We gratefully acknowledge support from the grant, ERC-2012-StG_20111012 FOLDHALO (Grant Agreement no. 307108).

Note: Reactions were carried out in oven-dried glassware under nitrogen atmosphere. Please follow the safety measures described in the MSDS of each chemical.
1. Synthesis of 1-Alkyl-3-methylimidazolium Iodide Salts (1-m, Figure 3)
<ol>
	<li>In a three-necked, round-bottomed flask equipped with a reflux condenser fitted with a nitrogen inlet, a thermometer, a magnetic stirring bar, and a heating oil bath, dissolve 1.5 g (0.018 mol, 1 equiv) of freshly distilled 1-methyl-imidazole and 1.3 equiv of the 1-iodoalkane (chain length from C2 to C12) in 10 mL of acetonitrile.</li>
	<li>Heat the reaction mixture to reflux (75 - 80 &#176;C internal temperature) overnight under nitrogen atmosphere and then cool the mixture down to room temperature.</li>
	<li>Remove the volatile materials from the resulting mixture under reduced pressure at 50 &#176;C, using a rotatory evaporator. 
	NOTE: Imidazolium salts are highly hygroscopic and they quickly absorb water from the air. Thus, it is recommended to store them in a desiccator until use.</li>
</ol>
2. Synthesis of 1-m &#8226; 2-n XB Complexes
<ol>
	<li>Procedure 1: From solution (only for 1-2 &#8226; 2-8 in Figure 1)
	<ol>
		<li>Prepare a solution of the 1-ethyl-3-methylimidazolium iodide (1-2, MW = 238.07 g/mol) by dissolving 50 mg (0.21 mmol, 1 equiv) of 1-2 in 0.5 mL of acetonitrile.</li>
		<li>Prepare a solution of the perfluorooctyl iodide (2-8, MW = 545.96 g/mol) by dissolving 229 mg (0.42 mmol, 2 equiv) of 2-8 in 0.5 mL of acetonitrile.</li>
		<li>Mix the two solutions in a vial and keep the vial in a jar filled with paraffin oil.</li>
		<li>Let the solvent diffuse slowly in the paraffin oil at room temperature. After a period ranging from 3 to 7 days, good-quality single crystals suitable for X-ray diffraction analysis were obtained.</li>
	</ol>
	</li>
	<li>Procedure 2: Melt methodology 
	NOTE: This methodology requires an air-sealed system to mitigate against the volatility of the iodoperfluoroalkanes.
	<ol>
		<li>Mix each 1-alkyl-3-methylimidazolium iodide (1-m) with the appropriate iodoperfluoroalkanes (2-n) in a 1:2 molar ratio in a clear borosilicate glass vial equipped with a magnetic stirring bar.</li>
		<li>Close the vial and put it into an oil bath under vigorous stirring.</li>
		<li>Heat at 70 &#176;C using a hot plate for 15 min then cool the mixture down to room temperature.</li>
	</ol>
	</li>
</ol>
3. 1H and 19F NMR Experiments
NOTE: 1H NMR and 19F NMR spectra were recorded at 25 &#176;C on a NMR spectrometer operating at 499.78 MHz for 1H and 470.21 MHz for 19F, and using CDCl3 as the solvent. TMS and CFCl3 were used as internal standards for calibrating the chemical shifts in 1H NMR and 19F NMR, respectively. Bis-(2,2,2-trifluoroethyl) ether that contains both hydrogen and fluorine nuclei, was used as internal standard for establishing the ratio between 1-m and 2-n in the cocrystals.
<ol>
	<li>Preparation of the sample for NMR analysis and spectra calibration
	<ol>
		<li>Dissolve about 10 mg of each complex 1-m &#8226; 2-n in 0.5 mL of CDCl3.</li>
		<li>Add 1 &#181;L of 2,2,2-trifluoroethyl ether using a micropipette.</li>
		<li>Lock the sample, set the acquisition parameters as reported in Table 1, and record 1H and 19F NMR consecutive spectra, without removing the NMR tube from the magnet, in order to operate under the same operating conditions.</li>
		<li>Calibrate the integration parameters so that in the 1H NMR spectra the CH2O quartet of bis(2,2,2-trifluoroethyl) ether (&#948; = 4.3 ppm) corresponds to four, and in the 19F NMR spectra the CF3 triplet (&#948; = &#8722;74.5 ppm) of 2,2,2-trifluoroethyl ether corresponds to six.</li>
		<li>Calculate the ratio of the -CF2-I signal area deriving from 2-n (&#948; = &#8722;61.2 ppm in the 19F NMR spectra) and the -CH3 signal area deriving from 1-m (&#948; &#8776; 4.0 ppm in the 1H NMR spectra), in order to evaluate the ratio between 2-n and 1-m in each complex.</li>
	</ol>
	</li>
</ol>
4. Preparation of the Sample for Hot Stage Polarized Optical Microscopy (POM)
<ol>
	<li>Prepare a thin layer of the sample by placing a spatula tip amount of the supramolecular complex 1-m&#8226; 2-n between two micro cover glasses (18 mm x 18 mm).</li>
	<li>Place the sample in the hot stage between two crossed polarizers, and heat the sample to melt.</li>
	<li>Submit the sample to repeated heating/cooling cycles in order to promote phase transitions. Crystalline and liquid crystalline phases will interact with polarized light leading to brightness and color gradient, while the isotropic phase will appear dark.</li>
</ol>

The authors have nothing to disclose.

