Catalytic effect of poly(4-vinyl-N-alkylpyridinium) salts on the hydrolysis of ester- and amide-containing indolyl groups

Alkaline hydrolyses of p-nitrophenyl-3-indoleacetate (p-NPIA) and N-(indole-3-acryloyl)imidazole (IAI) were studied in the presence of poly(4-vinyl-N-propylpyridinium bromide) (C3PVP), poly(4-vinyl-N-benzylpyridinium chloride) (BzPVP), and copolymers of 4-vinyl-N-benzylpyridinium chloride and 4-vinyl-N-cetylpyridinium bromide (C16BzPVP). The hydrolyses were enhanced by the addition of these cationic polyelectrolytes. The magnitudes of the enhancement were in the order C16BzPVP > BzPVP > C3PVP, which is explainable in terms of the hydrophobicity of the polymers. The result and activation parameters obtained indicated that the substrates bound to polymers were more reactive than free substrates. The association constants obtained from the kinetic measurements (K) increased in the order BzPVP < C3PVP < C16BzPVP, which may suggest an important contribution of charge transfer interaction, in addition to electrostatic and hydrophobic interactions, between the polymers and the substrates. The association constants between the polymers and IAI were also obtained independently from the spectrophotometric measurements (K^*) with the charge transfer absorption bands. The lack of a satisfactory agreement between K and K^* is discussed.     

Synchronous multilayered adsorption of macrocations and macroanions on colloidal spheres. Influence of foreign salt and basicity or acidity of the macroions

The influence of foreign salt, the basicity or the acidity of macroions and the equivalency of the number of ionic groups of macrocations and macroanions upon alternate multiple adsorption on surfaces of colloidal silica (CS91, 110 nm in diameter) and polystyrene spheres (D1A19, 220 nm) have been studied by electrophoretic light scattering measurements. The macrocations used were poly(4-vinyl-N-n-butyl pyridinium bromide (C4PVP, strongly basic), poly(4-vinyl-N-ethyl pyridinium bromide (C2PVP, strongly basic) and poly(allylamine) (PAL, weakly basic). Sodium poly(styrene sulfonate) (NaPSS, strongly acidic) and sodium polyacrylate (NaPAA, weakly acidic) were used as macroanions. The alternate adsorption disappears even in the presence of a small amount of sodium chloride. The alternate multiple adsorption takes place on the addition of C4PVP first and NaPSS next, PAL first and NaPAA next, NaPAA first and C4PVP next, and NaPAA first and PAL next on the CS91 spheres. The influence of the equivalency of the number of ionic groups of C2PVP and NaPAA has been studied for the adsorption on the D1A19 spheres. The synchronous delicate balancing of the electrostatic interactions among the macrocations, the macroanions and the surfaces of the colloidal spheres is important for the alternate multiple adsorption.     

Drying dissipative patterns of aqueous solutions of poly (4-vinyl-N-alkyl-pyridinium halide)

Drying dissipative structural patterns of aqueous solutions of poly (4-vinyl-N-alkyl-pyridinium halide) were studied on a cover glass. The broad rings were observed at the outside edge of the dried film. The broad ring size (or the area of the dried film, S) increased as polymer concentration increased. The broad ring size decreased and then turned to increase when the hydrophobicity of the polymers increased. The drying time from the initial liquid (T) was insensitive to the polymer concentration. But, T was sensitive to the kind of polymers, i.e., hydrophobicity of polycations, and roughly in the opposite order to that of S. Spoke-like macroscopic patterns appeared clearly for poly (4-vinyl-N-n-butylpyridinium bromide) (C4PVP), but were not observed clearly for the other polymers. Cross-like microscopic patterns appeared from which the polymers with the extended conformation are deduced to be crystallized during the course of dryness. The cooperative crystallization took place between the polymer and the salt in the C4PVP + KCl mixtures. When two different polymers were mixed, segregation and then independent crystallization of each single component polymers were observed. The dissipative effect is important for determining of the polymer crystal structure during the course of crystallization.     

