Comparative Analysis of Amorphous and Biodegradable Copolymers: A Molecular Dynamics Study Using a Multi-Technique Approach

Comparative Analysis of Amorphous and Biodegradable Copolymers: A Molecular Dynamics Study Using a Multi-Technique Approach

We investigate the molecular dynamics of glycolide/lactide/caprolactone (Gly/Lac/Cap) copolymers using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), <sup>1</sup>H second-moment, <sup>1</sup>H spin-lattice relaxation time (T<sub>...

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Bibliographic Details
Main Authors: Alovidin Nazirov, Jacek Klinowski, John Nobleman
Format: Article
Language:English
Published: MDPI AG 2025-03-01
Series:Molecules
Subjects:
glycolide
lactide
caprolactone
biopolymer
molecular dynamics
relaxation spectroscopy
Online Access:https://www.mdpi.com/1420-3049/30/5/1175
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Summary:We investigate the molecular dynamics of glycolide/lactide/caprolactone (Gly/Lac/Cap) copolymers using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), <sup>1</sup>H second-moment, <sup>1</sup>H spin-lattice relaxation time (T<sub>1</sub>) analysis, and <sup>13</sup>C solid-state NMR over a temperature range of 100–413 K. Activation energies and correlation times of the biopolymer chains were determined. At low temperatures, relaxation is governed by the anisotropic threefold reorientation of methyl (-CH<sub>3</sub>) groups in lactide. A notable change in T<sub>1</sub> at ~270 K and 294 K suggests a transition in amorphous phase mobility due to translational diffusion, while a second relaxation minimum (222–312 K) is linked to CH<sub>2</sub> group dynamics influenced by caprolactone. The activation energy increases from 5.9 kJ/mol (methyl motion) to 22–33 kJ/mol (segmental motion) as the caprolactone content rises, enhancing the molecular mobility. Conversely, lactide restricts motion by limiting rotational freedom, thereby slowing global dynamics. DSC confirms that increasing ε-caprolactone lowers the glass transition temperature, whereas higher glycolide and lactide content raises it. The onset temperature of main-chain molecular motion varies with the composition, with greater ε-caprolactone content enhancing flexibility. These findings highlight the role of composition in tuning relaxation behavior and molecular mobility in copolymers.
ISSN:1420-3049

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