Trimethylammonium Group Research Articles

Large-pore silica spheres as support for samarium-coordinated undecamolybdophosphate: Oxidative desulfurization of diesels

A novel composite has been prepared through the immobilization of the Keggin sandwich-type [Sm(PMo11O39)2]11− anion (SmPOM) on large-pore silica spheres previously functionalized with trimethylammonium groups (TMA). The resulting SmPOM@TMA-LPMS material has been evaluated as heterogeneous catalyst in a biphasic desulfurization 1:1 diesel/extraction solvent system using H2O2 as oxidant. Preliminary experiments were conducted with different extraction solvents, acetonitrile and [BMIM]PF6 ionic liquid. The optimized extractive and catalytic oxidative desulfurization system (ECODS) with [BMIM]PF6 was able to reach complete sulfur removal from a model diesel containing 2100 ppm S in just 60 min (10 min of initial extraction + 50 min of catalytic step). The reutilization of catalyst and extraction phase has been successfully performed without loss of desulfurization efficiency in consecutive cycles, turning the process more sustainable and cost-effective. The remarkable results with simulated diesel have motivated the application of the catalyst in the desulfurization of untreated real diesel and 74% of efficiency was achieved after only 2 h for three consecutive cycles.

CO2 electrochemical catalytic reduction with a highly active cobalt phthalocyanine

Molecular catalysts that combine high product selectivity and high current density for CO2 electrochemical reduction to CO or other chemical feedstocks are urgently needed. While earth-abundant metal-based molecular electrocatalysts with high selectivity for CO2 to CO conversion are known, they are characterized by current densities that are significantly lower than those obtained with solid-state metal materials. Here, we report that a cobalt phthalocyanine bearing a trimethyl ammonium group appended to the phthalocyanine macrocycle is capable of reducing CO2 to CO in water with high activity over a broad pH range from 4 to 14. In a flow cell configuration operating in basic conditions, CO production occurs with excellent selectivity (ca. 95%), and good stability with a maximum partial current density of 165 mA cm−2 (at −0.92 V vs. RHE), matching the most active noble metal-based nanocatalysts. These results represent state-of-the-art performance for electrolytic carbon dioxide reduction by a molecular catalyst.

Bent Anthracene Dimers as Versatile Building Blocks for Supramolecular Capsules.

This Account provides a comprehensive summary of our 1-decade-long investigations into bent anthracene dimers as versatile building blocks for supramolecular capsules. The investigations initiated in 2008 with the design of an anthracene dimer with a meta-phenylene spacer bearing two substituents on the convex side. Using the bent polyaromatic building block, we began to develop novel supramolecular capsules from two different synthetic approaches. One is a coordination approach, which was pursued by converting the building block into a bent ligand with two pyridine units at the terminal positions. The ligands quantitatively assemble into an M2L4-type capsule through coordination bonding with metal ions. The other is a π-stacking approach, which was followed by utilizing the block as a bent amphiphilic molecule with two trimethylammonium groups at the spacer. In water, the amphiphiles spontaneously assemble into a micelle-type capsule through the hydrophobic effect and π-stacking interactions. Simple modification of the building block allowed us to prepare a wide variety of coordination capsules as well as π-stacking capsules, bearing different hydrophilic side-chains, terminal substitutions, connecting units, polyaromatic panels, or spacer units. The coordination capsule possesses a rigid cavity, with a diameter of ∼1 nm, surrounded by multiple anthracene panels. The spherical polyaromatic cavity binds various synthetic molecules (e.g., paracyclophanes, corannulene, BODIPY, and fullerene C60) in aqueous solutions. With the aid of the polyaromatic shell, photochemically and thermally reactive radical initiators and oligosulfurs are greatly stabilized in the cavity. Biomolecules such as hydrophilic sucrose and oligo(lactic acid)s as well as hydrophobic androgenic hormones are bound by the capsule with high selectivity. In addition, long amphiphilic poly(ethylene oxide)s are threaded into the closed shell of the capsule(s) to generate unusual pseudorotaxane-shaped host-guest complexes in water. In contrast, the π-stacking capsule furnishes a flexible cavity, adaptable to the size and shape of guest molecules, encircled by multiple anthracene panels. In water, the capsule binds hydrophobic fluorescent dyes (e.g., Nile red and DCM) in the cavity. Simple grinding of the bent amphiphile with highly hydrophobic nanocarbons such as fullerenes, nanographenes, and carbon nanotubes (followed by sonication) as well as metal-complexes such as Cu(II)-phthalocyanines and Mn(III)-tetraphenylporphyrins leads to the efficient formation of water-soluble host-guest complexes upon encapsulation. Red emission from otherwise water-deactivated Eu(III)-complexes is largely enhanced in water through encapsulation. Moreover, the incorporation of pH- and photoswitches into the amphiphile affords stimuli-responsive π-stacking capsules, capable of releasing bound guests by the addition of acid and light irradiation, respectively, in water. The host functions of the coordination and π-stacking capsules are complementary to each other, which enables selection of the capsule-type depending on the envisioned target. We are convinced that continued investigation of the present supramolecular capsules featuring the bent anthracene dimer and its derivatives will further increase their value as advanced molecular tools for synthetic, analytical, material, biological, and/or medical applications.

