Determination of thermal transitions in polyesters by temperature-dependent FTIR spectroscopy
Abstract
Temperature-dependent Fourier Transform Infrared Spectroscopy (FTIR-T) was employed to characterize thermal transitions in four semicrystalline biodegradable polyesters, poly(ε-caprolactone) (PCL), poly(butylene succinate) (PBS), poly(L-lactic acid) (PLLA), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and compared with Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The carbonyl stretching vibration (νC=O) was monitored relative to a temperature-insensitive methylene deformation band (δCH2) using two metrics: a wavenumber ratio reflecting dipolar coupling changes and an intensity ratio strongly influenced by thermo-mechanical softening and interfacial penetration into the ATR crystal. FTIR-T detected the melting transition in all polymers, with derivative maxima at 62-63 °C for PCL, 119-120 °C for PBS, 173 °C for PLLA, and 185-186 °C for PHBV, closely matching the DSC melting peaks (62.3, 116.4, 174.1, and 175.8 °C, respectively). Wavenumber variations were consistent with structural disordering in PCL, PBS and PHBV, whereas PLLA exhibited negligible frequency shifts, suggesting limited changes in the local dipolar environment even near melting. Intensity changes increased sharply near melting and correlated with drops of several orders of magnitude in complex viscosity measured by DMA, supporting a predominantly thermo-mechanical contribution to the observed intensity variations. FTIR-T thus complements DSC by providing information consistent with molecular reorganization and interfacial rheological changes during polymer thermal transitions.
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BibTeX
@article{jourdainne2026determination,
title = {{Determination of thermal transitions in polyesters by temperature-dependent FTIR spectroscopy}},
author = {Nathan Jourdainne and Rebeca Heller dos Santos and Sébastien Gaucel and Nicolas Sbirrazzuoli and Stéphane Peyron and Chahinez Aouf and Nathanael Guigo},
journal = {Polymer Testing},
year = {2026},
month = oct,
doi = {10.1016/j.polymertesting.2026.109267},
url = {https://hal.inrae.fr/hal-05836729v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Determination of thermal transitions in polyesters by temperature-dependent FTIR spectroscopy
AU - Nathan Jourdainne
AU - Rebeca Heller dos Santos
AU - Sébastien Gaucel
AU - Nicolas Sbirrazzuoli
AU - Stéphane Peyron
AU - Chahinez Aouf
AU - Nathanael Guigo
PY - 2026
DA - 2026/10/23
JO - Polymer Testing
DO - 10.1016/j.polymertesting.2026.109267
UR - https://hal.inrae.fr/hal-05836729v1
AB - Temperature-dependent Fourier Transform Infrared Spectroscopy (FTIR-T) was employed to characterize thermal transitions in four semicrystalline biodegradable polyesters, poly(ε-caprolactone) (PCL), poly(butylene succinate) (PBS), poly(L-lactic acid) (PLLA), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and compared with Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The carbonyl stretching vibration (νC=O) was monitored relative to a temperature-insensitive methylene deformation band (δCH2) using two metrics: a wavenumber ratio reflecting dipolar coupling changes and an intensity ratio strongly influenced by thermo-mechanical softening and interfacial penetration into the ATR crystal. FTIR-T detected the melting transition in all polymers, with derivative maxima at 62-63 °C for PCL, 119-120 °C for PBS, 173 °C for PLLA, and 185-186 °C for PHBV, closely matching the DSC melting peaks (62.3, 116.4, 174.1, and 175.8 °C, respectively). Wavenumber variations were consistent with structural disordering in PCL, PBS and PHBV, whereas PLLA exhibited negligible frequency shifts, suggesting limited changes in the local dipolar environment even near melting. Intensity changes increased sharply near melting and correlated with drops of several orders of magnitude in complex viscosity measured by DMA, supporting a predominantly thermo-mechanical contribution to the observed intensity variations. FTIR-T thus complements DSC by providing information consistent with molecular reorganization and interfacial rheological changes during polymer thermal transitions.
SN - 0142-9418
ER -