We have reported an easy and versatile protocol for the synthesis of XB fluorinated ILCs in which mesomorphicity is driven by the supramolecular anions [CnF2n+1-I&#8729;&#8729;&#8729;I&#8729;&#8729;&#8729;I-CnF2n+1]-.
It is well-established that ionic liquids based on 1-alkyl-3-methylimidazolium salts can exhibit liquid crystalline behavior. However, whatever the anion, no mesophases were observed for compounds with alkyl chains shorter than 12 carbon atoms. Therefore, the most striking aspect of the reported materials is that it is the anisotropy of the XB anion that determines mesophase formation. In fact, the strict geometrical constraints of XB impose that the intermolecular interaction occurs along the extension of the C-I bond, at the sigma hole, with angles close to 180&#176;. The iodide anions act as bidentate XB acceptors, binding two perfluorinated modules that show linear arrangement around the central iodide anion. Moreover, the fact that perfluoroalkyl chains are stiffer than equivalent HC chains, and adopt a twisted helical structure due to repulsion between 1,3-disposed CF2 groups9,52, further contributes to the generation of rigid, rod-like superanions.
This perfectly agrees with the observation that complexes containing the iodoperfluorodecane (2-10) show transition temperatures higher than those containing the iodoperfluorooctane (2-8) as the former is more anisotropic. Furthermore, the known tendency45,53 of fluoroalkanes to pack into lamellar phases determines the obtainment of SmB and SmA phases.
The superfluorinated ILCs reported in this paper demonstrate for the first time the application of the XB in the construction of ILCs based on imidazolium salts. Thanks to an accurate supramolecular design based on the high directionality of the XB and the fluorophobic effect, it is possible to obtain enantiotropic liquid crystals based on a rigid, non-aromatic, XB supramolecular synthon as the mesogenic core. The liquid crystalline behavior is independent from the length of the alkyl chains.
The supramolecular approach presented here represents an attractive platform for the design of new liquid crystalline materials and can provide new opportunities for the development of sophisticated functional materials such as room temperature ionic conductors, photoresponsive ILCs, and liquid crystalline electrolytes for application in energy devices.