Ionic Polymethacrylate Based Delivery Systems: Effect of Carrier Topology and Drug Loading.

The presented drug delivery polymeric systems (DDS), i.e., conjugates and self-assemblies, based on grafted and star-shaped polymethacrylates have been studied for the last few years in our group. This minireview is focused on the relationship of polymer structure to drug conjugation/entrapment efficiency and release capability. Both graft and linear polymers containing trimethylammonium groups showed the ability to release the pharmaceutical anions by ionic exchange, but in aqueous solution they were also self-assembled into nanoparticles with encapsulated nonionic drugs. Star-shaped polymers functionalized with ionizable amine/carboxylic groups were investigated for drug conjugation via ketimine/amide linkers. However, only the conjugates of polybases were water-soluble, giving opportunity for release studies, whereas the self-assembling polyacidic stars were encapsulated with the model drugs. Depending on the type of drug loading in the polymer matrix, their release rates were ordered as follows: Physical ≥ ionic > covalent. The studies indicated that the well-defined ionic polymethacrylates, including poly(ionic liquid)s, are advantageous for designing macromolecular carriers due to the variety of structural parameters, which are efficient for tuning of drug loading and release behavior in respect to the specific drug interactions.

Kinetics, thermodynamics and mechanisms of phosphate sorption onto bottle gourd biomass modified by (3-chloro-2-hydroxypropyl) trimethylammonium chloride

The sorption kinetics and thermodynamic parameters of phosphate removal from aqueous solution using quaternary ammonium–modified bottle gourd biomass as a sorbent were studied in a batch reactor. The cationic sorbent, containing trimethylammonium and hydroxypropyl groups, was obtained through the chemical reactions of the lignocellulosic Lagenaria vulgaris shell with (3-chloro-2-hydroxypropyl)trimethylammonium chloride. Experimental data of phosphate sorption from aqueous solutions of different initial concentrations (5–140 mg P L−1) have been analysed by reaction kinetics and diffusion models. The characteristic rate constants calculated by linear and non-linear regression analyses of the experimental results are presented. The phosphate sorption reaches equilibrium in 20–30 min, depending on the initial phosphate concentration. The maximum sorption capacity of quaternary ammonium–modified bottle gourd (QABG) sorbent was 18 mg P g−1at 20 oC. The sorption system is best described by a non-linear equation of the pseudo first-order model ( R2 > 0.996). The Weber–Morris model indicated that the sorption process took place in three steps, whereby the intra-particle diffusion is not the only rate-controlling step. In addition, the effect of temperature (20 oC–50 oC) on sorption kinetics was also investigated. The various thermodynamic parameters suggest that phosphate sorption is favoured and is an exothermic process. The activation energy and the sticking probability confirmed that anion exchange is the dominant mechanism. These results provide valuable information for the potential use of agricultural residues in the treatment of wastewaters.

Structural basis of phosphatidylcholine recognition by the C2-domain of cytosolic phospholipase A2α.

