Carboxylic Chain Length Research Articles

Exploring pNIPAM lyogels: Experimental study on swelling equilibria in various organic solvents and mixtures, supported by COSMO-RS analysis

Stimuli-responsive lyogels are considered to be smart materials due to their capability of undergoing significant macroscopic changes in response to external triggers. Due to their versatile and unique properties, smart lyogels exhibit great potential in various applications such as drug delivery or actuation processes. While Poly-N-isopropylacrylamide (pNIPAM) is widely known as a thermo-responsive material, it also shows significant solvent-responsive swelling behavior. For the systems tested, polar solvents induce strong swelling due to hydrogen bonding with the amide group, nonpolar solvents lead to significant shrinkage of the lyogels. The aim of this study is to investigate and to model this behavior for future application in chemical or biochemical reactors. As a current area of research, incorporating smart lyogel technology into (bio-)chemical reactors facilitates the development of smart reactor systems. Applying thermodynamic modelling with the gE model COSMO-RS on the monomer or oligomers of pNIPAM, the correlation between solvent-polymer interactions and the degree of swelling can be observed. pNIPAM derivatives exhibit low infinite dilution activity coefficients (IDACs) in polar solvents with large degrees of swelling, while displaying an increase of IDACs in nonpolar solvents. Hydrogen bonds dominate the swelling behavior of lyogels not only in pure solvents but also in mixtures of solvents with varying polarity. Even in mixtures containing high amounts of nonpolar solvents, large degrees of swelling were observed due to the uptake of the polar solvent in the lyogel matrix. This effect can be observed in binary solvent mixtures but also in representative mixtures along an esterification reaction with varying carboxylic chain length of alcohol and carboxylic acids.

Tribological performance of fatty acid ammonium ionic liquids as anti-wear additives in water-based fluids

In this study, we synthesized eight water-soluble ionic liquids (ILs) and investigated their tribological performance as additives in water-diethylene glycol (WDG) base fluids. The results of the tribological test suggested that these ILs additives demonstrate promising capabilities in friction reduction and anti-wear for water lubricated contacts. The ILs with the longest carboxylic chain length, namely C10MIPA and C10DIPA in this work, displayed superior tribological performances. Observations on the abraded surfaces showed that the IL forms a monolayer adsorption through self-assembly, and upon rubbing it creates a continuous and stable tribo-film with an uneven thickness of 30–60 nm through tribo-chemical reactions. The tribo-film mainly consists of iron oxides. The proposed lubrication mechanisms include adsorbed film and formed tribo-films, which work effectively to reduce the shear stress and thus sliding friction.

Lipase-catalyzed synthesis of biobased and biodegradable aliphatic copolyesters from short building blocks. Effect of the monomer length

Biobased short aliphatic diols and diethyl carboxylates were enzymatically (co)polymerized in solution at mild temperature using the immobilized form of Candida antarctica lipase B (CALB) as biocatalyst. The influence of the monomer structure on the CALB activity was investigated. CALB showed a better affinity for 1,4-butanediol compared to 1,3-propanediol (1,3-PDO), whereas no preference was observed between diethyl succinate and diethyl adipate. In addition, two series of random copolyesters [poly(butylene succinate-ran-butylene adipate) (PBSA) and poly(propylene succinate-ran-butylene succinate) (PPBS)] were synthesized at different compositions to investigate the effect of the composition on copolyesters, which were fully characterized by various chemical and physico-chemical techniques including NMR, SEC, WAXS, DSC and TGA. Their compositions were similar to the feed ones, despite the activity difference of the monomers towards CALB. Nevertheless, this activity difference resulted in the decrease of the Mw of PPBS from 24 to 11 kg/mol for 1,3-PDO content varying from 0 to 100 mol.%. Moreover, 1,3-PDO induced an increase of Tg and a decrease of the crystallization rate until having an amorphous behavior for high 1,3-PDO content. On the other side, the reduction of the diethyl carboxylate chain length from diethyl adipate to diethyl succinate did not induce a clear tendency with Mn varying from 22 to 12 kg/mol with the succinate content. Furthermore, Tg increased with the succinate content and the good thermal stability of copolyesters were dependent on the diethyl carboxylates composition. Finally, both copolyesters exhibited an isodimorphic co-crystallization behavior.

