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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 3 - NAPOLI (Nanoporous Asymmetric Poly(Ionic Liquid) Membrane)

Teaser

Summary

- What is the problem /issue being addressed?

The NAPOLI project aims atsynthesis and materials application of nanoporous gradient polymer membranes of high charge density, which are an innovative type of porous polymer membranes that are missing in and will complement the state-of-the-art membrane technology. In such membranes, the combination of nanopore confinement and charges of high density, plus the flexibility in surface chemistry design, will be superimposed with a gradient property profile (such as composition gradient, pore size gradient, filler gradient, etc.) across the membrane, which creates a previously non-accessible physicochemical environment entirely different from that in conventional porous polymer membranes. Unknown diffusion and transportation phenomena are expected to be identified, and their applications in and beyond traditional filtration membranes, such as actuators, sensors and antibacterial coatings, will be studied. So far, these membranes have been rarely investigated systematically due to difficulties associated with their limited accessability that retards the progress of their research. The NAPOLI project will break through the synthetic barrier for such membrane structures and provides researchers easy access to nanoporous gradient ionic membranes. Some fundamental physical properties, and their applications as environmental sensors and energy utilization will also be part of this project.

-Why is it important for society?

With the rapid growth of our population on earth, accommodate more than 9 billion people around 2050, there will be a huge demand for enough energy and clean environment. The current status of energy and environmental technology will not meet that need, and we are under pressure to develop more efficient functional materials to address these issues. Membrane technology is one of the key battle fields that can mitigate such issues. Broadening the structure scope of membranes, expanding their application spectrum, and understand physics and chemistry occurring in uniquely (nano)structured membranes, are necessarily needed and encouraged. The project will above all bring new knowledge and technology to the current membrane research by providing nanoporous gradient poly(ionic liquid) membranes, and in additional promotes further development of new membrane-derived devices that can help address crisis in energy and environmental fields in our society in the near future.

- What are the overall objectives?

The overall objects are to 1) produce a library of (nano)porous gradient ionic polymer membranes that are not accessible in a large scale and size previously, 2) to understand and approach basic physicochemical properties of such membranes, which will serve as a roadmap to guide researchers entering this field in the near future, 3) realize primary application models of such membranes in and beyond filtration membranes, especially in the environment (sensors, sorbent, etc.) and energy (ion separation, clean water production, desalination, etc.) areas. The project in parallel targets the training of young researchers in EU to pave their way to the frontiers of the state-of-the-art membrane science and technology.

Work performed

1) From the project beginning till now, the team has fully understood the formation mechanism of the nanoporous gradient poly(ionic liquid) membranes produced by treatment of a poly(ionic liquid)/poly(acrylic acid) blend film with an aqueous ammonia solution. This mechanism has not been so clear to us before the ERC Starting project. The understanding of the membrane formation mechanism helps significantly the expansion of the structure library of porous gradient ionic membranes, and it also inspires us to fabricate nanoporous gradient polymer membranes by other synthetic tools.

2) In addition, a systematic investigation of a variety of experimental parameters has been conducted in the project so far, which has enabled the access of a big pool of different NAPOLI structures, and improved the structural stability and sustainability of such membranes. Via optimization and new synthetic tools, the cost to produce such membranes on a large size has been massively reduced. For example, a new fabrication method by photochemistry that we have proposed in our DoA has been developed now to fabricate an entirely new group of NAPOLI membranes.

3) Along with the rapid progress in synthesis of new porous gradient ionic membranes, we have pushed forward the technological use of such membranes, from the initial detection of organic solvents to the sensing of toxic gas, such as ammonia in a gas state, the weak acids in aqueous solutions, and H2O2 in a buffer solution. Our latest breakthrough is to use NAPOLI membranes as template to fabricate hybrid nanoporous metal organic framework/poly(ionic liquid) membranes and porous nitrogen-doped carbon membranes, which have tremendous potential in electrocatalysis and sensing.

4) Via collaboration with other groups, we have deepened our understanding of physicochemistry of poly(ionic liquid)s. For example, the ion conduction in bulk poly(ionic liquid), their interaction with CO2, the effect of cation structures on their metal ion uptake behavior, etc. These knowledge sets a firm base for the next stage investigation of poly(ionic liquid) in NAPOLI membranes.

Final results

1) The structure complexity of NAPOLI membrane has reached an unprecedentedly level well beyond the state of the art. For example, we realized 2 coexistent structural gradient elements (cross-linking density, pore size, chemical composition, etc.) along the membrane cross-section. These previously inaccessible structures have opened up a window to explore a wide range of materials applications, especially in sensing external environment and reacting with chemical stimuli.
2) One of our nanoporous poly(ionic liquid)/metal organic framework mixed gradient membranes has exhibited capability to detect ammonia in air of low concentration, which represents a new way to detect toxic ammonia gas around us. Along this directions, we expect to invent several new types of sensors, e.g. for indoor gas control or for detection of additives in food industry by the end of this project.
3) by using a commercial cotton cloth as template, we prepared a hybrid NAPOLI/cotton cloth actuator, which can rotate among water wetting. A prototype generator based on the rotating of such membranes coupled with Cu metal wires has been used to sense wet environment by producing an electronic signal of very high open voltage.