Polyelectrolytes containing dihydronicotinamide. III. Fluorescence quenching by nicotinamide-containing polymers in aqueous solution

Charge-transfer (CT) interaction of N-benzyl-1,4-dihydronicotinamide (BNAH) and poly(sodium styrene-p-sulfonate) containing 6 mol % of BNAH groups (PNAH) with several types of nicotinamide-containing polyelectrolytes in aqueous solution was investigated by fluorescence quenching. The experimental data were analyzed in terms of a kinetic model including both static and dynamic quenching. Hydrophobic association of BNAH with the polymers led to more effective quenching than the monomer [N-benzylnicotinamide (BNA)] system. Electrostatic attraction of PNAH and BNA also resulted in the remarkably large value of apparent quenching constant (K′ = 1.4 × 10⁴M^?1). Further, the fluorescence of PNAH was quenched far more effectively by poly[N-(p-vinylbenzyl)nicotinamide] (PBNA) and poly(acrylamide)s containing nicotinamide (NA) groups (PAm) due to the formation of a polyelectrolyte complex (PEC). In this case, the K′ value depended on the BNA content in the copolymer, suggesting the structural matching effect of the interacting pair on the intermacromolecular interaction.     

Mg/Na selectivity of sulfonic cation-exchange membrane modified with poly(4-vinyl-N-propylpyridinium) bromide

Mg/Na selectivity of sulfonic cation-exchange membrane modified with poly(4-vinyl-N-propylpyridinium) bromide by surface electrodeposition, influenced by the electrodialysis conditions, is studied.     

Effect of nonpolar field formed by polymer ligand on the oxidation of 2,6-xylenol catalyzed by Cu complexes

The oxidative polymerization catalyzed by Cu(II)-poly(vinylpyridine) derivatives and the effect of the nonpolar field formed by the polymer ligand on the catalysis was studied in dimethyl sulfoxide (DMSO) solvent. The catalytic activity of the Cu complex increases in the following order; Cu-(styrene-vinylpyridine copolymer) (St·VP) complex > Cu-partially quarternized (by benzyl chloride) poly(vinylpyridine)(BCQP) complex > Cu-poly(vinylpyridine) (PVP) complex > Cu-pyridine (Py) complex > Cu-partially quarternized (by ethyl bromide) poly(vinylpyridine) (EBQP) complex. This order is the same as that of the reoxidation rate constant of the catalyst. Acceleration of k_o process in Cu-St>VP and Cu-BCQP systems, where the active site is in the nonpolar field formed by the polymer ligand, is explained by an increase in strength of the coordination bonds.     

Synthesis of Polycyclic Tertiary Carbinamines by Samarium Diiodide Mediated Cyclizations of Indolyl Sulfinyl Imines

Samarium diiodide mediated cyclizations of N‐acylated indole derivatives bearing sulfinyl imine moieties afforded polycyclic tertiary carbinamines with moderate to excellent diastereoselectivities. Lithium bromide and water turned out to be the best additives to achieve these transformations in good yields. Using enantiopure sulfinyl imines the outcome strongly depends on the reactivity of the indole moiety. Whereas with unactivated indole derivatives desulfinylation and formation of racemic products was observed, indoles bearing electron‐withdrawing substituents at C‐3 afforded the polycyclic products with intact N‐sulfinyl groups and with excellent diastereoselectivity, finally allowing the preparation of enantiopure tertiary carbinamines. The mechanisms of these processes are discussed.     

Structure and properties of complexes formed by cationic polymers and anionic cholesterol-containing liposomes

The adsorption of the synthetic polycation poly(N-ethyl-4-vinylpyridinium bromide) on the surface of three-component lipid vesicles (liposomes) formed from a mixture of anionic cardiolipin, electroneutral egg lecithin, and nonionic cholesterol is studied via laser microelectropheresis, dynamic light scattering, conductometry, fluorescence spectroscopy, and UV spectroscopy. The incorporation of cholesterol into the liposomal membrane increases its microviscosity; however, the membrane remains liquid-crystalline. Simultaneously, an increase in the fraction of cholesterol causes the formation of defects in liposome membranes during their binding with poly(N-ethyl-4-vinylpyridium bromide) and makes complexation irreversible. The results of this study are of interest for predicting the behavior of polyelectrolytes and biologically active structures formed on their basis on the surface of cells and the reaction of the cellular membrane to the adsorbed polymer.     