Intermolecular interactions play a very important role in determining physical and chemical properties of bulk materials. When a new interaction becomes available, new structures, namely, new functions, become available. Therefore, exploring novel, specific non-covalent interactions underlying an intermolecular recognition process may open new perspectives in different fields such as materials sciences, catalysis, drug design, supramolecular chemistry, and crystal engineering. This was the case for the XB that recently became a routine tool for controlling aggregation and self-assembly phenomena1,2,3,4,5.
According to the IUPAC definition6: &#34;A halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity.&#34; A schematic representation of the XB is given in Figure 1, where X is the electrophilic halogen atom (Lewis acid, XB donor) and Y is a donor of electron density (Lewis base, XB acceptor).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/55636/55636fig1.jpg" /> 
Figure 1: Schematic representation of the halogen bond. 
The electrophilic halogen atoms (XB-donors) are covalently linked to a wide variety of molecular scaffolds (R), while the XB-acceptors (Y) can be neutral or anionic species. This figure has been reprinted from reference2. <a href="//cloudflare.jove.com/files/ftp_upload/55636/55636fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
At first sight, it may seem that this definition tackles somewhat puzzling aspects, since halogen atoms, because of their high electronegativity, are typically considered as sites of high electron density. However, the behavior of halogen atoms as electrophiles is quite general and has been elegantly rationalized by Politzer et al. with the introduction of the &#34;&#963;-hole&#34; concept7.
When a halogen atom is involved in a covalent bond, an electron redistribution occurs and the electronic density becomes anisotropic8,9,10,11. The shape of the atom becomes oblate and a region of positive electrostatic potential (the so-called &#963;-hole) develops along the extension of the covalent bond, on the outermost surface of the halogen atom (Figure 2A). This positive region is surrounded by a belt of negative electrostatic potential, orthogonal to the covalent bond. This model seems to solve the &#34;enigma&#34; of the XB since it explains the non-covalent interaction pattern of covalently-bonded halogen atoms, and the associated directional preferences, i.e., linear interactions with nucleophiles and lateral interactions with electrophiles.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/55636/55636fig2.jpg" /> 
Figure 2: Anisotropic distribution of electron density around halogen atoms. (A) Schematic representation of the anisotropic distribution of the electron density around covalently bound halogen atoms and the pattern of the resulting interactions. (B) Molecular electrostatic potential maps at the isodensity surface with 0.001 au for CF4, CF3Cl, CF3Br, and CF3I. Color ranges: red, greater than 27 kcal/mol; yellow, between 20 and 14 kcal/mol; green, between 12 and 6 kcal/mol; blue, negative. This figure has been modified from reference2. <a href="//cloudflare.jove.com/files/ftp_upload/55636/55636fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
XB has rapidly grown from a scientific curiosity to one of the most interesting noncovalent interactions in designing functional supramolecular materials12,13,14,15,16, thanks to its unique features, i.e., high directionality, tunable interaction strength, hydrophobicity, and donor atom dimensions1. The high directionality of XB can be easily understood by considering the focused nature of the &#963;-hole, while the interaction strength frequently correlates to the magnitude of the &#963;-hole. Both the size (the spatial range) and the magnitude (the value of the maximum electrostatic potential VS,max) of the &#963;-hole are affected by the polarizability and electronegativity of the halogen atom and the electron-withdrawing ability of the substituents in the neighborhood of the halogen17 (Figure 2B). As a general trend, as the halogen atom becomes more polarizable and the substituents on the molecule become more electron-withdrawing, the halogen &#963;-hole becomes more positive. Therefore, for a given R, VS,max increases in the order F &#60; Cl &#60; Br &#60; I, namely it increases with the halogen atom polarizability and decreases with its electronegativity. For a given halogen, VS,max becomes more positive when the electron-withdrawing ability of R is increased. Therefore, haloperfluorocarbons, specifically iodo-perfluoroalkanes and arenes, can act as powerful XB-donors forming particularly strong interactions18,19,20 and particularly hydrophobic adducts.
A case of PFC-HC self-assembly to give cocrystals has been reported in the late 1990s21. Upon mixing equimolar amounts of 1,2-diiodotetrafluoroethane and N,N,N&#39;,N&#39;-tetramethyl-ethylenediamine in chloroform, a supramolecular complex was isolated as white crystals stable in air at room temperature. Single crystal X-ray analysis revealed that the two components alternate in a 1-dimentional (1D) infinite chain and the interaction between the nitrogen and iodine atoms is largely responsible for keeping the perfluorinated bis-iodide in place. This proved that the nitrogen-iodine XB interaction is strong enough to overcome the low affinity existing between PFC and HC compounds and suggested that XB can be successfully exploited as an easy route to introduce fluorinated moieties into any new supramolecular materials22,23,24, including liquid crystalline materials.
Fluorinated substituents, in fact, have been successfully incorporated into liquid crystalline molecules because of the excellent stability that is offered by the C-F bond as well as the small size and the low polarizability of the fluorine atom, which gives rise to very low intermolecular dispersion interactions25,26,27. Moreover the segregation occurring between PFC and HC chains allowed control over supramolecular liquid-crystalline phases, enhancing the smectic character of a mesomorphic material28,29,30. It is generally understood that both the physical/chemical properties and the mesomorphism are strongly affected by the molecular architecture29,31. Thus, an appropriate molecular design is essential to generate new supramolecular liquid crystals with tailored properties. The basic motif of these soft materials lies in a fairly rigid, rod-like moiety linked to one or two flexible aliphatic chains32,33,34. The conventional design of mesomorphic compounds was mainly performed with neutral species but studies have shown that also ionic pairs can exhibit a mesomorphic behavior, yielding materials with properties at the interface between ionic liquids and liquid crystals35,36,37.
Taking into account recent results on XB liquid crystals24,38,39, and the specific ability of anions to act as XB-acceptors, it seemed particularly interesting to exploit this non-covalent interaction in designing new types of ILCs.
1-Alkyl-3-methylimidazolium iodides (1-m) of various chain-length, which are known as ionic liquids40, were used for the synthesis of the complexes (Figure 3)41,42. Note that only 1-12, bearing a C12 alkyl chain, exhibits liquid crystallinity with smectic A (Sm A) phase (crystal (Cr) to SmA transition temperature = 27 &#176;C; Sm A to isotropic liquid (ISO) transition temperature = 80 &#176;C; Cr &#8226; 27 &#8226; SmA &#8226; 80 &#8226; Iso)43. Imidazolium salts were reacted with iodoperfluorooctane (2-8) and iodoperfluorodecane (2-10), which are well-known XB-donors44,45.
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/55636/55636fig3.jpg" /> 
Figure 3: Synthetic scheme. Chemical formulae of starting ionic liquids (1-m), iodoperfluoroalkanes (2-n), and related XB-complexes 1-m&#8226;2-n. <a href="//cloudflare.jove.com/files/ftp_upload/55636/55636fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The iodide anions are expected to participate readily as XB-acceptor in the formation of supramolecular structures with haloperfluoroalkanes44. However, it remains challenging to anticipate the number and topology of the coordinated XB-donor species. In fact, halide anions typically are involved in two or three XBs46,47,48, but higher coordination numbers were also observed49,50.
Herein, we describe a procedure for obtaining highly fluorinated XB ILCs and a detailed procedure for the identification and characterization of the occurrence of XB. The sequence of analysis reported here and utilized to identify the XB can be considered as a general procedure and can be applied to the characterization of any type of XB system.

