Polycations. III. Synthesis of polyphosphonium salts for use as antibacterial agents

Several series of polyphosphonium salts have been prepared. These include those in which the cationic sites are located at regular intervals along a linear chain of defined length (“strings”) and those in which the cationic sites are in linkages arrayed in branching arms about a central focus unit (“balloons”). Similarly, polyphosphonium balloon arrays have been attached to a polystyrene backbone providing a material that can serve as an anionic exchange resin. Several of the resultant materials have demonstrated antibacterial activity, in systems analogous to those previously reported for simple functionalized polystyrene species, and continue to be investigated. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:495–502, 1998     

The effect of aluminium compounds in the copolymerization of ethylene / α-olefins

Two types of copolymerizations were found with the catalyst system Cp₂ZrCl₂/MAO. One was a less exothermic reaction, and another was a more exothermic one. The former provided a polymer with a single composition distribution because of a single cationic active site. The latter provided a polymer with a bimodal composition distribution, indicating the existence of two active sites. The two active sites were investigated through the comparison of MAO systems and alkylaluminium / borate systems. We speculated that the two active sites were the normal cationic site and the active site where the interaction between a cationic metallocene and an aluminium compound was strong.     

Electroosmotic flow in template-prepared carbon nanotube membranes.

Carbon nanotube membranes (CNMs) were prepared by doing chemical vapor deposition of carbon within the pores of a microporous alumina template. Electroosmotic flow (EOF) was driven across the CNMs by allowing the membrane to separate two electrolyte solutions and using an electrode in each solution to pass a constant ionic current through the nanotubes. EOF was investigated by measuring the flux of a probe molecule (phenol) across the CNM. The as-synthesized CNMs have anionic surface charge, and EOF is in the direction of cation migration across the membrane. Measurements of the rate of EOF as a function of applied transmembrane current provided the zeta potential. The effect of pH on zeta provided the pK(a) for the surface acidic sites responsible for this anionic charge; the acidic-site density was also determined. An electrochemical derivatization method was used to attach carboxylate groups to the nanotube walls; this enhances the anionic surface charge density, resulting in a corresponding increase in the EOF rate. Electrochemical derivatization was also used to attach cationic ammonium sites to the nanotube walls to yield CNMs that show EOF in the opposite direction of the as-synthesized or carboxylated membranes.     

META 4. Prediction of the metabolism of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in the environment and are often implicated as potential carcinogens. It is generally believed that the carcinogenic potential of polycyclic aromatic hydrocarbons is linked to the formation of ultimate carcinogens generated by metabolic biotransformations. In this paper we propose a methodology that consists of using both quantum chemical properties and structural features of the reaction sites to predict PAH metabolism. Two essential questions have been answered: at which sites will the reaction take place and does the transformation consist of epoxidation or hydroxylation? This methodology has been successfully implemented into an expert system, META, for the evaluation of metabolic transformations of new chemicals. Received: 3 April 1998 / Accepted: 6 July 1998 / Published online: 7 October 1998     

Transformation of the cationic growing center of poly(tetrahydrofuran) into an anionic one by bis(pentamethylcyclopentadienyl)samarium

Transformation of the cationic growing center of living poly(tetrahydrofuran) [poly(THF)] into an anionic one was achieved in high efficiency (62%) by the end-capping of living poly(THF) with potassium iodide followed by the reduction with bis(pentamethylcyclopentadienyl)samarium (Cp*₂Sm), whereas the direct reduction with Cp*₂Sm without the end-capping resulted in the formation of poly(THF) with pentamethylcyclopentadienyl group at the terminal. The increase in the molecular weight of poly(THF) after the reduction was observed, which indicates the presence of the dimerization of poly(THF) during the reduction. The polymerization of a variety of electrophilic monomers including δ-valerolactone, 2-oxo-1,3-dioxane, and alkyl methacrylates with the macroanion provided good yields of the corresponding block copolymers consisting of both cationically and anionically polymerizable monomers. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2209–2214, 1998     

Resonance Rayleigh scattering for the determination of cationic surfactants with Eosin Y

Resonance Rayleigh scattering (RRS) of cationic surfactants–Eosin Y systems and their analytical application have been studied. In aqueous solution at pH 2∼3, Eosin Y reacts with a monomer of cationic surfactants (CS), such as Zephiramine (Zeph), tetradecylpyridinium bromide (TPB), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC) and cetyltrimethylammonium bromide (CTMAB), to form an ion associate and a new RRS spectrum appears. The spectral characteristics of the five ion associates are similar and their maximum scattering wavelengths (λ_max) are all at 313 nm. The intensity of RRS at λ_max of the ion associate is directly proportional to the concentration of CS in the range of 0∼3.0 μg/25 mL. The technique has high sensitivity for the determination of CS; their detection limit is between 5.57 ng/mL and 7.60 ng/mL depending on the CS. In this case, most metal and non-metal ions, NH₄ ⁺ and some anionic surfactants do not interfere, so that the method has a good selectivity. It can be applied to the determination of trace amounts of cationic surfactants in water samples. Received: 9 September 1998 / Revised: 17 November 1998 / Accepted: 18 November 1998     