Synthesis and Surface Chemistry of Cadmium Carboxylate Passivated CdTe Nanocrystals from Cadmium bis(Phenyltellurolate)

We report the synthesis of cadmium telluride nanocrystals from cadmium bis(phenyltellurolate) (Cd(TePh)2) and cadmium alkylcarboxylates (Cd(O2CR)2, O2CR = oleate, tetradecanoate). Cd(TePh)2 reacts quantitatively with Cd(O2CR)2 at 220 °C over 1 h with the concomitant elimination of diphenyl telluride (Ph2Te) and CdTe nanocrystals. The nanocrystal diameter approaches 3.0–3.2 nm at full conversion regardless of changes to the solvent, carboxylate chain length, heating conditions, and reaction concentration. Larger nanocrystals may be grown by slow addition of additional precursors to the crude product mixture. Isolated nanocrystals have carboxylate ligands (2.1–4.7 nm–2) that can be displaced along with excess cadmium ions using low concentrations of N,N,N′,N′-tetramethylethylenediamine (TMEDA) (1.5–280 mM). Using 1H NMR spectroscopy, we measure the extent of the displacement and show that the binding of Cd(O2CR)2 to CdTe is weaker than to CdSe nanocrystals of similar size. The weaker binding is proposed to ...

Formation of Carboxylic Acid Nanorods on Oleylamide-Capped Au Nanoparticles

This paper describes nanorod formation induced by nanoparticle seeds. Carboxylic acids self-assemble on graphite into an epitaxial pattern. However, this persistent pattern is changed into nanorods by nanoparticles. Two control parameters have been identified, including nucleus/substrate contact angle and seed-to-critical nucleus size ratio. Effective carboxylic chain length and nanoparticle size range are identified, which can be related to the seed size effect. Some nanorods are detached when methyl-terminated nanoparticles are used, and the percentage of detached nanorods increases with increasing carbon chain length. In contrast, the nanorods do not detach from carboxyl-terminated nanoparticles. This study offers direct experimental evidence to molecular simulation prediction that nuclei display a confined morphology on a highly curved seed surface due to the difficulty of maintaining an unstrained structure and they readily detach from the surface during heterogeneous crystal nucleation. This study contributes a solution-based method for the making of nanorods.

Nanoparticles Change the Ordering Pattern of n-Carboxylic Acids into Nanorods on HOPG

This paper describes the formation of organic nanorods induced by monolayer-protected inorganic nanoparticles. Alkanes and alkane derivatives, such as n-carboxylic acids, self-assemble on highly oriented pyrolytic graphite (HOPG) into a persistent molecular packing structure that is dictated by the epitaxial interaction between the carbon chain plane and the HOPG basal plane. Carboxylic acids form 2-D crystalline layers consisting of nanostripe domains whose periodicity is one or two times the molecular chain length. However, when the molecular ordering occurs in the vicinity of a nanoparticle, this persistent HOPG-dominated nanostripe pattern is disrupted, and nanorods attached to the nanoparticles become the dominant structure. In order to understand the underlying mechanism of the nanoparticle-mediated nanorod formation, the effects of film-forming conditions, carboxylic acid chain length, nanoparticle size, and chemical composition of the nanoparticle are examined. It is determined that carboxylic acid nanorods can be induced by nanoparticles of different core materials including CdSe, CdS, and Au, as long as the protecting monolayer allows sufficient dispersion and colloidal stability of the nanoparticles in solution. A carboxylic chain length range amenable to the nanorod formation is identified, as is the relationship between the nanoparticle size and the number of nanorods per nanoparticle. This study contributes to the understanding of seed-mediated crystallization and molecular ordering. Moreover, it defines the parameters governing solution-based formation of hybrid nanostructures and nanopatterns incorporating dual functionality as defined by the inorganic nanoparticle and organic nanorod, respectively.

Effect of cobalt carboxylate precursor chain length on Fischer-Tröpsch cobalt/alumina catalysts

Abstract The effect of the cobalt carboxylate chain length (C2, C5 and C9) on the preparation of alumina supported cobalt catalysts has been studied by TPR, XRD and hydrogen chemisorption techniques. The activity and selectivity of the prepared catalysts have been evaluated for Fischer-Tropsch (FT) activity in a stirred basket reactor. It is shown that for catalysts with Co content of 10 wt.% the activity increases as the carboxylate chain length increases while the selectivity towards methane and light hydrocarbons decreases with the carboxylate chain length. This change relates to the effect of the chain length on the catalyst particle size. The catalyst prepared using cobalt acetate was found to present the highest metal–support interaction and the poorest performance for the Fischer-Tropsch reaction. When the metal content was increased to 15 and 20 wt.% Co, respectively, the metal–support interaction for the catalyst particles prepared from cobalt acetate significantly decreased making it a better catalyst for the FT reaction compared to the catalyst particles prepared from C5 and C9 cobalt carboxylates.

