Alkyl Chain Substituents Research Articles

이핵 CGC의 구조적인 특성과 에틸렌/1-헥센의 공중합 거동과의 관계

Para-xylene의 기본 구조로 연결된 4개의 이핵 CGC를 활용하여 에틸렌과 1-헥센의 공중합특성을 조사하여 중합촉매의 구조적인 특징이 중합에 미치는 영향을 조사하였다. 4가지의 이핵 constrained geometry catalyst(CGC) 중에서 3가지는 모두 para-xylene 다리로 연결되어 있으나 벤젠고리 부분에 각각 다른 치환체가 결합된 것으로서 치 환체는 수소(Catalyst 1), isopropyl(Catalyst 2), n-hexyl(Cataylst 3)이고, n-octyl(Catalyst 4)인 화합물이었 다. 이핵 메탈로센 4가지와 Dow 촉매를 사용하여 에틸렌과 1-헥센을 공중합시켜 다른 치환체를 가진 다리리간드의 구 조적인 특성변화가 촉매의 중합특성과 이로부터 생성되는 공중합체의 특성에 미치는 영향을 조사하였다. 실험 결과 다 리리간드의 특성에 따라 분명한 경향성과 차이점이 발견되었다. 중합활성은 치환체의 크기가 가장 작은 수소에서 가장 높았으며, isopropyl에서 가장 낮았으며 그 차이는 최대 3배 이상이었다. 반면 분자량은 치환체가 isopropyl인 촉매에서 생성된 공중합체가 가장 컸고, n-hexyl과 1-octyl 치환체 화합물에서 가장 작은 분자량의 공중합체가 생성되었으며 그 차이는 6배에 달하였다. 이핵 CGC의 공중합 특성은 치환체가 긴 알킬기인 n-hexyl 및 1-octyl 화합물이 가장 우수하여 동일한 조건에서 1-헥센을 가장 많이 함유하여 40% 이상의 1-헥센을 포함하는 에틸렌 공중합체를 제조할 수 있었다. 이러한 연구 결과는 촉매구조 변화에 의한 고분자 미세구조 조절이라는 고분자 합성의 가장 어려운 부분 이 xylene 다리를 가진 이핵 CGC의 치환체를 조절함으로써 가능함을 보여주는 결과이다.

Synthesis, characterization and in vitro hydrolysis studies of ester and amide prodrugs of dexibuprofen

Ten prodrugs of dexibuprofen having ester and amide moieties instead of free carboxylic acid which involves in gastrointestinal side effects have been synthesized. Dexibuprofen acid chloride was condensed with different amino acid methyl ester hydrochlorides and five alcohols to afford the amide and ester prodrugs. All of the synthesized prodrugs were characterized by their mp, R f, elemental analysis, FTIR, 1H NMR, and 13C NMR spectroscopy. The in vitro hydrolysis studies in plasma reflect prodrugs have been varied in terms of reactivity toward hydrolysis, owing to the different chemical structures. In alkyl substitution the branched chain alkyl substituents or aromatic substituents resulted in enhanced lipophilicity but diminished dissolution and hydrolysis rate. The amide prodrugs with branched and aromatic substitution can also be considered for sustained release. Prodrugs are less irritating to gastric mucosa than dexibuprofen.

Characterization, liquid crystallinity and spin-coated films of some metalated 1,4,8,11,15,18,22,25-octaalkyl tetrabenzo [b,g,l,q][5,10,15]triazaporphyrin derivatives

The preparation and characterization of a number of metalated derivatives of 1,4,8,11,15,18,22,25-octahexyl and 1,4,8,11,15,18,22,25-octadecyl tetrabenzotriazaporphyrins (TBTAPs) are reported. The mesophase behavior of the compounds has been characterized by differential scanning calorimetry (DSC) and by polarized light optical microscopy. Mesophase behavior is compared with data for the corresponding phthalocyanine derivatives reported earlier. The temperature range of the mesophase(s) exhibited by the title compounds is generally broader than those of their phthalocyanine analogs. UV-vis data for examples of the TBTAP compounds as spin-coated films reveal differences in the type of molecular packing in the as-deposited films that is largely dependent upon the length of the alkyl chain substituents. On heating, the films undergo molecular reorganizations at temperatures corresponding to the mesophase transitions of bulk material observed by DSC.