Construction,Enzyme Response,and Substrate Capacity of a Hyaluronan–Cyclodextrin Supramolecular Assembly

A supramolecular assembly was constructed with a cationic cyclodextrin (EICD) and native hyaluronan (HA). The cationic carboxylic ester pendants on HA support hyaluronidase (HAase)‐responsive sites and the EICD supports artificial carboxylic esterase responsive sites. Substrate‐binding models were investigated by using environment‐sensitive fluorescence probes 2‐p‐toluidino‐6‐naphthalenesulfoniate sodium (2,6‐TNS) and thioflavin T (ThT). On a HA/EICD assembly, EICD was able to bind an anionic substrate and HA and EICD constructed the cationic substrate binding site together. This assembly could be used as a sequential dual‐substrate carrier.     

Synthesis of polystyrene-based cationic copolymers and their colloidal properties in water

A series of polystyrene-based cationic copolymers was synthesized by two different methods: (1) solution copolymerization of styrene and vinylbenzyl trimethylammonium chloride (VBTMAC) in ethanol, and (2) surfactant-free emulsion copolymerization of styrene and vinylbenzyl chloride in water followed by reaction with trimethylamine. The results indicated that the different synthesis methods would result in different polymer structures and, therefore, affect the solubility and colloidal properties of the copolymers in water. For the copolymers prepared by method 2, partial crosslinking was observed. The copolymers made by this method are almost water-insoluble. In contrast, the copolymers made from direct copolymerization of styrene and VBTMAC in ethanol are water-soluble or dispersible, but the solubility and the particle size of microaggregates formed by these copolymers in water strongly depend on charge density and temperature. One of the important results from this study is that uniform colloidal particles with a very small particle size (30–50 nm) can be obtained by dispersing polystyrene-based cationic copolymers in water without adding any surfactants. Received: 29 July 1998 Accepted in revised form: 28 September 1998     

Synthesis of Biological Activities of Phosphorus-Containing Polycationic Strings

Abstract

Several series of phosphoruscontaining polycationic strings have been prepared. These include those in which quaternary phosphonium sites are located at regular intervals along a linear chain of defined length (“Strings”), and those in which the cationic phosphonium, sites are in linkages arrayed in branching arms about a cenhal focus unit (“baloons”). Polyphosphonium “balloon” arrays have been attached to a polystyrene backbone prowding a mataial which serves as an anionic exchange resin. PolyCationic strings have been prepared in which phosphorus is present a3 phosphine oxide functidties and the cationic sites are quatanary ammonium sites anayed at regular intervals along a linear chain of defined length. Several of the resultant materials have demonshated sigruficant antibaaaial activity. Interactions of the polycationic species with the anionic gmove region of double stranded DNA have been investigated.     

Interactions between polyampholytes and ionic surfactants

The interactions of two partially charged ampholytic terpolymers [consisting of acrylamide, sodium 2-acrylamido-2-methylpropanesulphonate, and 2-(methacryloyloxyethyl)trimethylammonium chloride segments with molar compositions 80/12/08 and 80/08/12] and two fully charged ampholytic copolymers (containing only the two latter comonomers with molar compositions of 80/20 and 50/50), with cationic surfactants [tetradecyl- trimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB)] and the anionic surfactant sodium dodecylsulphate (SDS), are investigated. The studies include phase behaviour (swelling, solubilisation, precipitation), viscometry, electrical conductivity, and potentiometry (bromide ion and surfactant ion-specific electrodes). The 80/08/12 and 80/12/08 polyampholytes swell in water and are solubilised in the presence of cationic or anionic surfactants above a particular surfactant concentration that is proportional to the polymer concentration. The polyampolyte 80/20 is soluble in water but precipitates in the presence of TTAB, whereas 50/50 is insoluble in water and in the presence of TTAB, but is solubilised upon addition of SDS. The results indicate that TTAB binds to 80/12/08 with little or no cooperativity. Solubilisation appears to be the result of the increasing polyelectrolyte character of the polyampholyte upon neutralisation of its charged sites by bound surfactant ions of opposite charge. The binding of TTAB by the 50/50 polyampholyte is very weak and non-cooperative. In contrast, 80/20 binds TTAB cooperatively, much like a true polyelectrolyte-surfactant system of opposing charges. In particular, the binding is characterised by the existence of a critical aggregation concentration. A partial phase diagram for this system has been determined from the TTA⁺-electrode potential data. The behaviour of true polyelectrolytes and polyampholytes, with respect to their interaction with surfactants, is discussed. Received: 22 July 1998 Accepted: 14 September 1998     

