Solid State Ionics xxx (xxxx) xxx–xxx Contents lists available at ScienceDirect Solid State Ionics journal homepage: www.elsevier.com/locate/ssi Ionic liquids in biotechnology and beyond ⁎ Johanna Claus1, Fridolin O. Sommer1, Udo Kragl Department Life, Light & Matter, Faculty for Interdisciplinary Research, University of Rostock, Albert-Einstein-Straße 25, 18059 Rostock, Germany Institute ofChemistry, Analytical and Technical Chemistry, University of Rostock, Albert-Einstein-Straße 3a, 18059 Rostock, Germany ARTICLE INFO ABSTRACT Keywords: In the past decades, ionic liquids (IL) evolved from a “designer solvent” to a well-known and well-characterized Ionic liquid class of compounds useful in reactions, extractions, and other applications. By an increasing number of syn- Polymerized ionic liquid thesized ILs also new fields of application were uncovered. The todayʼs research interest covers a range for direct Hydrogel use of ILs, application as embedding material or as catalyst. In this brief review, we present diverse applications Immobilized catalyst of pure native ILs as well as these of polymerized ionic liquids (PILs). These charged polymers unite the pre- Drug delivery sented advantages of both, ionic liquids and solid polymer structures. We also show the recent developments in the areas of drug delivery, catalysis and catalyst immobilization where these particular compositions demon- strate improvements compared to existing solutions. Besides the advantages, we likewise discuss some limita- tions and drawbacks. 1. Introduction to the diversity of anion-cation-combinations a high variety of appli- cations is possible. Table 1 summarizes selected examples, but due to The term “ionic liquid” (IL) characterizes substances which consist space restriction, this review aims to focus only on a few of them. entirely of ions, have a melting point below 100 °C and below the de- The term polymerized ionic liquids (PIL or pIL) - also named poly composition temperature a very low vapor pressure. The first IL, (ionic liquid), polymerized IL, poly(IL), IL polymer, IL derived, IL ethylammonium nitrate, has a melting point of 12 °C and was synthe- grafted or IL like - describes a polymer consisting of IL as monomeric sized by Paul Walden in 1914 [1]. Because of their versatile properties, units. Compared to conventional polymers, PILs have related properties the number of synthesized ILs and related publications has increased and possess opposed to solid electrolytes a soft character [9,10]. The rapidly especially in the last two decades. The complex correlation first PILs were described by OHNO and coworkers in 1998 [11]. The between possible hydrogen bindings, Coulomb- and van-der-Waals-in- polymerization combines the advantages of a tight polymer backbone teractions among the ions of the IL, dissolved substances and surfaces and the features of ionic liquids accomplishing a highly charged lead to multifaceted properties [2]. Compared to molecular solvents ILs polymer [12]. Widely used methods to synthesize PILs are initiated show a relatively high viscosity and density. Additionally, they have polymerizations or condensation reactions [13,14]. Another opportu- excellent solubility and miscibility properties [3]. Another interesting nity to introduce charges are post-transformation reactions of polymers characteristic is that ILs fit very well into the Hofmeister series, also [15–17]. This approach is used to synthesize organocatalysts or modify known as the lyotropic series, where a series of salts is described with chemical properties through modifications [15,16]. PILs can be cate- stabilizing effects on the solubility of proteins and their secondary and gorized by heir monomeric subunits, charge or structure (Fig. 1). Co- tertiary structure in solution [4,5]. Most of the ILs are non-flammable polymerization of different ILs, ILs with neutral monomers or the and together with their non-volatility they are often discussed as “green crosslinking of lone polymer chains results in more complex PILs than solvents” or “green alternates” to volatile organic solvents. Despite anionic, cationic or zwitterionic polymers through homo-polymeriza- these facts toxicity, biodegradability and environmental impact are tion. By polymerizing ionic liquids, the ion conductivity can be affected widely unexamined. However, it has often been pointed out that long through immobilizing anions or cations in the polymer backbone. As a alkyl chains lead to higher lipophilicity, thus higher toxicity [6,7]. result, a polymer is obtained, which only contains size specific coun- Furthermore, their very high thermal stability leads to a common de- terions due to the limitation of free space between the polymer chains composition temperature of > 350 °C. The degradation of ILs occurs [34]. regularly via Hofmann elimination or dealkylation reactions [3,8]. Due Even if the ion conductivity decrease through the decrease of free ⁎ Corresponding author. E-mail address: [email protected] (U. Kragl). 1 Both authors have contributed equally. https://doi.org/10.1016/j.ssi.2017.11.012 Received 30 September 2017; Received in revised form 15 November 2017; Accepted 18 November 2017 0167-2738/ © 2017 Elsevier B.V. All rights reserved. Please cite this article as: Claus, J., Solid State Ionics (2017), https://doi.org/10.1016/j.ssi.2017.11.012 J. Claus et al. Solid State Ionics xxx (xxxx) xxx–xxx Table 1 Possible applications of ILs. Application Example fi One-phase-system Solvent in biocatalysis • Esteri cation of 1-octanol in the presence of supercritical CO2 [24] Solvent in organic chemistry • Alkylation reactions [25] Membrane • IL was immobilized and coated by silicon in a ceramic nanofiltration module (high selectivity and stability) [26] • Pervaporation with IL ultrafiltration membrane [27] Solvent in catalysis • Catalytic olefin epoxidations with high yields in ILs [28] Stabilization and storage of cells • Storage of LB ADH in buffer solution in the presence of ILs [29] Nuclear and electrochemistry • Dealing of nuclear waste with IL for the recovery of nuclear fuel [30] Quenching • Replacement of water with IL as a new quenching medium [31] Two-phase-system Whole cell biotransformation • IL as a substrate reservoir with water as extracting agent in an multiphase system for an asymmetric reduction [32] Extraction • IL as diluents for solvent extraction of metal salts by crown ethers [33] Fig. 1. Structurally different types of polymerized ionic liquids: a) polycationic [18], b) polyanionic [19], c) zwitterionic [20], d) copolymeric [21], e) crosslinked [22] and f) complexed PILs [23]. ions, PILs exhibit promising features for a broad range of separation One attempt to increase the ion conductivity is an increased number of processes and conductive applications [10,23,35–37]. In addition to free ions. NAKAJIMA and OHNO described an enhanced conductivity fol- native ionic liquids, the polymerization of ILs reduces leakage and lowing to the addition of ILs to the polymer network. Further, this new flammability, making them attractive for application in fuel cells and network is no longer a specific conductor since free anions and cations storage devices [10]. As mentioned before, PILs allow creating specific are present [35]. conductors since one species of ion is fixed to the polymer backbone. Crosslinking the single polymer chains offers another possibility to 2 Download English Version: https://daneshyari.com/en/article/7744721 Download Persian Version: https://daneshyari.com/article/7744721 Daneshyari.com.