Exploring QSAR, Pharmacophore Mapping and Docking Studies and Virtual Library Generation for Cycloguanil Derivatives as PfDHFR-TS Inhibitors

Resistance of available antimalarial drugs against Plasmodium species is one of the major problems of malaria control in the developing world. In the present study, we have performed QSAR, pharmacophore mapping and molecular docking studies of cycloguanil derivatives as Plasmodium falciparum dihydrofolate reductase thymidylate synthase (PfDHFR-TS) inhibitors to explore essential features required for the antimalarial activity and important interaction patterns between the enzyme and ligands for the design of new potent PfDHFR-TS inhibitors. The QSAR studies have been carried out using topological parameters along with thermodynamic and structural descriptors. Acceptable values of internal and external validation parameters for the developed QSAR models confirm acceptability of the models. Pharmacophore mapping revealed that two hydrogen bond donor (HBD) features and a hydrophobic feature (HYD) are important parameters for PfDHFR-TS inhibitory activity. The docking studies suggest that the PfDHFR-TS inhibitors interact with Asp54, Ile14, Ile164, ser108, Ser111, Tyr170, Met55, Ala16, Thr185, Leu46, Cys15, Phe58, Ile112, Trp48, Tyr57 and Leu119 amino acid residues. The QSAR, pharmacophore and docking studies inferred that i) branching of the substituents at R1 and R2 positions should be less (small alkyl chain substituents are favored); ii) the electronegativity of the molecules should be high but within some limit; iii) the size and volume of the molecules should be high; iv) molecules should be flexible enough; v) R configuration at C6 position of the triazine ring favors the inhibitory binding affinity; vi) the substituents of the phenyl ring at 3, 4 and 5 position of the phenyl ring should be small hydrophobic groups. Based on these studies, we have designed a library of cycloguanil derivatives with good in silico predicted PfDHFR-TS inhibitory activity.

Deterpenation of Citrus Essential Oil by Liquid−Liquid Extraction with 1-Alkyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)amide Ionic Liquids

Three 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquids, namely, those with ethyl-, hexyl-, or decyl- as the alkyl substituent chain, were evaluated as potential solvents for the deterpenation of citrus essential oil by liquid−liquid extraction. The citrus essential oil was simulated as a mixture of the terpene limonene and the oxyterpene linalool. The liquid−liquid equilibrium data for the ternary systems formed by limonene, linalool, and each of the ionic liquids selected were experimentally determined at 298.15 K. The suitability of the ionic liquids as solvents for the proposed process was evaluated by means of solute distribution ratio and selectivity values. The influence of the alkyl side chain in the imidazolium cation of the ionic liquids on the liquid−liquid equilibrium data was analyzed. By comparison with data previously reported in the literature for analogous systems, the influence of the ionic liquid anion on the proposed separation was also analyzed. The experimen...

Ultrahigh Mobility in Polymer Field-Effect Transistors by Design

In this article, the design paradigm involving molecular weight, alkyl substituents, and donor-acceptor interaction for the poly[2,6-(4,4-bis-alkyl-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (cyclopentadithiophene-benzothiadiazole) donor-acceptor copolymer (CDT-BTZ) toward field-effect transistors (FETs) with ultrahigh mobilities is presented and discussed. It is shown that the molecular weight plays a key role in improving hole mobilities, reaching an exceptionally high value of up to 3.3 cm(2) V(-1) s(-1). Possible explanations for this observation is highlighted in conjunction with thin film morphology and crystallinity. Hereby, it is found that the former does not change, whereas, at the same time, crystallinity improved with ever growing molecular weight. Furthermore, other important structural design factors such as alkyl chain substituents and donor-acceptor interaction between the polymer backbones potentially govern intermolecular stacking distances crucial for charge transport and hence for device performance. In this aspect, for the first time we attempt to shed light onto donor-acceptor interactions between neighboring polymer chains with the help of solid state nuclear magnetic resonance (NMR). On the basis of our results, polymer design principles are inferred that might be of relevance for prospective semiconductors exhibiting hole mobilities even exceeding 3 cm(2) V(-1) s(-1).

