Introduction Of Acid Groups Research Articles

Acid acceptor modulated interfacial polymerization with piperazine-2-carboxylic acid as diamine monomer for ultrathin polyamide nanofiltration membrane

When introducing acid groups in the diamine monomer for the fabrication of polyamide (PA) membranes through interfacial polymerization (IP), the acid groups not only reduce the diffusion flux of diamine monomer for the polymerization to prepare ultrathin membrane but also provide the negative charges on the membrane surface. However, the introduction of acid groups often weakens the reactivity of diamine monomers, resulting in the formation of thick and loose PA membranes with low rejection of ions. This study proposes a strategy of modulating the IP process of piperazine-2-carboxylic acid (CPIP) by employing an acid acceptor (NaOH) to prepare thin nanofiltration membranes. The acid acceptor can neutralize the HCl to prevent CPIP from being protonated during the IP process, thereby facilitating the cross-linking reaction rate. The thickness of the resulting membrane decreases from 180 nm to 30 nm, accompanied by the fortification of the negative charge, an increase in cross-linking density, and a reduction in pore size. The resulting PA-AA/CPIP_1.0 membrane exhibits a water permeance of 44.6 L m−2 h−1 bar−1, with a significantly increased Na2SO4 rejection of 98.4 % compared with 50.4 % of the PA-AA/CPIP_0 membrane fabricated without acid acceptor. This work may open a new avenue to fabricating high-performance PA membranes for nanofiltration.

Pyridine Ionic Liquid-Based Deep Eutectic Solvents Selectively Separating Toluene from Alkanes

Naphtha is an important raw material for ethylene cracking, and the aromatics in it can affect the ethylene yield due to the easy coking during the cracking process. Therefore, it is important to separate the aromatics from naphtha to increase the alkane content and improve the ethylene cracking production. Liquid–liquid extraction separation of the aromatic/alkane mixture is one of the effective pathways, and the key is the design and synthesis of new efficient extractants. In this work, a novel pyridine ionic liquid-based deep eutectic solvent (DES) for the separation of aromatics from alkanes was proposed and successfully synthesized. 1-Ethylpyridinium chloride (EpyCl) was used as the hydrogen bond acceptor and levulinic acid (LA) as the hydrogen bond donor. Among them, the π–π interactions between pyridine ring, C═O, and aromatic ring can enhance the interactions with aromatic compounds. In contrast, the introduction of acidic groups can increase the polarity of DES, enhance the induced polarization of unsaturated bonds in aromatic rings by DES, and thus increase the non-bonding force with aromatics. Toluene/n-heptane and toluene/cyclohexane were used as simulated oil systems. The optimal ratio of EpyCl/LA is 2:1, which has the best extraction efficiency, stability, and reusability; the selectivity of toluene was up to 69.57 for the toluene-n-heptane system, while it was 24.41 for the toluene-cyclohexane system. The reliability of the liquid–liquid equilibrium data was verified by using the Othmer–Tobias correlation equations, and the basic system physical property data were obtained by fitting with the NRTL thermodynamic model. The interaction mechanism between DES and toluene/alkanes was revealed by AIM topology analysis, IGMH analysis, and symmetry-adapted perturbation theory energy decomposition. The interaction between DES and toluene/alkanes is a van der Waals force, dominated by dispersion forces.

Highly Efficient Electrocarboxylation Method to Synthesize Novel Acid Derivatives of 1,4-Dihydropyridines and to Study Their Antimicrobial Activity.

1,4-Dihydropyridines (1,4-DHPs) hold a top-notch position in the pharmaceutical world due to a broader spectrum of applications, whereas the carboxylic moiety has been an integral part of the physiological world, effective food preservatives, and antimicrobial agents. Seeking the enormous potential and applications of these two classes, we worked to combine these to synthesize 2,2′-[3,5-bis(ethoxycarbonyl)-4-phenyl-1,4-dihydropyridine-2,6-diyl]diacetic acid the novel dicarboxylic derivatives of 1,4-DHP (9a–k) achieved via the electro-carboxylation of tetrasubstituted-1,4-dihydropyridines (8a–k) derivatives using Mg–Pt electrodes in an undivided cell. The targeted compounds were established by 1H, 13C NMR, IR, and ESI-MS. Further, the synthesized compounds show excellent resistance against various microbes and the activity increased 2–3 folds after the introduction of acid groups. Compound 9b (against E. coli, S. aureus, B. subtilis, A. niger, and P. glabrum), 9d (against E. coli, K. pneumonia, S. aureus, A. janus, and F. oxysporum), 9f (against E. coli and P. fluorescens), and 9k (against F. oxysporum and P. glabrum) were found to be highly active at 4 μg/mL with reference to standard amoxicillin and fluconazole. Further, the present synthetic protocol would open new gates for other researchers to develop new molecules by bioisosteres of these substrates.

A novel bio-based benzoxazine resin with outstanding thermal and superhigh-frequency dielectric properties

A novel bio-based benzoxazine was synthesized from diphenolic acid and furfurylamine through the facile one-pot formulation method. In comparison with other bio-based thermosetting resins and bio-based benzoxazine resins, the prepared benzoxazine resin had the advantages of accelerated curing behavior, relatively good thermal properties (Tg, 303 °C; char yield (800 °C), 54%), and relatively low superhigh-frequency dielectric constants (2.97 ± 0.01, 5 GHz; 2.95 ± 0.01, 10 GHz; 2.90 ± 0.01, 15 GHz), resulting from the introduction of acidic groups and furan rings. Therefore, this work not only provides a new strategy for the preparation of biomass-based benzoxazine resin with superhigh-frequency low dielectric constants, but also gives some insight into the effects of pentanoic acid and furan rings on the curing behavior, cross-linking structure, and thermal and superhigh-frequency dielectric properties of benzoxazine resin. Furthermore, the potential application of this approach in the advanced superhigh-frequency communication field might make progress towards the sustainable development of high-tech polymeric industry.