<table><tbody><tr><td>1-Methyl-imidazole&amp;nbsp;</td><td>Sigma-Aldrich</td><td>M50834-500G</td><td>liquid reagent</td></tr><tr><td>1-Iodoethane</td><td>Sigma-Aldrich</td><td>I7780-100G</td><td>liquid reagent</td></tr><tr><td>1-Iodobutane</td><td>Sigma-Aldrich</td><td>167304-100G</td><td>liquid reagent</td></tr><tr><td>1-Iodohexane</td><td>Sigma-Aldrich</td><td>238287-100G</td><td>liquid reagent</td></tr><tr><td>1-Iodooctane</td><td>Sigma-Aldrich</td><td>238295-25G</td><td>liquid reagent</td></tr><tr><td>1-Iododecane</td><td>Sigma-Aldrich</td><td>238252-100G</td><td>liquid reagent</td></tr><tr><td>1-Iodododecane</td><td>Sigma-Aldrich</td><td>238260-100G</td><td>liquid reagent</td></tr><tr><td>Acetonitrile</td><td>Sigma-Aldrich</td><td>271004-1L</td><td>organic solvent</td></tr><tr><td>Perfluorooctyl iodide&amp;nbsp;</td><td>Apollo Scientific</td><td>PC6170</td><td>fluorinated reagent/halogen-bond donor&amp;nbsp;</td></tr><tr><td>Perfluorodecyl iodide</td><td>Apollo Scientific</td><td>PC5970</td><td>fluorinated reagent/halogen-bond donor&amp;nbsp;</td></tr><tr><td>Bis(2,2,2-trifluoroethyl) ether&amp;nbsp;</td><td>Sigma-Aldrich</td><td>287571-5G</td><td>Internal standard for NMR</td></tr><tr><td>Chloroform-d</td><td>Sigma-Aldrich</td><td>151823-100G</td><td>Solvent for NMR</td></tr></tbody></table>

from molecules to materials: engineering new ionic liquid crystals through halogen bonding

Herein, we demonstrate that a bottom-up approach, based on halogen bonding (XB), can be successfully applied for the design of a new type of ionic liquid crystals (ILCs). Taking advantages of the high specificity of XB for haloperfluorocarbons and the ability of anions to act as XB-acceptors, we obtained supramolecular complexes based on 1-alkyl-3-methylimidazolium iodides and iodoperfluorocarbons, overcoming the well-known immiscibility between hydrocarbons (HCs) and perfluorocarbons (PFCs). The high directionality of the XB combined with the fluorophobic effect, allowed us to obtain enantiotropic liquid crystals where a rigid, non-aromatic, XB supramolecular anion acts as mesogenic core.
X-ray structure analysis of the complex between 1-ethyl-3-methylimidazolium iodide and iodoperfluorooctane showed the presence of a layered structure, which is a manifestation of the well-known tendency to segregation of perfluoroalkyl chains. This is consistent with the observation of smectic mesophases. Moreover, all the reported complexes melt below 100 &#176;C, and most are mesomorphic even at room temperature, despite that the starting materials were non-mesomorphic in nature.
The supramolecular strategy reported here provides new design principles for mesogen design allowing a totally new class of functional materials.