Novel Alkoxyaryl Substituted Porphyrins with Terminal Carboxymethyl and Carboxy Groups: Synthesis and Mesomorphic Properties

Design of nanostructured materials based on amphiphilic porphyrins and their metal complexes is a new promising area.[1,2] Porphyrins have all the necessary properties, including the availability of precursors, simplicity of synthesis and functionalization, thermal stability and specific photochemical properties, and the amphiphilic structure is crucial for self-assembly of supramolecular assemblies through noncovalent interactions.[1–3] In this respect, liquid crystalline (LC) state is regarded as a way of achieving structural self-organization.[1] Usually, to obtain the LC properties of tetrapyrrolic compounds the macrocycle is functionalized by long chain alkyl substituents, what also improves the solubility in nonpolar solvents and promotes surface immobilization.[4] The introduction of metal usually leads to a change in mesomorphic properties.[4,5] It is proved that the LC-based porphyrins are promising for optoelectronics, device display and storage.[6–8] By now, a large number of mesogenic lipophilic porphyrins (both ligands and their metal complexes) with thermotropic and lyotropic mesomorphism have been described.[4–8] It has also been reported that amphiphilic porphyrin derivatives containing sulfogroups possess lyotropic mesomorphism.[9,10] We have demonstrated for cationic derivatives of 5,10,15,20-tetra-meso-aryl substituted porphyrins with terminal pyridinium groups that amphiphilic porphyrins possess thermotropic mesomorphism. At the same time a significant effect of the length of the aliphatic spacer and the metal nature on the liquid crystalline properties has been discovered.[11] In this work we have synthesized the structural analogs of the above mentioned cationic porphyrins – amphiphilic tetraalkoxyaryl porphyrins (1–5) and studied their mesomorphic properties. These compounds have long chain substituents in which the spacer methylene chains with a length of five or ten carbon atoms separate the carboxy or carboxymethyl groups from the porphyrin macrocycle. To obtain the 5,10,15,20-tetrasubstituted porphyrins 1 – 3 we used an improved method of monopyrrole condensation in which the maximum yields of porphyrins were achieved at the concentrations of benzaldehyde and pyrrole equal to 10-2 M.[12] Based on the relevant substituted 4-hydroxybenzaldehyde and pyrrole according to the developed approach to the synthesis of lipophilic porphyrins[13] we synthesized symmetrical meso-tetrakis(4-(methoxycarbonylalkyloxyphe

Proactive Aquatic Ecotoxicological Assessment of Room-Temperature Ionic Liquids

Aquatic environments are being contaminated with a myriad of anthropogenic chemicals, a problem likely to continue due to both unintentional and intentional releases. To protect valuable natural resources, novel chemicals should be shown to be environmentally safe prior to use and potential release into the environment. Such proactive assessment is currently being applied to room-temperature ionic liquids (ILs). Because most ILs are water-soluble, their effects are likely to manifest in aquatic ecosystems. Information on the impacts of ILs on numerous aquatic organisms, focused primarily on acute LC50 and EC50 endpoints, is now available, and trends in toxicity are emerging. Cation structure tends to influence IL toxicity more so than anion structure, and within a cation class, the length of alkyl chain substituents is positively correlated with toxicity. While the effects of ILs on several aquatic organisms have been studied, the challenge for aquatic toxicology is now to predict the effects of ILs in complex natural environments that often include diverse mixtures of organisms, abiotic conditions, and additional stressors. To make robust predictions about ILs will require coupling of ecologically realistic laboratory and field experiments with standard toxicity bioassays and models. Such assessments would likely discourage the development of especially toxic ILs while shifting focus to those that are more environmentally benign. Understanding the broader ecological effects of emerging chemicals, incorporating that information into predictive models, and conveying the conclusions to those who develop, regulate, and use those chemicals, should help avoid future environmental degradation. Keywords: Aquatic toxicology, ecotoxicology, bioassay, mesocosm, interdisciplinary collaboration, Aquatic environments, abiotic conditions, oxygen depletion, thermal extremes, anthropogenic, flow alterations, non-native species, quantitative structure-property relationships (QSPR), physiologically-based pharmacokinetic (PBPK) models, biotic interactions, polychlorinated biphenyl (PCB), ecological risk