Ca2+-stimulated translocation of cytosolic phospholipase A2α (cPLA2α) to the Golgi induces arachidonic acid production, the rate-limiting step in pro-inflammatory eicosanoid synthesis. Structural insights into the cPLA2α preference for phosphatidylcholine (PC)-enriched membranes have remained elusive. Here, we report the structure of the cPLA2α C2-domain (at 2.2 Å resolution), which contains bound 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) and Ca2+ ions. Two Ca2+ are complexed at previously reported locations in the lipid-free C2-domain. One of these Ca2+ions, along with a third Ca2+, bridges the C2-domain to the DHPC phosphate group, which also interacts with Asn65. Tyr96 plays a key role in lipid headgroup recognition via cation-π interaction with the PC trimethylammonium group. Mutagenesis analyses confirm that Tyr96 and Asn65 function in PC binding selectivity by the C2-domain and in the regulation of cPLA2α activity. The DHPC-binding mode of the cPLA2α C2-domain, which differs from phosphatidylserine or phosphatidylinositol 4,5-bisphosphate binding by other C2-domains, expands and deepens knowledge of the lipid-binding mechanisms mediated by C2-domains.

Spectrophotometric determination of choline in pharmaceutical formulations via host-guest complexation with a biomimetic calixarene receptor

Choline is a quaternary ammonium bioactive compound that is used as a dietary supplement. Direct determination of choline in pharmaceutical formulations is a challenging analytical task. The strong UV absorbance of p-sulfonatocalix[4]arene (SC4) and its outstanding complexation properties towards quaternary ammonium compounds have been utilized to develop a method to detect and quantify choline in aqueous solution. This method has been applied to a commercial pharmaceutical choline formulation showing results with no statistically significant difference from those obtained by the official U.S. Pharmacopeial method. The method was validated according to ICH guidelines and the limit of detection for choline was calculated to be 7.2 × 10−6 mol L−1 (1.30 μg mL−1). The host-guest complexation between SC4 and choline were investigated using UV and 1H NMR spectroscopy and DFT calculations. The peak amplitude of the host-guest complexes formed were found to be linearly proportional to the concentration of the choline and l-carnitine analytes in the ranges of 1.0 × 10−5 to 1.6 × 10−4 mol L−1 and 1.0 × 10−5 to 1.8 × 10−4 mol L−1 respectively. The reaction stoichiometry between either choline or l-carnitine with SC4 in the formed complexes were determined to be 1:1 while the stability constants for the complexes formed were estimated to be 8.3 × 104 M−1 and 2.8 × 104 M−1 in the case of choline and l-carnitine, respectively. Both 1H NMR spectroscopy and DFT calculations suggest the complexation between choline and SC4 involves the insertion of the trimethylammonium group of choline into the cavity of SC4 in agreement with previously published X-ray data. The spectrophotometric method presented here should not be limited to the determination of choline. The linear relationship between the peak amplitude of the host-guest complex formed between SC4 and l-carnitine presented here suggests the applicability of the method for the detection of other small molecular species possessing a quaternary ammonium group.

Understanding the mechanism of adsorption of CTAB and polylysine on silver nanoparticles and detection of Hg2+: Experimental and DFT study

Fundamental aspects of poly-l-lysine (PLL) coated silver nanoparticles (AgNPs) are presented for their possible use in colorimetric sensing of heavy metal ions. For this purpose, cetyltrimethylammonium bromide (CTAB) is used, which acts as a stabilizing agent. At the molecular level, the adsorption behavior of PLL and CTAB is evaluated from first principles calculations. These studies demonstrate that PLL and CTAB interact with Ag cluster through NH2 group and positively charged trimethylammonium group, respectively. Surface adsorption of PLL and CTAB on AgNPs is studied under the effect of temperature and reaction time. Multidisciplinary approaches including UV–Visible absorption spectroscopy, Fourier-Transformed Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM) are conducted to systematically investigate PLL coated AgNPs stabilized by CTAB (PL-CT-AgNPs). Thus, a combination of experimental and theoretical analysis helped us to identify specific sites, which promoted such interactions for surface adsorption on AgNPs. As synthesized PL-CT-AgNPs, are found to be highly sensitive and selective towards Hg2+ detection. The mechanism of detection of Hg2+ is studied on PL-CT-AgNPs surface using Density Functional Theory (DFT).

