Iron(<scp>ii</scp>) carboxylates and simple carboxamides: an inexpensive and modular catalyst system for the synthesis of PLLA and PLLA-PCL block copolymers

Kirchhecker, Sarah; Nguyen, Ngoc Cuong; Reichert, Stefan; Lützow, Karola; Bungu, Paul Severin Eselem; Wangelin, Axel Jacobi von; Sandl, Sebastian; Neffe, Axel T.

doi:10.1039/d3ra03112h

Cited by 2 publications

(5 citation statements)

References 88 publications

(126 reference statements)

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“…It displayed three different series with a characteristic peak-topeak distance of 144 Da, as shown in the enlarged plot, typical of the lactide repeating unit. 6 and the literature therein, 11 the peaks related to 2n + 1 series (lactic acid repeating units) resulting from transesterification.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The second series, defined by the m / z of 4053.916, is characterized by the addition of 72 Da from m / z of the first series and corresponds to the repeating addition of lactic acid and is defined by the general formula H(O 4 C 6 H 8 ) n O 2 C 3 H 4 OC 14 H 29 Na + . According to the recently published work by Kirchhecker et al ( 6 ) and the literature therein, 11 the peaks related to 2 n + 1 series (lactic acid repeating units) resulting from transesterification.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, side reactions may occur in moisture (5), producing PLA chains with acid end groups (COOH) (4b). 6 As the polymerization proceeds, the melt viscosity increases due to the increasing molar mass. This causes a decline in the polymerization rate as the monomer concentration decreases and becomes less accessible.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Aliphatic polyesters, such as poly(lactic acid) (PLA), are continuously gaining interest in biomedical applications, thanks to their ability to degrade into nontoxic metabolites (CO 2 and H 2 O). These classes of polymers are also gaining interest in academic and industrial research due to their eco-friendly properties, making them a potential replacement for traditional petroleum-based plastics used in applications such as packaging, medical implants, and drug delivery systems. − …”

Section: Introductionmentioning

confidence: 99%

“…In addition, the nonactive catalyst (1) can also be activated by water. Therefore, side reactions may occur in moisture (5) , producing PLA chains with acid end groups (COOH) (4b) . As the polymerization proceeds, the melt viscosity increases due to the increasing molar mass.…”

Section: Introductionmentioning

confidence: 99%

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Stereochemical Heterogeneity Analysis of Polylactides by Multidimensional Liquid Chromatography

Eselem Bungu,

Luetzow,

Lettau

et al. 2024

Anal. Chem.

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A new and robust high-performance liquid chromatography (HPLC) method that separates poly(lactic acid) (PLA) according to its stereochemical composition is presented. Using this method, poly(L-lactide) incorporating trace amounts of meso-lactide resulting from the racemization is separated from the pristine polymer. To prove this aspect in more detail, a representative poly(L-lactic acid) standard, assumed to be highly homogeneous, was separated using this method. The result showed that this was not the case as a fraction incorporating meso-lactide due to racemization occurring during the synthesis is separated. Employing two-dimensional liquid chromatography (2D-LC), the molar mass differences of the separated species were investigated, and fractions with similar molecular sizes were detected, confirming that the LC separation is solely based on stereochemical heterogeneity. The sample was further fractionated by preparative HPLC, followed by an in-depth analysis of the fractions using homonuclear decoupling in proton nuclear magnetic resonance ( 1 H NMR). Convincing results that unveiled significant differences in the stereochemistry of the isolated PLA fractions were obtained. Subsequent analysis by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) also confirmed oligomer series with different end group structures, indicating that the applied HPLC method is very sensitive to minor variations in stereochemistry and end groups. This integrated approach offers detailed insight into the structural characteristics of PLA polymers, contributing to a better understanding of their composition and potential applications.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%