Ionic liquids and organic ionic plastic crystals utilizing small phosphonium cations

The development of new liquid and solid state electrolytes is paramount for the advancement of electrochemical devices such as lithium batteries and solar cells. Ionic liquids have shown great promise in both these applications. Here we demonstrate the use of phosphonium cations with small alkyl chain substituents, in combination with a range of different anions, to produce a variety of new halide free ionic liquids that are fluid, conductive and with sufficient thermal stability for a range of electrochemical applications. Walden plot analysis of the new phosphonium ionic liquids shows that these can be classed as “good” ionic liquids, with low degrees of ion pairing and/or aggregation, and the lithium deposition and stripping from one of these ionic liquids has been demonstrated. Furthermore, for the first time phosphonium cations have been used to form a range of organic ionic plastic crystals. These materials can show significant ionic conductivity in the solid state and thus are of great interest as potential solid-state electrolyte materials.

Amphiphilic Ruthenium(II) Terpyridine Sensitizers with Long Alkyl Chain Substituted β-Diketonato Ligands: An Efficient Coadsorbent-Free Dye-Sensitized Solar Cells

Three alkyl-substitutedβ-diketonato-ruthenium(II)-polypyridyl sensitizers with different alkyl chain lengths, [Ru(tctpy)(tfpd)(NCS)] (A1), [Ru(tctpy)(tfdd)(NCS)] (A2), and [Ru(tctpy)(tfid)(NCS)] (A3), were designed and synthesized for dye-sensitized solar cells (DSCs) to investigate the effect of bulky alkyl chain substituents on the photovoltaic performances (where tctpy = 4,4′,4′′-tricarboxy-2,2′:;6′,2′′-terpyridine, tfpd =1,1,1-trifluoropentane-2,4-dione, tfdd = 1,1,1-trifluorodecane-2,4-dione, and tfid =1,1,1-trifluoroicosane-2,4-dione). These complexes exhibit a broad metal-to-ligand charge transfer absorption band over the whole visible range extending up to 950 nm. All complexes were examined in the presence and absence of the coadsorbent deoxycholic acid (DCA) in dye-bath solutions. These sensitizers, when anchored to nanocrystalline TiO2films, achieve efficient sensitization to TiO2electrodes. Under standard AM 1.5 sunlight, the complexA3containing long alkyl chain length of C16yielded a short-circuit photocurrent density of 18.0 mA/cm2, an open-circuit voltage of 0.64 V, and a fill factor of 0.66, corresponding to an overall conversion efficiency of 7.6% in the absence of DCA. The power conversion efficiency ofA1sensitized DSCs was significantly increased upon the addition of DCA as compared to that in the absence of DCA. However, the photovoltaic performance ofA3was not dependent on DCA at all, probably due to the inherent structural nature of theA3molecule.

Cytotoxicity of 1-alkylquinolinium bromide ionic liquids in murine fibroblast NIH 3T3 cells

Minimal toxicity data are available for 1-alkylquinolinium bromide ionic liquids. Here, their toxicity to NIH 3T3 murine fibroblast cells, of relevance to their potential antimicrobial application, is presented. Toxicity data, presented by time-point analysis with a particular focus on the immediate toxicity upon short term cellular exposure, indicate a link between the length of the alkyl chain cationic substituent and resultant biological toxicity. 1-Tetradecylquinolinium bromide was found to exhibit cellular toxicity comparable to benzalkonium chloride over all time points tested. By comparison, 1-octylquinolinium bromide initially exerted significantly lower cytotoxicity at one hour; however, toxicity was found to have a cumulative effect over time-course analysis up to three days. This illustrates that cationic substituent alkyl chain length may govern not only overall toxicity, but also the rate of toxicity. Fluorescence microscopy was utilised to examine destabilisation of the plasma membrane by 1-tetradecylquinolinium bromide and benzalkonium chloride after one hour, with membrane destabilisation not observed for 1-octylquinolinium bromide, or the base constituent quinoline.