Micellization of selenium-containing cationic surfactants with different headgroups in aqueous solution

Redox-responsive surfactant based on selenium atom has recently attracted considerable interests. Herein, we have designed and synthesized three selenium-containing cationic surfactants with different headgroups, including N-(benzylselanyl-undecyl)-N,N,N-trimethyl ammonium bromide (BSeTAB)/pyridinium bromide (BSePyB)/methylpyrrolidinium bromide (BSeMPB). Their micellization in dilute solution was investigated by surface tension and conductivity, and was related to redox-induced change in molecular structure. Both 1H NMR and ESI-MS spectra demonstrated that selenide in the reduced form is transformed into selenoxide after oxidation with H2O2, whatever the headgroup is. The formation of selenoxide not only increases the hydrophilicity of surfactant, resulting in a more negative $$ \Delta {G}_{\mathrm{ads}}^o $$ , larger cmc, cmc/C20 ratio, and Gmin, compared to the reduced forms, but also provides a new polar headgroup, making it behave like bola-type structure and enhancing the hydrophilicity. The relatively smaller cmc, larger cmc/C20 ratio, and more negative $$ \Delta {G}_m^o $$ value all revealed that the pyridinium or pyrrolidinium polar headgroup is more favorable for the micelle formation than the trimethylammonium group. The thermodynamic parameters showed that the micellization is transformed from entropy-driven mode to enthalpy-driven mode with increasing temperature and the transition temperature at which $$ \Delta {H}_m^o $$ equals to $$ -\mathrm{T}\Delta {S}_m^o $$ is lowest for BSeMPB, and highest for BSePyB.

Morphological and property characteristics of surface-quaternized nanofibrillated cellulose derived from bamboo pulp

In this work, quaternized nanofibrillated cellulose (Q-NFC) was isolated from bamboo bleached kraft pulp through the pre-treatment using 2, 3-epoxy-propyltrimethylammonium chloride (EPTAC) in an aqueous alkaline media and subsequent high-pressure homogenization. A series of aqueous Q-NFC dispersions with different contents of positively charged trimethylammonium groups on the surfaces of fibrils were obtained. With the amount of added EPTAC increased, the solid recovery ratio, surface charge contents, zeta potential values, and extent of nanofibrillation gradually increased for the as-obtained Q-NFCs. TEM images of Q-NFCs revealed that the incorporation of quaternary ammonium groups contributed to the defibrillation into finer nanofibrils with more uniform width distribution. With an increase in the positive charge contents, both degree of polymerization and decomposition temperature of the Q-NFC films decreased slowly. Steady-state rheological result demonstrated that the maximum shear viscosity was achieved for the Q-NFC0.6 dispersion with the medium charge content. The Q-NFC films with higher charge content displayed superior transparency and tensile strength. Furthermore, the oxygen transmission rate of PLA films was remarkably decreased dramatically from 216.0 to 10.3 mL m−2 day−1 after laminating a thin layer of Q-NFC0.6 on the one side. As compared to TEMPO-oxidized NFC from the same pulp, the surface-charged Q-NFC exhibited higher optical transmittance, shear viscosity, and thermal stability as well as comparable oxygen-barrier properties.

Bona fide choline monoxygenases evolved in Amaranthaceae plants from oxygenases of unknown function: Evidence from phylogenetics, homology modeling and docking studies.