Adiabatic compressibility of polyelectrolytes in aqueous solutions. II. Poly(4-vinyl-N-n-butylpyridinium bromide)

The adiabatic compressibility for two samples (F-1 with DP-3748 and F-2 with DP-2114) of poly(4-vinyl-N-n-butylpyridinium bromide) in aqueous solution has been determined from ultrasonic velocity and density data. The sample (F-1) with the higher degree of polymerization shows comparatively higher velocity and density in solution. However, the evidence for the difference in compressibility is not very decisive. The apparent molal volume ΦV₂ and apparent molal compressibility ΦK₂ for F-1 are found to be slightly higher than for F-2. In aqueous solution, the decrement of adiabatic compressibility per unit concentration, (β₁ ? β)/c, is found to be almost constant throughout the entire concentration range, whereas in the presence of excess added electrolyte (1.0M KBr solution), the compressibility decrement shows a decrease with dilution. The latter values are lower than those found in water, since the molecules, in the presence of excess electrolyte, are coiled up more and are less compressible. The ΦV₂ and ΦK₂ values in water are constant throughout the entire concentration range, as the free counterions formed on dissociation in the dilute region are not solvated and hence contribute little to the compressibility. On the other hand, in the presence of excess KBr (1.0M), the ΦV₂ and ΦK₂ values show a sharp decrease with increase of polyelectrolyte concentration and finally attain a constant value. This is explained by the fact that because of the formation of a charge-transfer complex between the bromide ion and the polycation, more than the equivalent number of bromide ions is bound, leaving free an equal amount of K⁺ ions which are solvated and cause the lowering of apparent volumes and compressibilities. Condensation of charges begins at a certain polyelectrolyte concentration, and no further increase of K⁺ ions is observed. A special situation arises in 0.1M KBr solution. The ΦV₂ and ΦK₂ values at first increase sharply with increase of polyelectrolyte concentration, but then level off to attain a constant value, at comparatively high concentration. In 2.0% poly(4-vinyl-N-n-butylpyridinium bromide) solution, the concentration of polymer repeat unit (0.08M) is almost equal to the concentration of the added electrolyte (0.1M KBr) used to suppress dissociation. As the polyelectrolyte concentration in 0.1M KBr solution is progressively decreased, more bromide ions are made available for forming the charge-transfer complex with the polycation, leaving the K⁺ ions free to contribute to the compressibility.     

Alternate multi-layered adsorption of macro-cations and -anions on the colloidal spheres. Influence of the deionization of the complexation mixtures with coexistence of the ion-exchange resins

The alternate multiple adsorption layers of macrocations and macroanions on the surfaces of colloidal spheres, in which the complexation mixtures are deionized with ion-exchange resins are studied with help of the electrophoretic light-scattering, dynamic light-scattering and transmitted electron-microscopy techniques. The results are compared with those without resins. Colloidal silica spheres (110 nm in diameter) and monodispersed polystyrene spheres (220 nm) are used as colloidal spheres. The macrocations used are poly (4-vinyl-N-n-butyl pyridinium bromide) and poly (allylamine hydrochloride). Sodium poly (styrene sulfonate) and sodium polyacrylate are used as macroanions. The macroion-colloid complexations are formed firmly when the complexation suspensions are deionized with the resins.     

Dielectric relaxations in a series of vinyl aromatic polymers: Poly(2-vinyl-N-ethylcarbazole), poly(3-vinyl-N-ethylcarbazole), poly(2-vinylanthracene), and poly(α-methyl-2-vinylanthracene)

Two dielectric relaxations have been studied on poly(2-vinyl-N-ethylcarbazole) (P2VK) and poly(3-vinyl-N-ethylcarbazole)(P3VK), poly(2-vinylanthracene) (P2VA) and poly(α-methyl-2-vinylanthracene) (PMe2VA). The relaxations in P2VK and P3VK occur in the temperature regions 220°C and ?150°C. Evidence for a third relaxation in both polymers at ca. 120°C has been found; and, for this reason, the relaxations studied (220°C and ?150°C) are labeled α and β, respectively, and have been attributed to T_g and carbazole rotational libration about the bond connecting the carbazole moiety to the polymer backbone. Additionally β (ca. 20°C) and γ(ca. ?150°C) relaxations in P2VA and MeP2VA have been observed and assigned, respectively, to wagging motion and rotational libration of the pendant anthracene moiety.     

