Matrix-assisted laser desorption/ionisation time-of-flight characterisation of biodegradable aliphatic copolyesters

Area of Science:

• Polymer Chemistry
• Analytical Chemistry

Background:

• Biodegradable copolyesters are synthesized via high-temperature melt polycondensation.
• Characterization of these polymers is crucial for understanding their properties and degradation behavior.

Purpose of the Study:

• To structurally characterize and determine the molar mass of biodegradable copolyesters.
• To investigate the presence of cyclic and linear species and identify potential degradation products.

Main Methods:

• Matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectrometry.
• Off-line size exclusion chromatography coupled with MALDI-TOF (SEC/MALDI).

Main Results:

• MALDI-TOF spectra revealed expected linear species and unexpected linear species with olefin and carboxyl end groups, indicating thermal degradation.
• SEC-MALDI determined absolute average molar masses, which were significantly lower than those calculated using polystyrene standards.
• Analysis of SEC fractions confirmed the presence of both linear and cyclic oligomers, enabling simultaneous molar mass determination.

Conclusions:

• The study identified thermal degradation as a significant side reaction during melt polycondensation of copolyesters.
• SEC-MALDI provides a more accurate method for molar mass determination of copolyesters compared to traditional SEC with polymer standards.
• The methodology allows for the differentiation and quantification of cyclic and linear species in polymer samples.