About the crystallization of cyclic and linear poly(L-lactide)s in alcohol-initiated and Sn(II)2-ethylhexanoate-catalyzed ROPs of L-lactide conducted in solution. (16th May 2023)

• Record Type: Journal Article
• Authors: Kricheldorf, Hans R.; Weidner, Steffen M.
• Is Part Of: Polymer. Volume 276(2023)
• Publication Date: 2023-05-16
• Subjects: Crystallization -- Cyclisation -- Lactide -- MALDI-TOF mass spectrometry -- Ring-opening polymerization; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2023.125946
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: 1-Hydroxymethylnaphtalene (HMN) or 11-bromoundecanol (BUND) were used as initiators and Sn(II) 2-ethylhexanoate (SnOct2 ) as catalyst for ROPs of L-Lactide (LA) at 115 °C in bulk or in 4 M and 2 M solutions in toluene. The LA/In ratio, the LA/Cat ratio and the time were varied. The matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF) mass spectra exclusively displayed peaks of linear chains, when the ROPs were conducted in bulk. But in contrast to reports in the literature, mixtures of linear and cyclic poly(L-lactide) (PLA), were obtained, when the ROPs were performed in solution. The intensity distribution of the mass peaks of cyclic PLAs displayed a "saw-tooth pattern" after annealing in contrast to the mass peak distribution of the liner chains. This new phenomenon indicated that cyclic PLAs and linear PLAs crystallized in separate crystals from the same reaction mixture. This conclusion was confirmed by fractionated crystallization from 2 M solution, which confirmed that the cyclic PLAs nucleate and crystallize faster than the linear chains. Graphical abstract: Image 1 Highlights: Alcohol-initiated ROPs of lactide in solution yield linear and cyclic polylactides (PLA). Cyclic and linear PLA crystallite separately from the same reaction mixture. Cyclic PLA show a "saw-tooth-pattern" in the MALDI mass spectra contrary to linear PLA.