Differential scanning calorimetry (DSC), POM, and thermogravimetric analysis (TGA), as well as 1H and 19F NMR were used to characterize the obtained complexes. Good-quality single crystals of 1-2&#8226;2-8 were obtained from a 1:2 solution of the starting components in acetonitrile by slow evaporation of the solvent at room temperature.
DSC analyses on mixtures of 1-2 and 2-8 with different stoichiometric ratios, allowed us to derive that the right coordination stoichiometry between the imidazolium salt and the iodoperfluoroalkane is 1:2. In fact, the DSC thermogram of the 1:1 complex in Figure 4A shows the presence of the uncomplexed imidazolium salt 1-2 (peak at 57 &#176;C), while in the 1:3 complex there is an excess pure 2-8 (melting point 24 &#176;C). On the other hand, the thermogram of the 1:2 complex shows a single peak distinct from those of the starting compounds, demonstrating that a new pure crystalline species was formed.
TGA analyses confirmed this result. In fact, only upon mixing 1-12 and 2-10 in 1:2 ratio, a homogenous sample was obtained, which released quantitatively the fluorinated building block at a temperature higher than the uncomplexed iodoperfluorodecane (Figure 5A and 5B).
19F NMR has been applied as a simple, effective, and sensitive tool to detect the formation of XB adducts. The XB between the electron deficient iodine of the iodoperfluoroalkanes and the I- anion strongly influences the signals of the -CF2-I group (&#948; = &#8722;60,0 ppm) and gives rise to detectable upfield shifts of the 19F NMR resonances. A &#916;&#948; value of 1.2 ppm was measured for complex 1-2&#8226;2-8, confirming the occurrence of attractive noncovalent interactions involving halogen atoms as electrophilic species (Figure 6). Moreover, by recording consecutive 1H and 19F NMR analyses in the presence of 2,2,2-trifluoroethyl ether as the internal standard for signal integration, the 1:2 stoichiometry between the XB-acceptor and donor modules has been further confirmed.
Single crystal X-ray analysis of 1-2&#8226;2-8 confirmed that the XB drives the formation of a trimeric supramolecular complex where the iodide anion acts as a bidentate XB-acceptor, binding two fluorinated chains. The I&#183;&#183;&#183;I- distances are almost the same [3.4582(9) &#197; and 3.4625(10) &#197;] and roughly correspond to 27% shortening with respect to the sum of the vdW and Pauling radii of the iodine atom and iodide anion, respectively51. The high directionality of XB is confirmed by the C-I&#183;&#183;&#183;I- angles of 174.1(1)&#176; and 175.4(2)&#176;, respectively (Figure 7A). Two equally-populated conformations are observed for the imidazolium cations, which lie approximately on the same plane and are related by a non-crystallographic twofold axis. Figure 7B shows the separation between the ionic and neutral parts, as well as between the HC and PFC chains, within the crystal (disorder removed).
DSC and POM studies revealed that all complexes melted at temperatures lower than 100 &#176;C (Figure 8A), as typical for ionic liquids. Furthermore, they all show an enantiotropic liquid crystalline behavior, some at room temperature, with SmB and SmA phases (Figure 8A). On cooling, the SmA-SmB transition was identified by the characteristic striations across the back of the fans (Figure 8B,left). The striations disappeared on cooling further below the transition.
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/55636/55636fig4.jpg" /> 
Figure 4: Differential Scanning Calorimetry. DSC thermograms of samples prepared by mixing 1-2 and 2-8 in different stoichiometric ratios: 1:3 sample (top), 1:2 sample (mid), and 1:1 sample (bottom). <a href="https://cloudflare.jove.com/files/ftp_upload/55636/55636fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/55636/55636fig5.jpg" /> 
Figure 5:Thermal Analysis. DSC heating/cooling cycles (A) and TGA analysis (B) on a sample prepared by mixing 1-12 and 2-10 in a 1:2 molar ratio. This figure has been modified from reference37. <a href="https://cloudflare.jove.com/files/ftp_upload/55636/55636fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/55636/55636fig6.jpg" /> 
Figure 6:19F NMR Analysis. 19F NMR spectra in CDCl3 of 2-8 (top) and related halogen-bonded complex 1-2&#8226;2-8 (bottom). <a href="https://cloudflare.jove.com/files/ftp_upload/55636/55636fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/55636/55636fig7.jpg" /> 
Figure 7: X-ray single crystal analysis. (A) The asymmetric unit of the complex 1-2&#8226;2-8 showing the formation of a trimeric superanion where two fluorinated chains are bonded to the central I- anion (a single conformer of the disordered cation is reported); (B) The imidazolium salt 1-2 and the iodoperfluorooctane 2-8 segregate along the crystallographic b-axis; (C) Side view showing ionic and fluorocarbon areas of the structure. Color code: grey, carbon; blue, nitrogen; magenta, iodine; green, fluorine; white, hydrogen. Halogen bonds depicted as grey lines. <a href="https://cloudflare.jove.com/files/ftp_upload/55636/55636fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/55636/55636fig8.jpg" /> 
Figure 8: Polarized Optical Microscopy. (A) Chart of thethermal transitions of halogen-bonded complexes 1-m&#8226;2-n measured by hot-stage POM (blue is solid, red is SmB, and orange is SmA phases). (B) Optical textures of the smectic phases observed for 1-12&#8226;2-10 on cooling from the isotropic state. Left: SmB phase at 77 &#176;C; Right: SmA phase at 83 &#176;C.Scale bar: 100 &#181;m. This figure has been modified from reference37. <a href="https://cloudflare.jove.com/files/ftp_upload/55636/55636fig8large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td></td>
			<td>Spectral width (KHz)</td>
			<td>Scans number</td>
			<td>Pulse delay (s)</td>
		</tr>
		<tr>
			<td>1H</td>
			<td>7</td>
			<td>16</td>
			<td>1</td>
		</tr>
		<tr>
			<td>19F</td>
			<td>95</td>
			<td>16</td>
			<td>1</td>
		</tr>
	</tbody>
</table>
Table 1: Acquisition parameters for 1H and 19F NMR experiments

Watch this Scientific Journal Video about From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding at JoVE.com

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding

A protocol for the synthesis of a new type of mesogens, based on the halogen-bonded supramolecular anion [CnF2n+1-I&#183;&#183;&#183;I&#183;&#183;&#183;I-CnF2n+1]&#8722;, is reported.