Few land plants can synthesize and accumulate the osmoprotectant glycine betaine (GB) even though this metabolic trait has major adaptive importance given the prevalence of drought, hypersaline soils or cold. GB is synthesized from choline in two reactions catalyzed by choline monooxygenases (CMOs) and enzymes of the family 10 of aldehyde dehydrogenases (ALDH10s) that gained betaine aldehyde dehydrogenase activity (BADH). Homolog genes encoding CMO and ALDH10 enzymes are present in all known land plant genomes, but since GB-non-accumulators plants lack the BADH-type ALDH10 isozyme, they would be expected to also lack the CMO activity to avoid accumulation of the toxic betaine aldehyde. To explore CMOs substrate specificity, we performed amino acid sequence alignments, phylogenetic analysis, homology modeling and docking simulations. We found that plant CMOs form a monophyletic subfamily within the Rieske/mononuclear non-heme oxygenases family with two clades: CMO1 and CMO2, the latter diverging from CMO1 after gene duplication. CMO1 enzymes are present in all plants; CMO2s only in the Amaranthaceae high-GB-accumulators plants. CMO2s, and particularly their mononuclear non-heme iron domain where the active site is located, evolved at a faster rate than CMO1s, which suggests positive selection. The homology model and docking simulations of the spinach CMO2 enzyme showed at the active site three aromatic residues forming a box with which the trimethylammonium group of choline could interact through cation-π interactions, and a glutamate, which also may interact with the trimethylammonium group through a charge-charge interaction. The aromatic box and the carboxylate have been shown to be critical for choline binding in other proteins. Interestingly, these residues are conserved in CMO2 proteins but not in CMO1 proteins, where two of these aromatic residues are leucine and the glutamate is asparagine. These findings reinforce our proposal that the CMO1s physiological substrate is not choline but a still unknown metabolite.

Influence of end-group modification on interaction of amphiphilic poly(oxyethylene)-b-poly(oxybutylene) block copolymers with ionic surfactants

Amphiphilic poly(oxyethylene)-b-poly(oxybutylene) block copolymers having hydrophilic block end-capped with neutral dimethylamino (DE79B34) and cationic trimethyl ammonium (TE79B34) groups, respectively were investigated for their interactions with ionic surfactants, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) using tensiometry, conductometry and dynamic light scattering. The self-assembly of DE79B34 and TE79B34 occur at 0.7 g/dm3 and 0.8 g/dm3, respectively. TE79B34 binds favorably with oppositely charged SDS, causing a substantial change in surface tension compared to other surfactant-polymer systems. In mixed polymer-surfactant systems, the micellization was promoted in the presence of SDS, but it was suppressed with CTAB. Such behavior is expected for cationic block copolymers, since they can engage into ion-pair formation with anionic SDS. For neutral polymers, the behavior is reflective of surfactants’ head group hydrophobicity. The head groups of CTAB are more hydrophobic and their existence in the proximity of hydrophobic segments of polymers induces shape transition to non-spherical morphologies. Gibb’s free energy of adsorption at air – water interface is negative for SDS, CTAB and surfactant-block copolymer systems, indicating that the process is highly spontaneous. The increase in entropy of TE79B34 during micelle formation with temperature is due to disturbance of hydrophobic structure of water molecules, thus hydrophobic parts are removed from bulk solution to the interface and also in the interior of micelle the freedom of hydrophobic part is increased. The dynamic laser light scattering results revealed that due to presence of block copolymers pre-micellar aggregates were favored.

Effect of morphology on anion conductive properties in self-assembled polystyrene-based copolymer membranes

Polystyrene (PS) based random and block copolymers with trimethylammonium and azide side groups are synthesized via nitrogen mediated living radical polymerization. Anion exchange membranes (AEMs) are fabricated from the synthesized copolymers with hydrophobic and hydrophilic dialkyne crosslinkers using Click reaction. Morphological analysis by SAXS and TEM reveals the formation of ordered spherical nanostructure in the block copolymer membranes. In comparison with AEMs from the random copolymer, the block membranes show superior conductivity in higher KOH solutions despite their lower original IEC. The highest conductivity is obtained in 3 M KOH. No significant increase of water absorption or swelling is observed at elevated temperatures for any of the membranes, indicating their good mechanical integrity. No physical degradation is observed for the block membranes after 63 days in 8 M KOH at 60 °C. Fuel cell testing reveals that the block copolymer membranes with well-ordered nanostructure maintained better performance after 10 polarization curves compared to the commercially available AEM (A201).