Small angle neutron scattering from 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids ([Cnmim][PF6], n=4, 6, and 8)

The presence of local anisotropy in the bulk, isotropic, and ionic liquid phases-leading to local mesoscopic inhomogeneity-with nanoscale segregation and expanding nonpolar domains on increasing the length of the cation alkyl-substituents has been proposed on the basis of molecular dynamics (MD) simulations. However, there has been little conclusive experimental evidence for the existence of intermediate mesoscopic structure between the first/second shell correlations shown by neutron scattering on short chain length based materials and the mesophase structure of the long chain length ionic liquid crystals. Herein, small angle neutron scattering measurements have been performed on selectively H/D-isotopically substituted 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids with butyl, hexyl, and octyl substituents. The data show the unambiguous existence of a diffraction peak in the low-Q region for all three liquids which moves to longer distances (lower Q), sharpens, and increases in intensity with increasing length of the alkyl substituent. It is notable, however, that this peak occurs at lower values of Q (longer length scale) than predicted in any of the previously published MD simulations of ionic liquids, and that the magnitude of the scattering from this peak is comparable with that from the remainder of the amorphous ionic liquid. This strongly suggests that the peak arises from the second coordination shells of the ions along the vector of alkyl-chain substituents as a consequence of increasing the anisotropy of the cation, and that there is little or no long-range correlated nanostructure in these ionic liquids.

Room temperature anthracene excimer emission from self-assembled (aminomethyl)anthracene derivatives in plastic crystalline phase

A series of (aminomethyl)anthracene ( AMA) derivatives with single alkyl chain substituent (octyl, dodecyl, octadecyl and p-butylaniline) were synthesized and self-assembly of the compounds was analyzed in dichloromethane and solid thin film. Upon heat treatment of the solid thin films, the AMA derivatives exhibit plastic crystalline phase which can be preserved in a glassy state through rapid cooling of the system to room temperature. In the glassy state, the AMA derivatives are arranged in rectangular discotic columnar fashion, where the face-to-face distance between two anthracene moieties is 3.9 Å. Steady state and time resolved fluorescence studies were carried out in dichloromethane, which indicate that a fraction of the AMA derivatives form anthracene excimer, upon excitation at 360 nm. Conversely, photoexcitation of the solid thin film at 360 nm leads to the exclusive formation of anthracene excimers due to the close proximity of anthracene units in the discotic columnar arrangement. Furthermore, the self-assembled AMA derivatives were utilized as effective templates for in situ prepared Ag nanoparticles. While the AMA derivatives stabilize the Ag nanoparticles effectively, the excimer emission intensity was quenched in the presence of silver nanoparticles. The experimental results from the present study provide a unique approach for generating anthracene excimer emission from solid thin films at room temperature, which is a rare observation.

ChemInform Abstract: Liquid Crystal Properties of Metal-Salicylaldimine Complexes. Chemical Modifications Towards Lower Symmetry