Herein, we demonstrate that a bottom-up approach, based on halogen bonding (XB), can be successfully applied for the design of a new type of ionic liquid ...

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68.9K Views.  Politecnico di Milano. A protocol for the synthesis of a new type of mesogens, based on the halogen-bonded supramolecular anion [CnF2n+1-I···I···I-CnF2n+1]−, is reported.

Video: From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding

Highly Stereoselective Synthesis of 1,6-Ketoesters Mediated by Ionic Liquids: A Three-component Reaction Enabling Rapid Access to a New Class of Low Molecular Weight Gelators

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form catalytically active N-Heterocyclic Carbenes (NHCs). Here we have used ILs as precatalysts in the addition of &#945;,&#946;-unsaturated aldehydes to chalcones to form 1,6-ketoesters, incorporating an anti-diphenyl moiety in a highly stereoselective fashion. The reaction has a broad substrate scope and several functional groups and heteroaromatics can be integrated into the ketoester backbone in generally good yields with maintained stereoselectivity. The reaction protocol is robust and scalable. The starting materials are inexpensive and the products can be obtained after simple filtration, avoiding solvent-demanding chromatography. Furthermore, the IL can be recycled up to 5 times without any loss of reactivity. Moreover, the 1,6-ketoester end product is a potent gelator in several hydrocarbon based solvents. The method enables rapid access to and evaluation of a new class of low molecular weight gelators (LMWGs) from recyclable and inexpensive starting materials.

Ionic liquids (ILs) mediate fast, simple and cheap access to 1,6-ketoesters in high diastereoselectivities and good yields. The reaction protocol is robust and the 1,6-ketoesters can be obtained in gram scale after a simple filtration protocol. Moreover, the 1,6-ketoesters are potent gelators in hydrocarbon solvents.

In organic chemistry ionic liquids (ILs) have emerged as safe and recyclable reaction solvents. In the presence of a base ILs can be deprotonated to form ...

Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline elastomers (LCEs) with facile control over network structure and programming of an aligned monodomain. Tailored LCE networks were synthesized using routine mixing of commercially available starting materials and pouring monomer solutions into molds to cure. An initial polydomain LCE network is formed via a self-limiting thiol-acrylate Michael-addition reaction. Strain-to-failure and glass transition behavior were investigated as a function of crosslinking monomer, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). An example non-stoichiometric system of 15 mol% PETMP thiol groups and an excess of 15 mol% acrylate groups was used to demonstrate the robust nature of the material. The LCE formed an aligned and transparent monodomain when stretched, with a maximum failure strain over 600%. Stretched LCE samples were able to demonstrate both stress-driven thermal actuation when held under a constant bias stress or the shape-memory effect when stretched and unloaded. A permanently programmed monodomain was achieved via a second-stage photopolymerization reaction of the excess acrylate groups when the sample was in the stretched state. LCE samples were photo-cured and programmed at 100%, 200%, 300%, and 400% strain, with all samples demonstrating over 90% shape fixity when unloaded. The magnitude of total stress-free actuation increased from 35% to 115% with increased programming strain. Overall, the two-stage TAMAP methodology is presented as a powerful tool to prepare main-chain LCE systems and explore structure-property-performance relationships in these fascinating stimuli-sensitive materials.

A novel methodology is presented to synthesize and program main-chain liquid-crystalline elastomers using commercially available starting monomers. A wide range of thermomechanical properties was tailored by adjusting the amount of crosslinker, while the actuation performance was dependent on the amount of applied strain during programming.

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline ...

Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature

The chemical instability of the traditional electrolyte remains a safety issue in widely used energy storage devices such as Li-ion batteries. Li-ion batteries for use in devices operating at elevated temperatures require thermally stable and non-flammable electrolytes. Ionic liquids (ILs), which are non-flammable, non-volatile, thermally stable molten salts, are an ideal replacement for flammable and low boiling point organic solvent electrolytes currently used today. We herein describe the procedures to: 1) synthesize mono- and di-phosphonium ionic liquids paired with chloride or bis(trifluoromethane)sulfonimide (TFSI) anions; 2) measure the thermal properties and stability of these ionic liquids by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA); 3) measure the electrochemical properties of the ionic liquids by cyclic voltammetry (CV); 4) prepare electrolytes containing lithium bis(trifluoromethane)sulfonamide; 5) measure the conductivity of the electrolytes as a function of temperature; 6) assemble a coin cell battery with two of the electrolytes along with a Li metal anode and LiCoO2 cathode; and 7) evaluate battery performance at 100 &#176;C. We additionally describe the challenges in execution as well as the insights gained from performing these experiments.

Here, we describe protocols to prepare phosphonium-based ionic liquid and lithium bis(trifluoromethane)sulfonimide salt electrolytes, and assemble a non-flammable and high temperature functioning lithium-ion coin cell battery.

