Pyromellitic-Based Low Molecular Weight Gelators and Computational Studies of Intermolecular Interactions: A Potential Additive for Lubricant.

Low molecular weight gelators (LMWG) have been extensively explored in many research fields due to their unique reversible gel-sol transformation. Intermolecular interactions between LMWG are known as the main driving force for self-assembly. During this self-assembly process, individually analyzing the contribution difference between various intermolecular interactions is crucial to understand the gel properties. Herein, we report 2,5-bis(hexadecylcarbamoyl)terephthalic acid (BHTA) as a LMWG, which could efficiently form a stable organogel with n-hexadecane, diesel, liquid paraffin, and base lubricant oil at a relatively low concentration. To investigate the contribution difference of intermolecular interactions, we first finished FT-IR spectroscopy and XRD experiments. On the basis of the d-spacing, a crude simulation model was built and then subjected to molecular dynamics (MD) simulations. Then, we knocked out the energy contribution of the H-bonding interactions and π-π stacking, respectively, to evaluate the intermolecular interactions significantly influencing the stability of the gel system. MD simulations results suggest that the self-assembly of the aggregates was mainly driven by dense H-bonding interactions between carbonyl acid and amide moieties of BHTA, which is consistent with FT-IR data. Moreover, wave function analysis at a quantum level suggested these electrostatic interactions located in the middle of the BHTA molecule were surrounded by strong dispersion attraction originating from a hydrophobic environment. Furthermore, we also confirmed that 2 wt % BHTA was able to form gel lubricant with 150BS. The coefficient of friction (COF) data show that the gel lubricant has a better tribological performance than 150BS base lubricant oil. Finally, XPS was performed and offered valuable information about the lubrication mechanism during the friction.

Scaleable two-component gelator from phthalic acid derivatives and primary alkyl amines: acid-base interaction in the cooperative assembly.

A series of phthalic acid derivatives (P) with a carbon-chain tail was designed and synthesized as single-component gelators. A combination of the single-component gelator P and a non-gelling additive n-alkylamine A through acid-base interaction brought about a series of novel phase-selective two-component gelators PA. The gelation capabilities of P and PA, and the structural, morphological, thermo-dynamic and rheological properties of the corresponding gels were investigated. A molecular dynamics simulation showed that the H-bonding network in PA formed between the NH of A and the carbonyl oxygen of P altered the assembly process of gelator P. Crude PA could be synthesized through a one-step process without any purification and could selectively gel the oil phase without a typical heating-cooling process. Moreover, such a crude PA and its gelation process could be amplified to the kilogram scale with high efficiency, which offers a practical economically viable solution to marine oil-spill recovery.

Crossed-aldol condensation of cycloalkanones with aromatic aldehydes catalyzed by copper(II) trifluoroacetate.

A simple and solvent-free procedure to synthesize alpha,alpha'-bis(substituted benzylidene) cycloalkanones, catalyzed by copper(II) trifluoroacetate through crossed-aldol condensation of various aromatic aldehydes with cyclic ketones is reported. The reaction proceeded smoothly in good to excellent yields.

A complementarity for extended Langmuir method.

The interaction free energy per unit area between parallel flat plates with high surface potential in the case of constant surface potential is again presented. It is complementarity for extended Langmuir method [G. Luo, H. Wang, J. Jin, Langmuir 17 (2001) 2167 and G. Luo, R. Feng, J. Jin, H. Wang, J. Colloid Interface Sci. 241 (2001) 81]. These approximate expressions work quite well for all values of the surface potentials so as the plates separations are small.

An Efficient one-pot Biginelli condensation of aliphatic aldehydes catalyzed by zinc bromide under solvent-free conditions.

Zinc bromide catalyzes the three component condensation reaction of an aldehyde, urea, and beta-ketoester or beta-diketone under solvent-free conditions to afford the corresponding dihydropyrimidinones (DHPMs) with moderate to high yields in short reaction time. The present method is very effective for the Biginelli condensation of aliphatic aldehydes.

One-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones using chloroacetic acid as catalyst.

A simple and effective synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives from aldehydes, 1,3-dicarbonyl compounds and urea or thiourea using chloroacetic acid as catalyst under solvent-free conditions is described. Compared with the classical Biginelli reaction conditions, this new method has the advantage of good to excellent yields and short reaction time.

A highly efficient solvent-free synthesis of benzoxanthenes catalyzed by methanesulfonic Acid.

A series of 14-alkyl and aryl-14H-dibenzo[a, j]xanthenes have been synthesized through a one-pot condensation of beta-naphthol with alkyl or aryl aldehydes, in the presence of methanesulfonic acid in a solvent-free medium, with high yields.

One-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones using CuBr2 as catalyst.

A simple, efficient procedure and improved conditions have been found to carry out the Biginelli reaction for the synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives. This synthesis was performed using CuBr2 as the catalyst in ethanol solution. The optimum conditions were as follows: the molar ratio of aldehyde to alpha,beta-diketone to urea or thiourea is 1:1:1:0.5, the molar ratio of catalyst to aldehyde is 25%, and the reaction time is 4 h. Under the above conditions, the highest yield of dihydropyrimidinones was up to 95%. Compared with the classical Biginelli reaction conditions, this new method has the advantage of excellent yields and short reaction times.