Analysis of the surface and interfacial chemistry of polylactide (PLA) induced by low-temperature plasmas

• Applicant: Professor Dr.-Ing. Guido Grundmeier
• Subject Area: Coating and Surface Technology ; Solid State and Surface Chemistry, Material Synthesis
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 571427667

Polylactide (PLA) is a bio-based polyester that can be synthesized from biomass or agricultural raw materials. PLA has a wide range of applications, including the packaging industry, implant materials, tissue engineering, and drug delivery. In many areas of application for PLA, however, its surface energy must be increased in order to achieve good wetting and adhesion of applied functional layers. Plasma processes are particularly suitable for such functionalization. The surface modification of PLA in low-temperature plasmas depends to a large extent on the specific plasma parameters, including the choice of process gas, the type of discharge, and the selected process pressure. As part of the proposed project, the functionalization of polylactide with functional groups such as -NH2 and -COOH via a low-pressure plasma process will be analysed using in-situ spectroscopic methods. Based on the intended analytical approach, concepts for varying the functional group density will be derived. The comparative analysis of etching rate and kinetics of functionalization serves to increase the efficiency and sustainability of the processes. In a further step, the plasma-modified substrates are examined concerning the possibility of molecular derivatization. The combination of in-vacuo analysis (X-ray photoelectron spectroscopy (XPS) and in-situ analysis (infrared spectroscopic methods: PM-IRRAS or IRRAS in combination with vibrating quartz microweighing (QCM)), using complementary ex-situ analytical techniques such as time-of-flight secondary ion mass spectrometry (ToF-SIMS), ellipsometry, atomic force microscopy (AFM ), and contact angle measurements, allows the elucidation of plasma activation of PLA surfaces as well as subsequent hydrolysis and grafting processes. The project is investigating the extent to which the functionalization of PLA can be adjusted by controlling gas phase composition, particle bombardment, and particle fluence. The adhesive properties and hydrolysis kinetics can thus be derived from the surface chemistry after plasma activation.

• DFG Programme: Research Grants