Modulating cell response on cellulose surfaces; tunable attachment and scaffold mechanics

Combining surface chemical modification of cellulose to introduce positively charged trimethylammonium groups by reaction with glycidyltrimethylammonium chloride (GTMAC) allowed for direct attachment of mammalian MG-63 cells, without addition of protein modifiers, or ligands. Very small increases in the surface charge resulted in significant increases in cell attachment: at a degree of substitution (DS) of only 1.4%, MG-63 cell attachment was > 90% compared to tissue culture plastic, whereas minimal attachment occurred on unmodified cellulose. Cell attachment plateaued above DS of ca. 1.85% reflecting a similar trend in surface charge, as determined from ζ-potential measurements and capacitance coupling (electric force microscopy). Cellulose film stiffness was modulated by cross linking with glyoxal (0.3–2.6% degree of crosslinking) to produce a range of materials with surface shear moduli from 76 to 448 kPa (measured using atomic force microscopy). Cell morphology on these materials could be regulated by tuning the stiffness of the scaffolds. Thus, we report tailored functionalised biomaterials based on cationic cellulose that can be tuned through surface reaction and glyoxal crosslinkin+g, to influence the attachment and morphology of cells. These scaffolds are the first steps towards materials designed to support cells and to regulate cell morphology on implanted biomaterials using only scaffold and cells, i.e. without added adhesion promoters.

ICP-2: A New Hybrid Organo-Inorganic Ferrierite Precursor with Expanded Layers Stabilized by π–π Stacking Interactions

In this work we present the synthesis, characterization, and molecular modeling of ICP-2, a new layered ferrierite precursor with expanded layers. ICP-2 is obtained in fluoride medium from aluminosilicate gels with low H2O content, using the chiral cation (1R,2S)-dimethylephedrinium (DMEP) as the organic structure-directing agent; ICP-2 can also be obtained as the Al-free form. The combination of physicochemical characterization of the material with molecular modeling indicates that ICP-2 is a layered material composed of ferrierite layers, where the organic cations play a dual structural role through the formation of supramolecular aggregates. On one hand, the organic cations stabilize the formation of the ferrierite layers with a core–shell structure, directing the formation of both the pseudo-10R channels (by supramolecular dimers aligned with the channel direction) and of the pseudocavities, with the trimethylammonium groups of DMEP fitting within. On the other hand, the aromatic rings of these organi...

Tuning the position of head groups by surfactant design in mixed micelles of cationic and carbohydrate surfactants

HypothesisEmerging applications of carbohydrate/cationic surfactant mixtures require not only synergistic mixing, but also accessible sugar headgroups at the exterior of micelles. A previous study showed that the glucoside headgroups of octyl-β-d-glucopyranoside aggregate at the interior of mixed micelles with equimolar cetyltrimethylammonium bromide rather than mixing with trimethylammonium groups at the corona. The current study tests the hypothesis that structural characteristics of the surfactants (the relative lengths of the alkyl tails and the type of linker) can be tuned to shift the carbohydrate groups to micelle surfaces. ExperimentsThe structural arrangement of 30 mM equimolar mixed micelle solutions in D2O is investigated using NMR. The dynamics in different regions are probed using 1H spin-lattice (T1) and spin-spin (T2) relaxation measurements, and relative positioning by nuclear Overhauser effect spectroscopy (NOESY). Additional micellar properties are determined using solvatochromic fluorescent probes. FindingsMatching surfactant alkyl tail lengths is found ineffective at “pushing out” the carbohydrate headgroups due to a large mismatch in interactions between the headgroups and D2O. However, inserting a novel polar triazole group between the carbohydrate head group and the hydrophobic tail (e.g. in n-octyl-β-d-xylopyranoside) using click chemistry is able to “pull out” the carbohydrate, thus giving accessible sugar moieties at the surface of mixed micelles.

Effect of Ionic Strength and Surface Charge Density on the Kinetics of Cellulose Nanocrystal Thin Film Swelling.

This work explores cellulose nanocrystal (CNC) thin films (<50 nm) and particle-particle interactions by investigating film swelling in aqueous solutions with varying ionic strength (1-100 mM). CNC film hydration was monitored in situ via surface plasmon resonance, and the kinetics of liquid uptake were quantified. The contribution of electrostatic double-layer forces to film swelling was elucidated by using CNCs with different surface charges (anionic sulfate half ester groups, high and low surface charge density, and cationic trimethylammonium groups). Total water uptake in the thin films was found to be independent of ionic strength and surface chemistry, suggesting that in the aggregated state van der Waals forces dominate over double-layer forces to hold the films together. However, the rate of swelling varied significantly. The water uptake followed Fickian behavior, and the measured diffusion constants decreased with the ionic strength gradient between the film and the solution. This work highlights that nanoparticle interactions and dispersion are highly dependent on the state of particle aggregation and that the rate of water uptake in aggregates and thin films can be tailored based on surface chemistry and solution ionic strength.