Abstract A body of work involving liquid crystalline phases in the family of transition metal complexes of salicylaldimines has been reviewed. An account is given as to how the mesophases can be derived from archetypical coordination compounds in the liquid state by an approach of lowering symmetry. Attention is confined to reported examples of well-established metal–salicylaldimine mesogens. Firstly, it is shown that the nematic behavior can be related to the molecular shape anisotropy as a primary factor, which works advantageously to generate the orientational order. A group of bis[4-(4-alkoxy)benzoyloxy-N-alkylsalicylaldiminato]metal complexes represents the nematics. Smectic fluctuations in, and eventual ordering of, the nematic phases are treated together, and several other effects conducive to this tailoring of phase property are pointed out. Pure smectic phases are found in bis[4-alkoxy-N-arylsalicylaldiminato]metal complexes. The change in the rigid core shape and the packing considerations for the terminal alkyl chain substituents are discussed in relation to the positional ordering. The literature is cited to shed light on the increased biaxial character of the molecular structure possibly leading to unusual local ordering. Finally, columnar phases in complexes of [M(salen)] type with heavily incorporated long alkyl chains are introduced and contrasted to simpler dialkylated derivatives which are smectogenic.

Room-temperature spin crossover and Langmuir–Blodgett film formation of an iron(ii) triazole complex featuring a long alkyl chain substituent: the tail that wags the dog

[Fe(II)(C(16)dpt)(2)(NCS)(2)].(2/3)H(2)O displays temperature-mediated spin crossover (SCO) with T((1/2)) = 290 K and the long alkyl chain substituent on the dipyridyltriazole ligand facilitates the formation of a stable Langmuir-Blodgett film at an air-water interface.

Controlled growth of BaMoO4 hierarchical superstructures in functionalized ionic liquids

Abstract Dual-functionalized ionic liquids (ILs) containing both functionalized cation and anion offer scope for tuning of nucleation and growth steps to achieve crystallographic control. BaMoO4 crystals synthesized in alkyl methylimidazolium trifluoroacetate ([C n mim]TA, n = 4, 8, 16) aqueous solution display the similar shuttle-like shape. The size of building blocks assembling into the hierarchical architectures has been influenced by the inhibiting effect of the imidazolium substituent alkyl chain. With the increase of imidazolium substituent alkyl chain length, the building blocks change from the truncated octahedron to the nanosheet. The single-crystalline BaMoO4 dendrites were prepared under the direction of [Omim]TA via the oriented attachment mechanism. BaMoO4 porous structures have been successfully synthesized in the [Omim]TA aqueous solution via the manipulation of the growth kinetics. Whether the resultant holes in the BaMoO4 structure are open or clogged depends upon variations in the molar ratio [Ba2+]/[Mo7O24 6–]. Shuttle-like BaMoO4 crystals made of nanosheets with the helical growth features have been successfully synthesized in the presence of [C16mim]TA. In addition, the amount of [C16mim]TA in the solution profoundly influences the morphology and size of the as-obtained products.

Electrochemical preparation of an electroactive polymer poly(dodecyloxy dibenzothiophene) (polyDDBTh) from hydroxyl dibenzothiophene (HDBTh) as a bioconverted monomer

A combination of biotechnological and electrochemical techniques is employed to synthesize an electroactive π-conjugated polymer. The monomer precursor bearing a hydroxyl group is obtained by the bioconversion of dibenzothiophene. An alkyl chain substituent is introduced by Williamson etherification with the aid of crown ether, and electrochemical polymerization is carried out by repeated potential scanning of the monomer in an electrolytic reaction solution. The polymer film thus prepared is shown to exhibit good electroactive characteristics.

Biphasic liquid mixtures of ionic liquids and polyethylene glycols

We have found that 1-alkyl-3-methylimidazolium chloride ionic liquids (ILs) can form immiscible liquid mixtures with some polyethylene glycols (PEGs). Binary mixtures of 1-ethyl-3-methylimidazolium chloride with PEG of molecular weight 1500, 2000, or 3400 g mol(-1), or of 1-butyl-3-methylimidazolium chloride with PEG of molecular weight 2000 or 3400 g mol(-1), have been found to give rise to entirely liquid, stable biphasic systems over a significant temperature range (from 333.15 K to 413.15 K), while mixtures of 1-ethyl-3-methylimidazolium chloride with PEG-1000 and 1-butyl-3-methylimidazolium chloride with PEG-1000 and PEG-1500 are miscible. The mutual immiscibility of the IL and the PEG increases as the temperature increases. The evolution of the composition of the phases in equilibrium with the molecular weight of the PEG, or with the variation of the length of the alkyl substituent chain of the imidazolium cation of the IL, has been explored. The trends observed are explained through the complexity of interactions present within the binary system. A thermodynamic analysis of the liquid-liquid equilibrium data indicates negative values for the change of enthalpy and entropy of mixing. The potential application of these biphasic, entirely liquid systems, with low volatility and good solvation properties, for the dissolution and separation of cellulose and lignin at elevated temperature has been preliminarily explored, although only modest results have been achieved to date.