Theoretical prediction of minima in association constants for complex formation between alkylviologens and indole derivatives in the presence of polyelectrolytes

Association constants K for the complexation between various alkylviologens (methyl, propyl, butyl, pentyl, and hexyl) and indole derivatives (acetate and butyrate) have been determined. The order of K values indicates the important role of hydrophobic interactions in aiding the formation of charge transfer complexes. Influences of two kinds of polyelectrolytes; i.e., potassium polystyrenesulfonate (KPSS, anionic) and 3,3-ionene (cationic) on the K values were also examined. KPSS decreased the K value but, interestingly, yielded a minimum, and the K value increased at high KPSS concentrations. The influence of the type of alkylviologen on the K versus [KPSS] plots was successfully understood by a theory of substrate partitioning between bulk water and the environment of the polymer.     

Application of Bender's salts to the synthesis of S-vinyl-O-tert-alkylthiocarbonates

Three thermally labile Bender's salts were synthesized and utilized to effect quantitative S_N2 displacement of primary halides to form tert-alkylthiocarbonate derivatives. Selective displacement of bromide from 1,2-bromochloroethane by either VI or VII followed by dehydrohalogenation with potassium tert-butoxide yielded S-vinyl-O-tert-butylthiocarbonate (I) and S-vinyl-O-tert-amylthiocarbonate (X), two excellent vinyl monomer precursors for polymercaptan, in 62 and 51% yield, respectively. Reaction of VI with vinylbenzyl chloride yielded S-(vinylbenzyl)-O-tert-butylthiocarbonate which polymerized in the presence of free radical initiators to produce a poly(vinylbenzyl mercaptan) precursor. Dilatometric studies of the homopolymerization of I demonstrated that the polymerization rate was proportional to [I]^0.765 and [M]^1.7, respectively; the monomer exhibited a high chain transfer constant (C_M = 3.9 × 10^?3).     

Interaction between poly(N-vinylpyrrolidone) and poly(acrylic acid)s: Influence of hydrogen and cupric ions on the adduct formation

Interpolymer adduct formation between poly(N-vinylpyrrolidone) (PVP) and poly(methacrylic acid) (PMAA) is mainly due to hydrogen bonding. It is found that the interpolymer adduct formation is enhanced in the presence of Cu(II). A simple turbidity measurement making use of a spectrophotofluorometer is described for the study of the interpolymer adduct formation. Enhanced adduct formation in the presence of Cu(II) is described by the empirical relation d[PAd]/D[PVP] = k × 10^4α[Cu(II)]^α, where PAd represents the interpolymer adduct and α and k are constants. Similar results have been obtained in the case of interpolymer adduct formation between poly(acrylic acid) (PAA) and PVP. In the above expression α signifies the influence of chelation on Cu(II)–PAA/PMAA–PVP-type complex formation and k is the extent of PVP–PAA/PMAA interaction. The enhancement of adduct formation in the presence of Cu(II) is more in PAA than in PMAA. Turbidity and viscosity measurements further indicate that the influence of Cu(II) on interpolymer adduct formation between PVP and PMAA or PAA is more in the case of PAA than PMAA, as PAA is a better chelating ligand. But the extent of adduct formation is more in the case of PMAA in the absence of Cu(II) ions due to hydrophobic interactions exerted by methyl groups.     

A FLUORESCENCE STUDY OF THE INTERACTION OF INDOLIC COMPOUNDS WITH SYNTHETIC POLYELECTROLYTES

Abstract— –The interaction of indole derivatives with synthetic polyelectrolytes was investigated using UV absorption and fluorescence spectroscopy. The presence of both sodium poly(styrene sulfonate) (PSS) and sodium polyvinyl sulfonate) (PVS) inhibits the fluorescence quenching of 1-pyrene sulfonic acid by tryptamine. The effect is more marked for PSS than for PVS. There was no polyelectrolyte effect on the quenching by tryptophan. It was also found that aromatic polyelectrolytes strongly quench the fluorescence of indole derivatives of opposite charge by a static mechanism. This is accompanied by a new absorption in the red extreme of the UV spectrum of the mixtures. The systems investigated were tryptamine-PSS and polyvinyl benzyl trimethylammonium chloride) with the anions of indole-3-alkanoic acids. Equilibrium constants for the binding of the indole derivatives to the polyelectrolytes were determined. The fluorescence of zwitterionic tryptophan is not affected by the presence of the polyelectrolytes.     