Adsorption of CO on oxygen preadsorbed neutral and charged gas phase Pd4 clusters: A density functional study

We present the results of a density functional calculation on adsorption of O₂, CO, and their coadsorption at various sites of neutral, cationic, and anionic Pd₄ clusters. For all the clusters, the dissociative adsorption of oxygen sitting on Pd bridge sites is found to be preferable. Both O₂ and CO binding energies are found to be higher for the anionic Pd₄ cluster followed by cationic and neutral cluster. However, binding energies of O₂ or CO in the coadsorption complexes follow the trend: anionic > neutral > cationic. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Grafting polyelectrolytes onto polyacrylamide for flocculation 2. Model suspension flocculation and sludge dewatering

Low-molecular-weight high-charge-density cationic poly(diallyldimethylammonium chloride) (polyDADMAC) was grafted onto high-molecular-weight nonionic polyacrylamide (PAM) via a free radical mechanism using a gamma radiation technique. The graft copolymers having various charge densities were evaluated as flocculants for titanium dioxide (TiO₂) model suspensions, and as conditioners for a pulp and paper mill sludge. Their flocculation performance was optimized with respect to polymer composition, gamma irradiation time and polymer dosage. Measurements included turbidity, particle size distribution and drainage rates. The graft copolymers showed a significant improvement over the homopolymers and dual polymer systems in their flocculation and sludge dewatering performance. Received: 6 April 1998 Accepted in revised form: 28 August 1998     

Interfacial and micellar properties of some anionic/cationic binary surfactant systems. 1. Surface properties and prediction of surface tension

The surface tension equations of binary surfactant mixtures are established by combining the Szyszkowski equation for pure surfactant solutions and extended nonideal theory for mixed adsorption. They are then successfully applied to two relatively long-chain anionic/cationic binary surfactant systems: triethanolammonium dodecylpoly(oxyethylene)sulfate, as an anionic species (containing about 2 ethylene oxide units), mixed with dodecyltrimethylammonium bromide or hexadecyltrimethylammonium bromide. The composition of the mixed monolayer is mixing-ratio dependent and is slightly asymmetric: for overall equimolar mixtures, the larger mole fraction in the mixed monolayer is that of the more surface-active ion. The strong synergetic effects observed in the surface tension reduction efficiency are reflected by large negative β^s parameters, according to regular solution theory. They can be interpreted by the more negative adsorption free energy of each surfactant and the smaller area occupied by surfactant hydrocarbon chains in the mixed monolayer. Received: 20 April 1998 /Accepted in revised form: 27 August 1999     

Grafting polyelectrolytes onto polyacrylamide for flocculation 1. Polymer synthesis and characterization

Low-molecular-weight high-charge-density cationic diallyldimethylammonium chloride homopolymer (polyDADMAC) was grafted onto high-molecular-weight nonionic polyacrylamide (PAM) via a free radical mechanism using a gamma radiation technique. The graft copolymer systems were characterized in terms of viscosity, composition, gel content, degree of grafting and grafting efficiency. Degree of grafting was a strong function of radiation dose, dose rate and polyelectrolyte concentration. Gels were formed at high radiation doses and high PAM levels. Crosslinking between the electrolyte polymers was limited due to electrostatic repulsion. Gelation was mainly caused by coupling of PAM chains. High grafting efficiency was achieved: the lower the poly(DADMAC) concentration, the higher the grafting efficiency observed. The grafting mechanism and the effect of ion interactions on copolymer structural properties are also elucidated and discussed. Received: 6 April 1998 Accepted in revised form: 28 August 1998     

Which are the mechanisms governing in cationic emulsion polymerization?

The cationic emulsion polymerization of styrene in a batch reactor using different concentrations of dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethyl-ammonium bromide (HDTAB) as cationic surfactants, and 2,2′-azobisisobutyramidine dihydrochloride (AIBA), and 2,2′-azobis (N,N′-dimethyleneisobutyramidine) dihydrochloride (ADIBA) as cationic initiators has been studied. In the preliminary study, the best conditions to obtain stable cationic latexes at high conversions were identified. When the surfactant concentration was above its cmc, latexes with high conversions were achieved for the two cationic surfactants studied (DTAB and HDTAB). Cationic latexes with less coagulum were obtained using ADIBA as cationic initiator due to its superior resistance to hydrolysis. AIBA is hydrolyzed to amide at basic pHs and in this way, the concentration of radicals formed in the aqueous phase decreases. On the other hand, a stronger effect of the particle size on the kinetics of the cationic emulsion polymerization of styrene using HDTAB as cationic surfactant was observed than using DTAB. Furthermore, different kinetic behaviors were observed with the two cationic initiators (ADIBA and AIBA) using HDTAB as cationic surfactant, due to the lower stabilizing effect of the cationic radicals provided by AIBA.     