Synthesis of mesoporous zirconium titanates using alkycarboxylate surfactants and their transformation to dense ceramics

Mesoporous zirconium titanates with Ti/Zr ratios of two have been prepared through the controlled hydrolysis of mixtures of zirconium and titanium alkoxides and long chain carboxylates (lauric, palmitic or stearic acids) in the absence of solvent. X-ray diffraction, transmission electron microscopy, and gas adsorption measurements indicate that the zirconium titanate mesophases consist of a disordered arrangement of uniform pores. The average pore diameter obtained depends on the carboxylate chain length. These zirconium titanate mesophases are stable to temperatures in excess of 600 °C and possess a uniform distribution of Zr and Ti within the pore walls without the formation of extraneous phases as determined by XRD and energy dispersive X-ray analysis. The formation of the mesophase was also investigated by small angle X-ray scattering which shows the growth of fractal structures as a function of time. When impregnated with calcium ions the reactive mesoporous precursor can be converted to the dense ceramic, zirconolite, at temperatures as low as 900 °C. The zirconolites formed using the present methods exhibit some compositional variability.

Antibacterial and Antifungal Activity of Zinc(II) CarboxylatesWith/Without N‐Donor Organic Ligands

The antibacterial and antifungal activity of zinc(II) carboxylates with composition Zn(RCOO)2•nH2O(R =H-, CH3-, CH3CH2CH2-, (CH3)2CH-, XCH2-, X=Cl, Br, I, n=0 or 2), [ZnX2(Nia+CH2COO-)2](Nia=nicotinamide, X=Cl, Br, I) and [Zn(XCH2COO)2(Caf)2]•2H2O (Car=caffeine, X=Cl, Br) is studied against bacterial strains Staphylococcus aureus, Escherichia coli and yeast Candida albicans. The structural types are assigned to the prepared compounds and the influence of (i) carboxylate chain length, (ii) substitution of hydrogen atom of carboxylate by halogen and (iii) presence of N-donor organic ligands on the biological activity is discussed.

Intercalation of monoalcohols and dialcohols in vanadyl carboxymethylphosphonate

A series of alcohol-intercalated vanadyl phosphonates VO(HOOCCH 2)PO 3, CH 3(CH 2) nOH (n = 0, 1, 2, 3, 4), and VO(HOOCCH 2)PO 3, OH(CH 2) nOH (n = 3, 4, 5, 6, 8, 10) were prepared in an alcoholic medium. Characterization by X-ray diffraction (XRD), thermogravimetric analysis (TGA), IR spectroscopy, and magnetic measurement is reported. The basal spacing of these lamellar materials increased linearly with the alcohol carboxylic chain length, and pillared material was obtained by dialcohol intercalation. The exchange capacity between alcohol and water is demonstrated and shows that the alcohol OH function is located in the vanadium atom environment, in place of the water molecule that finishes the octahedral coordination of this atom.

A new family of ester lubricants for PVC

AbstractA new class of complex esters offers the capability for tailoring lubrication characteristics to specific PVC applications. The lubricating performance of these esters can be varied from internal to external through changes in carboxylic chain length, polyol moiety, and degree of esterification. Changes in the degree of functionality of the polyol portion of the ester can be used to affect large variations in fusion time and mill stick time. Polyol functionality may also be used to control extrudate gloss without changes in other processing parameters. Dynamic stability is relatively independent of polyol type, with all of the esters providing excellent stability behavior. Carboxylic acid chain length has a pronounced effect on external lubricity, as demonstrated by large changes in mill stick time. Esters based on stearic or longer chain acids provide optimum extrusion processability and yield high gloss extrudates at low extrusion torques. Dynamic thermal stability also increases with acid chain length. The effect of degree of esterifications on lubrication is dependent upon the polyol portion of the ester. In low hydroxyl value esters, the degree of esterification can be used to vary external lubricity.