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This research investigates the enzymatic degradation of polyester films using in-situ ATR-FTIR spectroscopy.

July 13, 2026Open Access

Enzymatic Degradation of Thin Polyester Films Studied by In-situ ATR-FTIR Spectroscopy

MMM. MüllerLeibniz Institute of Polymer Research NSN. SudarsanLeibniz Institute of Polymer Research BUB. UrbanLeibniz Institute of Polymer Research

Key Points

This research investigates the enzymatic degradation of polyester films using in-situ ATR-FTIR spectroscopy.
Thin and thick polyester films were created from PET and PBT solutions and analyzed with in-situ ATR-FTIR spectroscopy.
Films were treated with Is PETase and LCC-iccg at different temperatures to assess degradation.
Complementary techniques included ellipsometry, spectroscopic reflectometry, and scanning force microscopy for detailed analysis.
Is PETase showed significantly higher degradation rates of PET films at 30 °C, compared to LCC-iccg at 60 °C.
PBT films exhibited minimal degradation except under LCC-iccg at 60 °C, resulting in significant polymer loss.
SFM revealed changes in surface morphology, indicating varying levels of degradation across treatments.

Abstract

Abstract The increasing presence of micro- and nanoplastics in the environment underscores the need for effective polymer degradation strategies and related analytics. Here we present model studies on the enzymatic degradation of polyester materials relevant for environmental protection and recycling using ATR-FTIR spectroscopy. Thin (45–59 nm) and thick (92–113 nm) poly(ethyleneterephthalate) (PET) and poly(butyleneterephthalate) (PBT) films were deposited onto silicon (Si) internal reflection elements (IRE) by spin coating or rolling from trifluoroacetic acid (TFA) solutions and annealing at 200 °C. Films were exposed to borate buffered solutions of Is PETase at 30 °C or LCC-iccg at 30 °C and 60 °C. In-situ ATR-FTIR spectroscopy was applied to monitor enzymatic degradation of the films on a molecular level complemented by ellipsometry, spectroscopic reflectometry (SR) and scanning force microscopy (SFM). Thin and thick PET and PBT films showed surface integrity in buffer at 30 °C, while only PBT and thick PET films remained stable at 60 °C. Significantly, diagnostic IR bands of PET showed decreasing intensities after contact with buffered solutions of either Is PETase at 30 °C or LCC-iccg at 30 °C and 60 °C enabling extraction of degradation amplitudes and apparent kinetic constants. Both enzymes showed different degradation kinetics: Is PETase displayed significantly higher amplitude and apparent kinetic constants of PET film degradation at 30 °C, whereas LCC-iccg at 60 °C on thick PET films exceeded even those for Is PETase at 30 °C. PBT films showed no substantial degradation except under LCC-iccg at 60 °C where a considerable polymer amount was degraded. Ellipsometry and SR data on enzymatically degraded PET and PBT film were in line with the ATR-FTIR data. SFM images of thin PET films revealed featureless granular morphologies before and a grinded texture of the silicon substrate after Is PETase treatment indicative of increased degradation, whereas, thin PBT films indicated low degradation and conserved fibrillar structures after IsPETase treatment. Keywords: enzymatic polymer degradation, PETase, polyester film, poly(ethyleneterephthalate), poly(butyleneterephthalate), in-situATR-FTIR spectroscopy

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