Synthesis, thermal stabilities, and anisotropic properties of some new isoflavone‐based esters 7‐decanoyloxy‐3‐(4′‐substitutedphenyl)‐4H‐1‐benzopyran‐4‐ones

A series of new isoflavonic esters 7‐decanoyloxy‐3‐(4′‐substitutedphenyl)‐4H‐1‐benzopyran‐4‐ones containing a heterocycle in their central core with one flexible alkyl chain and various substituents, R (where R = F, Cl, Br, CH3, OCH3, or H) at 4′‐position at one end, have successfully been synthesised, isolated, and characterised. The physical properties of title compounds were studied using spectroscopic techniques (Fourier transform infrared, 1H and 13C nuclear magnetic resonance). The liquid crystalline properties and the textures of these compounds along with their thermal stabilities were investigated via polarising optical microscopy and differential scanning calorimetry. All the compounds except the member without the substituent were enantiotropic mesogens exhibiting smectic A and/or nematic phases. The layer periodicities in relation to different phases were substantiated by X‐ray diffraction wherein the molecules within the SmA phase were found to be intercalated. The structural changes that resulted in a variation of transition temperature as well as the electronic polarisability of the respective compounds are also discussed.

Tribological properties of ionic liquids as lubricants and additives. Part 1: Synergistic tribofilm formation between ionic liquids and tricresyl phosphate

The use of imidazolium tetrafluoroborate, IMM+BF4−, and hexafluorophosphate, IMM+PF6−, ionic liquids as lubricants was investigated at 25 and 100 °C to show lower friction coefficients but higher wear rates than a reference hydrocarbon lubricant. The ionic liquids readily form tribofilms at the lower temperature but have difficulty in forming partial films at the higher temperature. Wear tracks for a Plint TE77 reciprocating ball-on-plate test using ionic liquids show smoother surfaces, with small pits developing, compared to the reference hydrocarbon lubricant test result. Similar ionic liquids not containing fluorine were found to be less effective as lubricants. Addition of ionic liquids to a base grease and a formulated high temperature grease gave surprisingly large increases in the weld load for the Four Ball extreme pressure test. Little difference between base grease and base grease+5 per cent ionic liquid was observed for the TE77 test. There was no clear indication of the effect of alkyl substituent chain length on the imidazolium cation for the Four Ball test wear scar diameter. Addition of 1 per cent tricresyl phosphate (TCP) to ionic liquids rapidly establishes a tribofilm and reduces the wear volume by 64 per cent compared to the same test for the neat ionic liquid or neat TCP. Addition of 1 per cent TCP and 1 per cent ionic liquid to a Group III base oil also establishes a substantial tribofilm and reduces wear volumes compared to the base oil with 1 per cent TCP alone or the base oil with 1 per cent ionic liquid alone. Ionic liquids show promise as neat liquid lubricants by establishing a tribolayer chemically adsorbed to the steel surfaces. They are not as effective as a reference hydrocarbon lubricant in reducing wear of those surfaces by tribocorrosion. The fluorine-free ionic liquids investigated were not as effective as those containing fluorine. The addition of ionic liquids to grease, base or fully formulated, gave a substantial improvement in performance, which indicates a synergistic interaction with the additives present in the formulated grease. There is also clear evidence of a strong synergistic effect between ionic liquids and TCP, both for the neat ionic liquids and for 1 per cent dilution of each respectively in a Group III base oil to give a thick tribofilm and substantially reduced wear in the TE77 ball-on-plate test. The nature of the synergy between ionic liquids and TCP requires further investigation.