Tailoring Bulk and Surface Composition of Polylactides for Application in Engineering of Skeletal Tissues

Ferrer, Gloria Gallego; Liedmann, Andrea; Niepel, Marcus S.; Liu, Zhen-Mei; Groth, Thomas

doi:10.1007/12_2017_26

Cited by 5 publications

(3 citation statements)

References 138 publications

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“…Application of PLLA in the biomedical sector often requires preparation of porous structures or scaffolds, for example in the fields of tissue engineering, or controlled drug delivery . Formation of scaffolds may be achieved by thermally induced phase separation (TIPS) of solvent‐rich polymer solutions, showing an upper critical solution temperature (UCST) .…”

Section: Introductionmentioning

confidence: 99%

Crystallization of poly( l ‐lactic acid) in solution with the mosquito‐repellent N , N ‐diethyl‐3‐methylbenzamide

Sungkapreecha

Iqbal

Focke

et al. 2019

Polymer Crystallization

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Poly(l‐lactic acid) (PLLA) can be used as a carrier for the mosquito repellent N,N‐diethyl‐3‐methylbenzamide (DEET). PLLA dissolves in DEET at elevated temperature and crystallizes on cooling to below the concentration‐dependent equilibrium melting temperature, leading to scaffold formation. In this work, non‐isothermal and isothermal crystallization experiments were performed, using differential scanning calorimetry and polarized‐light optical microscopy. Crystallization of PLLA in solution with DEET is faster than melt‐crystallization of neat PLLA, with the maximum crystallization rate decreasing with decreasing PLLA content in the investigated range from 5 to 50 m% PLLA. The decrease of the maximum crystallization rate with increasing solvent content is due to decreases in both the maximum crystal growth rate and the nuclei density. The observed downward shift of the temperature range of crystallization is caused by the depression of equilibrium melting temperature and a strong decrease of the glass transition temperature, both occurring with increasing solvent concentration. It is assumed that the strong decrease of the glass transition temperature due to the presence of DEET, and the related increase of the mobility of PLLA chains, is the main reason for the increased crystallization rate compared to melt‐crystallization of PLLA. It is demonstrated that a large variety of spherulitic superstructures can be obtained by variation of the crystallization conditions, presumably leading to largely different 3D scaffold structures and DEET‐delivery characteristics.

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Section: Introductionmentioning

confidence: 99%

Crystallization of poly( l ‐lactic acid) in solution with the mosquito‐repellent N , N ‐diethyl‐3‐methylbenzamide

Sungkapreecha

Iqbal

Focke

et al. 2019

Polymer Crystallization

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show abstract

“…All glassware was dried in an oven at 160 °C, prior to use. Characterization by 1 H and 13 C NMR spectra was recorded on a Bruker 400 or Bruker UltraShield 300 MHz NMR spectrometer at room temperature unless otherwise stated. 1 H NMR spectra were referenced to the residual protio-solvent resonance (δ 7.27 ppm for CDCl 3 , 7.15 ppm for C 6 D 6 and 2.08 ppm for toluene-d 8 ).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The tacticity bias (90% isotactic) in the poly( l -lactide) produced by tin octoate thus results from chain-end control instead of the preferred enantiomorphic-site control. While the polymer does find many commercial applications, its use in food contact applications or medical devices may necessitate the challenging and costly removal of the cytotoxic tin from the product itself. − …”

Section: Introductionmentioning

confidence: 99%

Lactide Polymerization Using Zinc Dichloride Complexes Containing a Neutral Bidentate Ligand with a Diacylated Cyclic Guanidine

et al. 2022

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Zinc complexes of neutral bidentate ligands that contain an electron-poor diacylated cyclic guanidine are reported, along with their reactivity in solvent-free polymerization of rac-lactide. The diacyl groups significantly decrease the electron-donating ability of the ligand compared to the corresponding nonacylated derivative. This manifested itself through restricted rotation about the formal C−N exo double bond, with the Gibbs free-energy rotational barrier (ΔG ‡) ranging from 47.4 to 59.6 kJ mol −1 . Restricted rotation was also observed for the isopropyl substituent syn to the N exo aryl ring with ΔG ‡ values of 47.5−51.9 kJ mol −1 . Coordination of the ligands to zinc caused further π-electron delocalization from the endocyclic to the exocyclic nitrogen, thereby decreasing the Wiberg bond index of the C−N exo bond from 1.67−1.70 to 1.48−1.50 and eliminating all restricted rotations at room temperature. All three complexes were active in the solvent-free polymerization of rac-lactide with the second-order polymerization rate constant for the anthranilate-based complex of 7.30 × 10 −3 M −1 s −1 . The resulting polymers had a slight heterotactic bias (P r = 0.60) with molecular weights lower than anticipated, possibly due to transesterification, as suggested by mass spectrometry. The mass spectrum of the polymer did not show evidence of the ligand dissociating from the metal during the initiation step and its incorporation into the polymer structure. The acylation of the cyclic guanidine thus imparts advantages to the ligand, with the second building block offering additional opportunities to further improve the catalytic performance of these zinc complexes.

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High molecular weight poly(l‐lactide) via ring‐opening polymerization with bismuth subsalicylate–The role of cocatalysts

Kricheldorf

Weidner

2020

J of Applied Polymer Sci

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The catalytic potential of bismuth subsalicylate (BiSub), a commercial drug, for ring‐opening polymerization of l‐lactide was explored by variation of cocatalyst and polymerization time. Various monofunctional phenols or carboxylic acids, aromatic ortho‐hydroxy acids, and diphenols were examined as potential cocatalysts. 2,2′‐Dihydroxybiphenyl proved to be the most successful cocatalyst yielding weight average molecular weights (uncorrected Mw values up to 185,000) after optimization of reaction time and temperature. Prolonged heating (>1‐2 h) depending on catalyst concentration) caused thermal degradation. In polymerization experiments with various commercial Bi(III) salts a better alternative to BiSub was not found. By means of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry a couple of unusual and unexpected transesterification reactions were discovered. Finally, the effectiveness of several antioxidants and potential catalyst poisons was explored, and triphenylphosphine was found to be an effective catalyst poison.

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Tailoring Bulk and Surface Composition of Polylactides for Application in Engineering of Skeletal Tissues

Cited by 5 publications

References 138 publications

Crystallization of poly( l ‐lactic acid) in solution with the mosquito‐repellent N , N ‐diethyl‐3‐methylbenzamide

Crystallization of poly( l ‐lactic acid) in solution with the mosquito‐repellent N , N ‐diethyl‐3‐methylbenzamide

Lactide Polymerization Using Zinc Dichloride Complexes Containing a Neutral Bidentate Ligand with a Diacylated Cyclic Guanidine

High molecular weight poly(l‐lactide) via ring‐opening polymerization with bismuth subsalicylate–The role of cocatalysts

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