Kowalski, Adam, Duda, Andrzej, Penczek, Stanislaw·1998·Macromolecules
DOI 10.1021/ma971737k
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Abstract

Kinetics of polymerization of l, l -lactide (LA) initiated with aluminum isopropoxide (Al(O i Pr) 3 ) trimer (A 3 ) or tetramer (A 4 ) was followed by polarimetry and by gel permeation chromatography (GPC). Results of the kinetic measurements show that A 3 and A 4 react with LA with different rates; namely, the k i(A 3 ) / k i(A 4 ) ratios (where k i(A 3 ) and k i(A 4 ) denote the rate constants of initiation with A 3 and A 4, respectively) determined at 20, 50, 80 (THF solvent), and 120 °C (dioxane-1,4 solvent), are equal to 2.8 × 10 3, 8.0 × 10 2, 2.9 × 10 2, and 1.1 × 10 2, respectively. Direct observations of the A 3 /LA and A 4 /LA reacting mixtures by means of 13 C NMR spectroscopy confirm this large difference of A 3 and A 4 reactivities in their reactions with LA. Initiation with A 4 is slow enough to give polymerization that is less under control, in comparison with that initiated by A 3 alone. However, due to the relatively low rate of propagation, in comparison with that of the A 4 → A 3 transformation, the apparent rates of LA polymerization initiated with A 3 or A 4 tend to converge, particularly at higher monomer conversion degrees (>90 mol %) and at higher temperatures, suggesting that also the less reactive A 4 is eventually transformed into the tris(macroalkoxide) ((...−C(O)CH(CH 3 )O) 3 Al) growing species almost completely. Molecular weight ( M̄ n ), polydispersity index ( M̄ w / M̄ n ), and kinetic measurements of the A 3 -initiated LA polymerization reveal a living character of this process: initiation is fast and quantitative, each −O i Pr group of A 3 starts growth of one macromolecule, and the concentration of the resulting active centers remains constant. On the other hand, propagation exhibits fractional order (e.g., equal to 0.7 at 80 °C in THF solvent) in active centers. Therefore, kinetic data were analyzed by assuming that the actually propagating active species (P n *) aggregate reversibly into the unreactive dimers.

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Metadata

Authors
Kowalski, A., Duda, A., & Penczek, S.
Venue
Macromolecules
Publisher
American Chemical Society (ACS)
Published
1998-03-15
Volume
31
Issue
7
Pages
2114-2122
ISSN
  • 0024-9297 (ISSN-L)
  • 1520-5835
DOI
10.1021/ma971737k
OpenAlex
W1977865120
Cited by
470
References
5
FWCI
4.88
Type
journal article
Language
en
Open access
closed

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CoChat. (2026). Citation check: Polymerization of l,l-Lactide Initiated by Aluminum Isopropoxide Trimer or Tetramer. https://app.cochat.ai/papers/10.1021/ma971737k
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Kowalski, A., Duda, A., & Penczek, S. (1998). Polymerization of l,l-Lactide Initiated by Aluminum Isopropoxide Trimer or Tetramer. Macromolecules. https://doi.org/10.1021/ma971737k

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