Sulfuric acid를 도입한 열가소성 폴리우레탄 탄성체의 슬립특성 및 기계적 물성에 관한 연구

We synthesized thermoplastic polyurethane elastomer (TPU) with different contents of sulfuric acid group, and characterized their physical properties such as mechanical, thermal and grip properties. And the results were compared with carboxylic acid-introduced TPU. Wet slip, tensile strength and abrasion properties were increased by the introduction of acid group. Mechanical properties increased with increasing the acid content up to 0.3 wt%. However, wet slip was continually increased as the acid content increased due to increase of hydrophilicity of TPU.

Electroactivity of Polyaniline in High pH Solutions

Generally, the redox activity of polyaniline (PANI) can only be retained in acidic media at pH<4, because the occurrence of deprotonation of the nitrogen atoms in the PANI backbone at high pH values may result in the loss of conduc- tivity and electroactivity in neutral or alkaline solutions. This high acidity requirement greatly limits its potential applications like biosensor, marine antifouling and anticorrosion, where neutral or alkaline environments must be faced. Much effort has been exerted in the development of approaches to overcome this issue. In summary, two principal strategies have been pro- posed to shift the electroactivity of PANI to a high pH environment. One is based on a mechanism of protonic acid doping, the other is based on a charge transfer process. The former is to introduce acidic groups into the PANI chains or PANI sys- tems to hinder the deprotonation of its conducting form and thus to preserve its electroactivity at higher pH values. The main approaches to introduction of acidic groups include the sulfonation of the emeraldine base of PANI, the homopolymerization of aniline derivatives with acidic ionogenic groups or the copolymerization of aniline and aniline derivatives, and the forma- tion of PANI complexes by doping with macromolecular acids. The latter is to use a hybrid film fabricated by incorporating conductive nanomaterials into a PANI matrix, which can improve the charge transfer rate across the PANI matrix and facili- tate its redox processes. The development of PANI nanocomposites prepared by doping with carbon nanotubes, graphenes and Au nanoparticles, etc., falls into this category. This review article provides an overview of various approaches to preserve the electroactivity of PANI in high pH solutions on the basis of the two main strategies. Special emphasis is placed on the synthetic methods and electrochemical features for the self-doped, polymer acid-doped and CNT-doped PANIs, including their underlying mechanisms for achieving good electroactivity. The main challenges and future research directions in this field are also discussed. Keywords polyaniline; electroactivity; high pH values; protonic acid doping; charge transfer

Introduction of acidic groups at the surface of activated carbon by microwave-induced oxygen plasma at low pressure

Functional groups at the surface of a commercial granulated activated carbon were modified at low temperature in an oxygen plasma. Changes in the chemistry of the surface were monitored by thermal desorption, titration of acidic groups, and XPS. A comparison of untreated and plasma-treated carbons, both before and after acid-washing and crushing, showed that reactions in oxygen plasma yield a low surface acidity with minimal modification of the initial sample porosity. Carboxylic groups, which are largely responsible for the surface acidity, appear to be unstable in the presence of the most reactive oxygen species of the plasma.

Alterations of specific and nonspecific binding of monoclonal antibody by introduction of acidic and hydrophobic groups.

AB-6 monoclonal antibody (mAb) against bovine serum albumin (BSA) was coupled with beta-alanine or n-propylamine using a heterobifunctional cross-linking reagent, N-(epsilon-maleimidocaproyloxy)succinimide (EMCS) and a linker, poly-L-cysteine to introduce acidic or hydrophobic groups into the mAb. The mAb molecules coupled with beta-alanine at lower than 1:16 molar ratios and those coupled with n-propylamine at 1:14 retained the original reactivity to BSA but modification with higher amounts of beta-alanine or n-propylamine decreased the reactivity. In contrast, nonspecific bindings of AB-6 mAb to a plastic culture plate and tumor (MDA-MB-453) cells were decreased by modification with beta-alanine and increased by n-propylamine. These results suggested that introduction of acidic groups, and hydrophobic groups to antibody leads to fluctuations in the non-specific binding of antibody.

EFFECTS OF COEXISTING HYDROPHOBIC GROUPS ON ADSORPTION OF DYES ON RAYON FIBERS BEING INTRODUCED ASID GROUPS

In the previous study it has been shown that the introduction of acid groups into the rayon fibers is not effective to increase the fastness to washing.In this study, the effects of hydrophobic groups on the fastness were discussed thermodynami-cally. The effects of the hydrophobic groups and the acid groups when they were coexisting were also discussed similarly.The results obtained are as follows:(1) The affinities and enthalpy changes in the partition (C) type adsorption of the dyes are increased with the hydrophobic group content in the rayon fiber.(2) When the hydrophobic groups and the acid groups coexist, the affinities in the Langmuir's type adsorption of the dye are increased by 2_??_3kcal/mol and the affinities in the C type adsorption of dye are also increased slightly in comparison with the values obtained when only the hydrophobic groups or the acid groups are present.