Synthesis of sulfur-containing cationic lipids of the 1,3-dioxolane type

A series of cationic acetal lipids containing different spacer and cationic groups were synthesized starting from 1,2-O-hexadecylidene-3-thioglycerol. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1590–1592, August, 1998.     

Affinity monolithic capillary columns for glycomics/proteomics: 1. Polymethacrylate monoliths with immobilized lectins for glycoprotein separation by affinity capillary electrochromatography and affinity nano-liquid chromatography in either a single column or columns coupled in series

In this report, microcolumn separation schemes involving monolithic capillary columns with immobilized lectins, and relevant to nanoglycomics/nanoproteomics were introduced. Positive and neutral monoliths based on poly(glycidyl methacrylate-co-ethylene dimethacrylate) were designed for achieving lectin affinity chromatography (LAC) by nano-LC and CEC. The positive monoliths (i.e., monoliths with cationic sites) afforded relatively high permeability in nano-LC but lack predictable EOF magnitude and direction, while neutral monoliths provided a good compromise between reasonable permeability in nano-LC and predictable EOF in CEC. Lectin affinity nano-LC permitted the enrichment of classes of different glycoproteins having similar N-glycans recognized by the immobilized lectin, whereas lectin affinity CEC provided the simultaneous capturing and separation of different glycoproteins due to differences in charge-to-mass ratio. Also, this investigation demonstrated for the first time the coupling of lectin capillary columns in series (i.e., tandem columns) for enhanced separation of glycoproteins by LAC using the CEC modality. Furthermore, in the coupled columns format, glycoforms of a given glycoprotein were readily separated.     

Photophysical and rheological properties of naphthalene-labeled cationic poly(dimethyl sulfate quaternized acrylamide/N,N-dimethylaminopropylmaleimide copolymer)

The synthesis, rheological, and fluorescence properties of a cationic water-soluble copolymer, naphthalene-labeled cationic poly(dimethyl sulfate quaternized acrylamide/N,N-dimethylaminopropylmaleimide copolymer), poly(DSQADMAPM)/NA, are reported. When fluorescent hydrophobes (naphthyl group) are incorporated into the cationic copolymer, the photophysical response may effectively probe solution behavior on the microscopic level. The salt and pH responsiveness inherent to the cationic copolymer systems is a function of ionic group type. Experimental results indicate that I_E/I_M increases steadily with increases in polymer concentration and I_E/I_M values for a given polymer concentration are higher in salt. At low pH values, I_E/I_M is high and excimer emission increases as the quaternary amino groups (R₄N⁺) are screened out. Dynamic light scattering (QELS) measurements indicate that diffusion coefficients of the cationic copolymer increase and the hydrodynamic diameters decrease with increasing salt concentration. Viscosity studies reveal that the polymer coil shrinks as salt is added. In fluorescence quenching study, the reduction in the quenching efficiency of thallium (Tl⁺) with salt addition can arise from enhanced compartmentalization of naphthalene labels as added electrolyte enhances intrapolymer micellization. The intrapolymer micelle is easily formed, indicating that the thallium ion has difficulty in reacting with bound naphthalenes located in the shrunk polymer coil. The cationic copolymer is depicted as an expanded polymer coil in deionized water because of intra- and interchain repulsions. Consequently, salt addition breaks down the repulsions and enhances intrapolymer micellization. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 11–19, 1998     

In situ PEI and formic acid directed formation of Pt NPs/MWNTs hybrid material with excellent electrocatalytic activity

A hybrid material based on Pt nanoparticles (Pt NPs) and multi-walled carbon nanotubes (MWNTs) was fabricated with the assistance of PEI and formic acid. The cationic polyelectrolyte PEI not only favored the homogenous dispersion of carbon nanotubes (CNTs) in water, but also provided sites for the adsorption of anionic ions PtCl₄²⁻ on the MWNTs’ sidewalls. Deposition of Pt NPs on the MWNTs’ sidewalls was realized by in situ chemical reduction of anionic ions PtCl₄²⁻ with formic acid. The hybrid material was characterized with TEM, XRD and XPS. Its excellent electrocatalytic activity towards both oxygen reduction in acid media and dopamine redox was also discussed.     

Theoretical models for activation of CO2 towards hydration (CO2 + H2O → H2CO3) by cationic binding sites

Theoretical models are studied which illustrate how the hydration reaction CO₂ + H₂O → H₂CO₃ can be catalysed by one or two cationic binding sites (NH₄⁺). In the latter, the arrangement of the two bindings sites is held during the course of the reaction, simulating a rigid molecular receptor. Two different arrangements of the binding sites are studied, and their relative abilities to lower the activation energy of the hydration reaction are studied.