Title: Development of Monoselective Ion-Exchange Membranes via Layer-by-Layer Coating and Green Solvent Engineering

Objective:
The aim of this internship is to develop high-performance monoselective ion-exchange membranes using advanced layer-by-layer coating strategies, with a strong focus on blade coating techniques for scalable membrane fabrication. The project will investigate the relationship between coating parameters, polymer–solvent compatibility, and film formation to achieve thin, uniform, and reproducible selective layers. In parallel, the internship will focus on identifying and evaluating green, non-CMR solvent systems for membrane preparation using experimental screening combined with Hansen Solubility Parameter (HSP) modeling.

Background:
The CO₂ CLEANUP process is a continuous Direct Air Capture (DAC) technology that efficiently captures carbon dioxide (CO₂) from ambient air and subsequently releases it as pure CO₂ for utilization or permanent storage. The process is fully electrochemical, requiring only a salt solution and electricity. For this key enabling technology is Electrodialysis with Bipolar Membranes (EDBM).

In parallel, we are developing advanced ion-exchange membranes in-house for electro-driven separation processes. Besides conventional Cation Exchange Membranes (CEM), Anion Exchange Membranes (AEM), and Bipolar Membranes (BPM), there is increasing interest in monoselective membranes that enable selective ion transport while minimizing undesired ion crossover. Such membranes are highly relevant for next-generation electrodialysis and resource recovery applications.

The development of monoselective membranes requires the fabrication of ultrathin functional selective layers on mechanically stable membrane substrates. Achieving these thin and defect-free coatings demands precise control over coating techniques, particularly blade coating and other scalable layer-by-layer deposition methods. Parameters such as solution viscosity, polymer concentration, solvent evaporation behavior, coating speed, and wet film thickness strongly influence membrane morphology and performance.

A major challenge in membrane fabrication is solvent selection. The solvent must ensure complete polymer dissolution, compatibility with the substrate, suitable rheological behavior during coating, and controlled film formation during drying. In addition, there is a strong need to replace conventional hazardous solvents with renewable and non-CMR alternatives to improve sustainability and industrial applicability.

To address this challenge, the project will combine experimental solvent screening with Hansen Solubility Parameter (HSP) modeling to predict polymer–solvent compatibility and optimize solvent/non-solvent systems for scalable membrane fabrication.

Tasks:

• Develop monoselective membrane structures using layer-by-layer coating approaches.

• Investigate blade coating parameters for thin selective layer fabrication.

• Study the influence of coating thickness, drying behavior, and viscosity on membrane quality.

• Evaluate polymer–solvent compatibility for membrane materials using Hansen Solubility Parameters (HSP).

• Screen and evaluate renewable, non-CMR solvent systems for membrane coating.

• Optimize polymer loading (% w/w) and solution rheology for reproducible coating performance.

• Assess solvent stability and compatibility with membrane substrates.

• Characterize membrane quality in terms of uniformity, defect formation, handling properties, and reproducibility.

• Correlate solvent properties and coating conditions with membrane morphology and electrochemical performance.

• Establish scalable coating protocols suitable for future pilot-scale production.

Expected Outcome:

• Development of reproducible monoselective membrane coating protocols.

• Identification of suitable green and non-CMR solvent systems for membrane fabrication.

• Optimized blade coating conditions for ultrathin selective layers.

• Improved understanding of the relationship between solvent properties, viscosity, and film formation.

• Hansen Solubility Parameter-based guidance for solvent and non-solvent selection.

• Scalable membrane fabrication strategies for electro-driven separation technologies.

Skills to be Developed:

• Blade coating and layer-by-layer membrane fabrication techniques.

• Polymer solution preparation and rheology optimization.

• Thin-film coating process development and troubleshooting.

• Hansen Solubility Parameter (HSP) modeling for polymer–solvent interactions.

• Membrane characterization and reproducibility analysis.

• Green solvent evaluation and sustainable process development.

• Experimental planning, data analysis, and scale-up considerations.

Profile of the Student:

• Interest in polymer chemistry, membrane science, and sustainable materials.

• Interest in coating technologies and thin-film fabrication.

• Understanding of polymer–solvent interactions and solution behavior.

• Curious about combining experimental work with theoretical modeling approaches.

• Independent, analytical, and detail-oriented in laboratory work.

• Available for a minimum 4-month internship, preferably 8 months. Internship starts in September 2026

Impact:
The membranes developed in this project will contribute to advanced electro-driven separation technologies for Carbon Capture and sustainable chemical processing. The development of scalable monoselective membrane fabrication methods and greener solvent systems will support safer and more sustainable membrane manufacturing while improving ion selectivity and process efficiency in electrodialysis applications.