Category: Ionic Liquid

Application of Ionic Liquids as wearable sensors

Ionic liquids (ILs) are conductive liquids with no or little vapor pressure. ILs form dynamic structures within the liquid state, and these structures exist within an equilibrium at a specific condition. As the conditions change, either by exposure to external stimuli and environmental changes (humidity, gas composition, etc.), these materials’ conductivity also varies, thus providing materials-based sensors which can be fabricated into sensing devices.

Figure 1: a) chemical structure of allyltriphenylphosphium-bis(trifluoromethyl)sulfonyl)amide (AllylPh₃P-TFSI). B)The crystal structure of (AllylPh₃P-TFSI) shows that the phenyl rings mainly interact with the CF₃ of the TSFI anion. The anion and cation are separated, creating spaces between them. AllylPh₃P-TFSI was created mainly to accommodate the flow of ions through the channels. X-Ray structure was obtained by Dr. Damodaran Achary of the University of Pittsburgh

RoCo has been conducting ionic liquids research for many years for several applications, including batteries, carbon capture, polymer compatibilizer, and solvent. Figure 1 shows the chemical structure of allyltriphenylphosphium-bis(trifluoromethyl)sulfonyl)amide. This IL was specifically developed for gas absorption applications and studied extensively by the researchers at RoCo. On the right, single-crystal X-Ray data of this ionic liquid is shown. The IL here is different as the anion and cation are separated due to steric hindrance, forming ionic channels where polar gas molecules can reside and be used for sensor applications. This material can also be used as a high-temperature battery electrolyte as well.

There is significant interest in electronic skin sensors or wearable thin-film sensors. These sensors can be placed directly on the skin to measure body parameters such as body temperature, heartbeat, sweat composition, etc. These sensors are now used in various applications such as healthcare, sports, robotics and prosthetics, and the military. Ionic liquid-based skin sensors are an emerging type of pressure sensor capable of perceiving external stimuli of pressure, strain, and torsion and turning them into electrical signals. These ionic liquid sensors can be encapsulated in silicones and can be worn directly. When connected with smart devices, it effectively expands the ability of human beings to perceive and evaluate the external environment. It is essential to point out that ionic liquids can be polymerized and converted into membranes, coatings, thus further widening their applicability. When ionic material is impregnated into textile fibers, it can provide skin sensors with high permeability, wearable comfort, wears resistance, and anti-bacterial properties.

In the literature, several ionic liquids have been used for this application. 1-ethyl-3-methylimidazolium-tetrafluoroborate (EMIM BF₄) has been used as a gelled electrolyte in wearable electronics. In addition to EMIM BF₄, the gelled ionic liquid sensors based on a trihexyltetradecyl-phosphonium dicyanoamide have been used to evaluate real-time pH in sweat. Ionic liquid composites with carbon nanotubes and an ionic liquid ([EMIM]Tf2N) have also been used to sense surface temperature.

If you are working with ionic liquids, our knowledgeable team can support your developmental efforts by identifying the suitable ionic liquid and developing custom ionic liquid materials solutions. Contact us

Blog Materials World Ionic Liquid

Application of Ionic Liquids in Corrosion Protection

Corrosion is a multi-trillion-dollar problem:

According to the National Association of Corrosion Engineers, the global cost of corrosion is estimated to be 3.4% (or $2.5 trillion) of global GDP. These costs typically exclude aspects such as individual safety or environmental consequences. Typical corrosion protection coatings are sacrificial (coating with a second metal, e.g., zinc) or barrier polymer coating, ceramic coatings, or protection oils based on paraffinic or naphthenic mineral oils.

Polyoxometalates:

Polyoxometalates (POMs) are a large group of anionic polynuclear metal–oxo clusters with discrete and chemically modifiable structures. POM can exist in electron-rich reduced forms of different archetypes, structural flexibilities, and functionalities. POM materials have unique and potentially valuable catalytic, electronic, and magnetic material applications.

POM-IL as corrosion protection:

Streb and coworkers developed POM-based ionic liquids (POM-ILs), showing noticeable corrosion protection with self-healing properties. These POM-ILs are constituted by ammonium ions of the type (C_nH_2n+1)₄N⁺ with n = 7-8 and transition metal (TM) functionalized Keggin anions of the type [SiW₁₁O₃₉TM(H₂O)]n- with TM = Cu(II) or Fe(III) (Figure 1). Corrosion protection experiments were carried out on a copper disk drop-coated with the novel POM-ILs. The results were superior to coating with a solid POM salt and the commercially available IL 1-hexyl-3-methylimidazolium bromide (HMIM Br) (IL-0069-HP) as the reference.

Figure 1: POM-IL resulting in anti-corrosion self-healing coating. The figure above showing mixtures of POM with ammonium-based ionic liquids.

Protection against Biodeterioration and weathering:

Another type of corrosion is the corrosion of building materials (Stones, cement, and Concrete). It is a major global issue. POM-IL coatings also show significant corrosion protection on stones and building materials as well. A 2018 study shows that the use of POM-IL thin layers can protect concrete and stone from acid corrosion (“weathering”) and biofilm formation (“biodeterioration”) (Figure 2). Stone samples are coated with hydrophobic, acid-resistant POM-ILs featuring biocidal properties that resulted in better performance.

Figure 2: Images adapted from work performed by Streb 2018. The Rosemary stone was tested for acid vapor corrosion by exposing the samples to acetic acid vapor for 72 h. Sample a and b are treated with thin layer POM-ILs showing little or no acid corrosion where is C is untreated.