Positive-Charge Functionalized Mesoporous Silica Nanoparticles as Nanocarriers for Controlled 2,4-Dichlorophenoxy Acetic Acid Sodium Salt Release.

Because of its relatively high water solubility and mobility, 2,4-dichlorophenoxy acetic acid (2,4-D) has a high leaching potential threatening the surface water and groundwater. Controlled release formulations of 2,4-D could alleviate the adverse effects on the environment. In the present study, positive-charge functionalized mesoporous silica nanoparticles (MSNs) were facilely synthesized by incorporating trimethylammonium (TA) groups onto MSNs via a postgrafting method. 2,4-D sodium salt, the anionic form of 2,4-D, was effectively loaded into these positively charged MSN-TA nanoparticles. The loading content can be greatly improved to 21.7% compared to using bare MSNs as a single encapsulant (1.5%). Pesticide loading and release patterns were pH, ionic strength and temperature responsive, which were mainly dominated by the electrostatic interactions. Soil column experiments clearly demonstrated that MSN-TA can decrease the soil leaching of 2, 4-D sodium salt. Moreover, this novel nanoformulation showed good bioactivity on target plant without adverse effects on the growth of nontarget plant. This strategy based on electrostatic interactions could be widely applied to charge carrying agrochemicals using carriers bearing opposite charges to alleviate the potential adverse effects on the environment.

Hydra amphiphiles: Using three heads and one tail to influence aggregate formation and to kill pathogenic bacteria

Hydra amphiphiles mimic the morphology of the mythical multi-headed creatures for which they are named. Likewise, when faced with a pathogenic bacterium, some hydra derivatives are as destructive as their fabled counterparts were to their adversaries. This report focuses on eight new tricephalic (triple-headed), single-tailed amphiphiles. Each amphiphile has a mesitylene (1,3,5-trimethylbenzene) core, two benzylic trimethylammonium groups and one dimethylalkylammonium group with a linear hydrophobe ranging from short (C8H17) to ultralong (C22H45). The logarithm of the critical aggregation concentration, log(CAC), decreases linearly with increasing tail length, but with a smaller dependence than that of ionic amphiphiles with fewer head groups. Tail length also affects antibacterial activity; amphiphiles with a linear 18 or 20 carbon atom hydrophobic chain are more effective at killing bacteria than those with shorter or longer chains. Comparison to a recently reported amphiphilic series with three heads and two tails allows for the development of an understanding of the relationship between number of tails and both colloidal and antibacterial properties.

High Hydroxide Ion Conductivity with Enhanced Alkaline Stability of Partially Fluorinated and Quaternized Aromatic Copolymers as Anion Exchange Membranes

For enhancing hydroxide ion conductivity, alkaline stability, and fuel cell performance of quaternaized aromatic/perfluoroaklyl copolymer (QPAF) membranes, ammonium groups attached to the polymer backbone have been investigated. The ammonium groups included dimethylbutylamine (DMBA), dimethylhexylamine (DMHA), and 1,2-dimethylimidazole (DMIm) groups in comparison to the trimethylammonium (TMA) group. DMBA turned to be the optimum ammonium group for QPAF membranes in terms of its high hydroxide ion conductivity based on well-connected and larger phase-separated morphology than that of QPAF-TMA with similar ion exchange capacity (IEC) value. QPAF-DMBA (IEC = 1.33 mequiv g–1) exhibited the highest hydroxide ion conductivity among the tested membranes up to 152 mS cm–1 in water at 80 °C, which was 1.6 times higher than that of QPAF-TMA (95 mS cm–1). In addition, QPAF-DMBA exhibited reasonable alkaline stability in 1 M KOH at 60 °C for 1000 h. The remaining conductivity was 44 mS cm–1 (58%) for QPAF-DMBA, whil...