Strontium Isopropoxide: A Highly Active Catalyst for the Ring‐Opening Polymerization of Lactide and Various Lactones. Issue 20 (10th September 2019)

• Record Type: Journal Article
• Authors: Bandelli, Damiano; Weber, Christine; Schubert, Ulrich S.
• Is Part Of: Macromolecular rapid communications. Volume 40:Issue 20(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-09-10
• Subjects: matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry -- polyesters -- poly(lactic acid) -- ring‐opening polymerization -- strontium; Macromolecules -- Periodicals; Polymers -- Periodicals; Chemistry -- Periodicals; 547.705
• DOI: 10.1002/marc.201900306
• Languages: English
• ISSNs: 1022-1336

Abstract

Abstract: Commercially available strontium isopropoxide represents a suitable catalyst/initiator for the ring‐opening polymerization (ROP) of lactide (LA), ε−caprolactone, δ−valerolactone, δ−caprolactone, and δ−decalactone. Well‐defined polyesters are accessible via the solution polymerization of lactide in toluene with a [LA]:[Sr] ratio of 100:1 at room temperature with or without the addition of dodecanol as coinitiator. Kinetic studies and detailed analysis by means of matrix‐assisted laser desorption ionization mass spectrometry reveal pseudo‐first‐order kinetics of the ROP as well as excellent endgroup fidelity of the polylactide (PLA) with isopropyl and dodecyl α‐endgroups. Both isopropanolate moieties as well as the coinitiator each initiate PLA chains, enabling the synthesis of PLA with tailored molar mass. The polymerization of ε−caprolactone and δ−valerolactone confirms the high catalyst activity, which causes quantitative monomer conversion after 1 min polymerization time but broad molar mass distributions. In contrast, the catalyst is well suited for the ROP of the less reactive δ−caprolactone and δ−decalactone. Although kinetic studies reveal initially bimodal molar mass distributions, polyesters with dispersity values Ð < 1.2 and unimodal molar mass distributions can be obtained at moderate to high monomer conversions. Abstract : Commercially available strontium isopropoxide represents a highly active catalyst for the ring‐opening polymerization (ROP) of lactide, which proceeds fast at room temperature in toluene with high endgroup fidelity. Polyesters from nonsubstituted lactones reveal broad molar mass distributions, whereas the ROP of substituted lactones can be well controlled.