Our partner, IoLiTec GmBH, has tested several ionic liquids (ILs) as promising corrosion inhibitors. In this work, IoLiTec obtained optimal results with several acetate-based ILs. In addition, 1-butyl-1-methylpyrrolidinium acetate and 1- ethyl-3-methylimidazolium acetate has good corrosion protection properties. The former can be custom ordered at [email protected]. You can purchase 1-ethyl-3-methylimidazolium acetate (IL- 0189) on our website.

Figure 3: Chemical structure of the 1-butyl-1-methylpyrrolidinium acetate and 1- ethyl-3-methylimidazolium acetate also has good corrosion properties with POM.

Besides POM-based ILs, significant anti-corrosion effects can also be obtained by subtle tuning of the IL structure. For instance, applying stable bis(trifluoromethylsulfonyl)imide (BTA) anions instead of metal invasive halides can drastically improve the anti-corrosion properties and change the cation structure. RoCo can design and synthesize novel ILs to give you an innovative edge.

Contact RoCo Global today to learn more about our Research & Development Services and how we can help you exceed your goals.

Blog Materials World Ionic Liquid

Ionic Liquids: Textile recycling

Due to an increase in population and demand for fast fashion, the clothing and textile industry is the 2^nd largest polluter after the oil and gas industry. For instance, approximately 20,000 liters of water is needed to manufacture a T-shirt and a pair of jeans. The textile and clothing industry is globally 20% of total water waste. In addition, to water, United Nations Climate Change News reports that the clothing and fabric industry contributes to 10% of global GHG emissions. The EPA estimates that 17 million tons of textile products were generated in 2018, where only 14.7% was recycled, 19% was used in energy production, and the remaining 66.3% as landfill. According to EPA, the recycling rate has plateaued at 15% for the last 20 years(Figure 1). A major problem in minimizing textile waste is associated with consumer behavior and the in-availability of efficient technologies to reclaim, remake, and reuse. Polymer blends in textiles are a major challenge in achieving cost-effective recycling.

Figure 1: Textiles waste management for recycling, combustion to recover energy, and landfill

A major component in textile and fabric blends is cellulose. The traditional approaches for cellulose extraction from biomasses include the viscose and Lyocell methods. The viscose method is the most common process to extract alkali-treated cellulose using CS₂. CS₂ is an expensive, highly toxic, and volatile compound with known severe environmental impact. As a solvent, the lyocell process is based on N-methyl morpholine N-oxide (NMMO). It is prone to runaway reactions and solvent degradation leading to significant costs to generate fibers. These extraction technologies are unsuitable for fabric recycling due to their inefficiency and cost.

Reclaiming the polymers in fabrics is quite challenging. The blends of manmade materials and natural materials in textiles require unique approaches for separation. To create a truly circular economy, it is important to develop and deploy processes that can selectively separate cellulose from manmade fibers such as polyesters and nylons. This will result in a significant reduction in water, energy, and GHG emission.

Ionic liquids (ILs) have unique chemical properties such as low melting temperature (T_m < 100 ^oC), selective solubility, negligible vapor pressure, and high thermal stability (T_d > 200 ^oC). IL-based technologies are promising for the recycling of textile waste. Due to their unique properties, ILs can decrease the amount of energy and water used. Few emerging technologies have incorporated superbase and imidazolium-based ILs as an alternative to the viscose and Lyocell processes. These ILs based technologies also show potential to convert textile wastes into high-value products. Some imidazolium-based ILs (1-ethyl-3-methylimidazolium acetate) have very high cellulose solubility (>95 grams of cellulose per mole of IL).

Sixta and coworkers at Aalto University in Finland had demonstrated the upcycling of textile wastes, including 100% cotton and cotton-polyester blends, to produce pure textile-grade cellulose. In this study, the textiles wastes were dissolved in 1,5-diazabicyclo[4.3.0]non-5-enium acetate, a superbase-based ionic liquid that selectively extracts cellulose from PET blends. The team used hydraulic pressure filtration to remove the undissolved PET fraction from the 6.5 wt% cellulose solution. The resulting solution was subjected to the dry-jet wet spinning process to make textile-grade cellulose fibers to the microfiber range (0.75 to 2.95 dtex) with breaking tenacities (27 to 48 cN/tex) and elongations (7 to 9%) comparable to commercial Lyocell fibers. This technology represents an exciting route for separating cellulose from PET enabling textile recycling.

The extracted PET cannot be used in a melt spinning to make new fibers due to the degradation of its mechanical properties. The PET must be converted into high-value materials via chemical recycling and upcycling methodologies. In the literature, numerous approaches have been investigated for the chemical recycling of PET. This includes the use of cholinium acetate (Liu et al.), cholinium phosphate (Sun et al.) and 1-butyl-3-methylimidazolium acetate (Al-Sabagh et al.). 1-butyl-3-methylimidazolium hydroxide has been used to upcycle PET (Ahmed and coworkers).

Indeed, ILs, with their unique properties, open new and environmentally friendlier ways to improve chemical recycling and upcycling of textile wastes and other synthetic polymers. Even though textile recycling is a major problem, we think it can be solved by developing innovative, cost-effective, greener solutions. RoCo is here to assist you in selecting and developing environmentally friendly technology. Are you looking for an ideal partner to help you rapidly advance your research and development initiatives on capturing and using CO₂, developing high-tech functional materials, and integrating chemical recycling and upcycling using ILs? Perhaps, you want to design and test custom materials for your application? Contact RoCo Global today to learn more about our Research & Development Services and how we can help you meet, and exceed, your goals.