The chemical instability of the traditional electrolyte remains a safety issue in widely used energy storage devices such as Li-ion batteries. Li-ion ...

Engineering

Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets

In liquid crystal (LC) physical chemistry, molecules near the surface play a great role in controlling bulk orientation. Thus far, mainly to achieve desired molecular orientation states in LC displays, the "static" surface property of LCs, so-called surface anchoring, has been intensively studied. As a rule of thumb, once the initial orientation of LCs is "locked" by specific surface treatments, such as rubbing or treatment with a specific alignment layer, it hardly changes with temperature. Here, we present a system exhibiting an orientational transition upon temperature variation, which conflicts with the consensus. Right on the transition, the bulk LC molecules experience the orientational rotation, with 90&#176; between the planar (P) orientation at high temperatures and the vertical (V) orientation at low temperatures in the first-order transitional manner. We have tracked thermodynamic surface anchoring behavior by means of polarizing optical microscopy (POM), dielectric spectroscopy (DS), high-resolution differential scanning calorimetry (HR-DSC), and grazing incidence X-ray diffraction (GI-XRD) and reached a plausible physical explanation: that the transition is triggered by a growth of surface wetting sheets, which impose the V orientation locally against the P orientation in the bulk. This landscape would provide a general link explaining how the equilibrium bulk orientation is affected by surface-localized orientation in many LC systems. In our characterization, POM and DS are advantageous by offering information on the spatial distribution of the orientation of LC molecules. HR-DSC gives information about the precise thermodynamic information on transitions, which cannot be addressed by conventional DSC instruments due to limited resolution. GI-XRD provides information on surface-specific molecular orientation and short-range orderings. The goal of this paper is to present a protocol for preparing a sample that exhibits the transition and to demonstrate how the thermodynamic structural variation, both in the bulk and on surfaces, can be analyzed through the abovementioned methods.

Here, we present a protocol to trigger an orientational transition of a liquid crystal in response to temperature. Methodologies are described for preparing a sample in order to observe the transition and the detailed transitional evolution.

In liquid crystal (LC) physical chemistry, molecules near the surface play a great role in controlling bulk orientation. Thus far, mainly to achieve ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

We discuss in this article the experimental measurements of the molecules in liquid crystal (LC) phase using the time-resolved infrared (IR) vibrational spectroscopy and time-resolved electron diffraction. Liquid crystal phase is an important state of matter that exists between the solid and liquid phases and it is common in natural systems as well as in organic electronics. Liquid crystals are orientationally ordered but loosely packed, and therefore, the internal conformations and alignments of the molecular components of LCs can be modified by external stimuli. Although advanced time-resolved diffraction techniques have revealed picosecond-scale molecular dynamics of single crystals and polycrystals, direct observations of packing structures and ultrafast dynamics of soft materials have been hampered by blurry diffraction patterns. Here, we report time-resolved IR vibrational spectroscopy and electron diffractometry to acquire ultrafast snapshots of a columnar LC material bearing a photoactive core moiety. Differential-detection analyses of the combination of time-resolved IR vibrational spectroscopy and electron diffraction are powerful tools for characterizing structures and photoinduced dynamics of soft materials.

Here, we present the protocols of differential-detection analyses of time-resolved infrared vibrational spectroscopy and electron diffraction which enable observations of the deformations of local structures around photoexcited molecules in a columnar liquid crystal, giving an atomic perspective on the relationship between the structure and the dynamics of this photoactive material.

We discuss in this article the experimental measurements of the molecules in liquid crystal (LC) phase using the time-resolved infrared (IR) vibrational ...

Microfluidic Preparation of Liquid Crystalline Elastomer Actuators

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation usually consists in the formation of droplets containing low molar mass liquid crystals at elevated temperatures. Subsequently, these particle precursors are oriented in the flow field of the capillary and solidified by a crosslinking polymerization, which produces the final actuating particles. The optimization of the process is necessary to obtain the actuating particles and the proper variation of the process parameters (temperature and flow rate) and allows variations of size and shape (from oblate to strongly prolate morphologies) as well as the magnitude of actuation. In addition, it is possible to vary the type of actuation from elongation to contraction depending on the director profile induced to the droplets during the flow in the capillary, which again depends on the microfluidic process and its parameters. Furthermore, particles of more complex shapes, like core-shell structures or Janus particles, can be prepared by adjusting the setup. By the variation of the chemical structure and the mode of crosslinking (solidification) of the liquid crystalline elastomer, it is also possible to prepare actuating particles triggered by heat or UV-vis irradiation.

This article describes the microfluidic process and parameters to prepare actuating particles from liquid crystalline elastomers. This process allows the preparation of actuating particles and the variation of their size and shape (from oblate to strongly prolate, core-shell, and Janus morphologies) as well as the magnitude of actuation.

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation ...

Preparation of Monodomain Liquid Crystal Elastomers and Liquid Crystal Elastomer Nanocomposites

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and as soft robots. Here, we demonstrate the preparation of shape-responsive liquid crystal elastomers (LCEs) and LCE nanocomposites along with characterization of their shape-responsiveness, mechanical properties, and microstructure. Two types of LCEs &#8212; polysiloxane-based and epoxy-based &#8212; are synthesized, aligned, and characterized. Polysiloxane-based LCEs are prepared through two crosslinking steps, the second under an applied load, resulting in monodomain LCEs. Polysiloxane LCE nanocomposites are prepared through the addition of conductive carbon black nanoparticles, both throughout the bulk of the LCE and to the LCE surface. Epoxy-based LCEs are prepared through a reversible esterification reaction. Epoxy-based LCEs are aligned through the application of a uniaxial load at elevated (160 &#176;C) temperatures. Aligned LCEs and LCE nanocomposites are characterized with respect to reversible strain, mechanical stiffness, and liquid crystal ordering using a combination of imaging, two-dimensional X-ray diffraction measurements, differential scanning calorimetry, and dynamic mechanical analysis. LCEs and LCE nanocomposites can be stimulated with heat and/or electrical potential to controllably generate strains in cell culture media, and we demonstrate the application of LCEs as shape-responsive substrates for cell culture using a custom-made apparatus.

We demonstrate the preparation of siloxane-based and epoxy-based liquid crystal elastomers (LCEs) and LCE nanocomposites. The LCEs are characterized with respect to reversible strain, liquid crystal ordering, and stiffness. As a potential application, we demonstrate their use as shape-responsive substrates in a custom device for active cell culture.

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and ...

Bioengineering

High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal

Smart viscoelastic materials that respond to specific stimuli are one of the most attractive classes of materials important to future technologies, such as on-demand switchable adhesion technologies, actuators, molecular clutches, and nano-/microscopic mass transporters. Recently it was found that through a special solid-liquid transition, rheological properties can exhibit significant changes, thus providing suitable smart viscoelastic materials. However, designing materials with such a property is complex, and forward and backward switching times are usually long. Therefore, it is important to explore new working mechanisms to realize solid-liquid transitions, shorten the switching time, and enhance the contrast of rheological properties during switching. Here, a light-induced crystal-liquid phase transition is observed, which is characterized by means of polarizing light microscopy (POM), photorheometry, photo-differential scanning calorimetry (photo-DSC), and X-ray diffraction (XRD). The light-induced crystal-liquid phase transition presents key features such as (1) fast switching of crystal-liquid phases for both forward and backward reactions and (2) a high contrast ratio of viscoelasticity. In the characterization, POM is advantageous in offering information on the spatial distribution of LC molecule orientations, determining the type of liquid crystalline phases appearing in the material, and studying the orientation of LCs. Photorheometry allows measurement of a material&#8217;s rheological properties under light stimuli and can reveal the photorheological switching properties of materials. Photo-DSC is a technique to investigate thermodynamic information of materials in darkness and under light irradiation. Lastly, XRD allows studying of microscopic structures of materials. The goal of this article is to clearly present how to prepare and measure the discussed properties of a photorheological material.

This protocol demonstrates the preparation of a photorheological material that exhibits a solid phase, various liquid crystalline phases, and an isotropic liquid phase by increasing temperature. Presented here are methods for measuring the structure-viscoelasticity relationship of the material.

Smart viscoelastic materials that respond to specific stimuli are one of the most attractive classes of materials important to future technologies, such ...

Synthesis of Biocompatible Liquid Crystal Elastomer Foams as Cell Scaffolds for 3D Spatial Cell Cultures

Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block co-polymers featuring cholesterol units as side-chain pendant groups, resulting in smectic-A (SmA) liquid crystal elastomers (LCEs). Foam-like scaffolds, prepared using metal templates, feature interconnected microchannels, making them suitable as 3D cell culture scaffolds. The combined properties of the regular structure of the metal foam and of the elastomer result in a 3D cell scaffold that promotes not only higher cell proliferation compared to conventional porous templated films, but also better management of mass transport (i.e., nutrients, gases, waste, etc.). The nature of the metal template allows for the easy manipulation of foam shapes (i.e., rolls or films) and for the preparation of scaffolds of different pore sizes for different cell studies while preserving the interconnected porous nature of the template. The etching process does not affect the chemistry of the elastomers, preserving their biocompatible and biodegradable nature. We show that these smectic LCEs, when grown for extensive time periods, enable the study of clinically relevant and complex tissue constructs while promoting the growth and proliferation of cells.

This study presents a methodology to prepare 3D, biodegradable, foam-like cell scaffolds based on biocompatible side-chain liquid crystal elastomers (LCEs). Confocal microscopy experiments show that foam-like LCEs allow for cell attachment, proliferation, and the spontaneous alignment of C2C12s myoblasts.

Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block ...