Study of the thermal degradability of poly(α-methylstyrene) with modified end groups

To induce degradabilities in polymers in response to environmental conditions, endm odification reactions of poly(α-methylstyrene) (PMS) derivatives were carried out. 2-Phenylallyl halide derivatives such as 2-phenylallyl bromide, 2-(p-tolyl)allyl bromide, and α-trifluoromethylstyrene were found to be suitable end-modification agents. For example, the ω-2-phenylallyl-PMS derivative was prepared with almost quantitative functionality by the reaction of the living PMS derivative with 2-phenylallyl bromide. In a similar way, ω-3,3-difluoro-2-phenylallyl- and ω-2-(4-toly)allyl-PMS derivatives were synthesized. Based on thermogravimetric analysis, the onset of the degradation temperature of the endmodified PMS derivatives decreased in the following order: ω-hydrogen- > ω-3,3-difluoro-2-phenylallyl- > ω-2-phenylallyl- > ω-2-(p-tolyl)allyl-PMS. Actually, the onset temperature of ω-2-(p-tolyl)allyl-PMS derivatives was 50°C lower than that of ω-H-PMS derivatives. These results indicate that the active species is produced effectively at the endunsaturated bond, which initiates depolymerization of the polymer at rather low temperatures. Therefore, it is concluded that a 2-phenylallyl substituent at the end of the PMS chain induces effective degradation through a radical mechanism.     

Colloidal single crystals of silica spheres in the presence of simple- and poly-electrolytes,and ionic detergents

Colloidal single crystals of silica spheres (103 nm in diameter) are formed in the presence of various kinds of salts 1 simple electrolytes, i.e., sodium chloride, calcium chloride and lanthanum chloride, 2 polyelectrolytes such as 3–6 type ionen polymer (polybrene), poly-N-ethylpyridinium bromide, a copolymer ofN-benzyl pyridinium chloride andN-hexadecyl pyridinium bromide, and sodium polyethylene sulfonate, and 3 cationic and anionic detergents, hexadecyltrimethylammonium bromide and sodium dodecylsulfate. Shape and size of their single crystals, phase diagram, and the relationship between the two parameters among the critical concentration of melting, conductance and pH of the crystal-like suspensions have been studied. Colloidal single crystals ofpositively charged spheres have been formed in this study by the method of the charge reversal of spheres through the strong adsorption of cationic polyelectrolytes onto the anionic silica spheres.     

Poly(4-vinylpyridine) catalyzed selective methanolysis of methyl and methylene bromides

The effect of poly(4-vinylpyridine) (PVP) on the methanolysis of methyl bromide and methylene bromide was studied at temperatures between 75 °C and 125 °C. PVP acts as an efficient HBr scavenger promoting the formation of dimethyl ether (DME) and dimethoxymethane (DMM) from the corresponding bromomethanes and methanol in moderate yields with high selectivity. No reaction was observed in the absence of PVP under the conditions adopted. The activity of the catalyst remained unchanged even after five cycles showing the efficacy and application of the polymer as an environmentally green reagent as well as catalyst in this methanolysis reaction.     

Synthesis of chiral SalenZn(II) and its coordination with imidazole derivatives and amino acid ester derivatives

A chiral complex, SalenZn(II) (S), was synthesized and characterized. Its coordination with imidazole derivatives and amino acid ester derivatives was studied by UV-vis spectrophotometric titrations and CD spectroscopy. The binding constants decreased in the order K (Im)>K (2-MeIm)>K (2-Et-4-MeIm)>K (N-MeIm) for imidazole derivatives, and K (AlaOMe)>K (PheOMe)>K (ValOMe) for amino acid ester derivatives with the same configuration and K _D >K _L for amino acid esters with different configuration. CD spectra can quantify the strength of SalenZn(II)-ligand interactions, giving results consistent with the magnitudes of the binding constants. Moreover the minimum energy conformations of the adducts were obtained by simulated annealing, and quantum chemical calculations were performed based on those conformations to explain experimental results at the molecular level.     

Synthesis and functionalities of poly(N-vinylalkylamide). V. Control of a lower critical solution temperature of poly(N-vinylalkylamide)

N-vinyl-n-butyramide (NVBA), N-vinylisovaleramide (NVIVA), and N-vinyl-n-valeramide (NVVA), which are N-vinylalkylamides with different alkyl groups were synthesized and their solution behavior in a polymeric form was examined. Copolymers of N-vinylisobutyramide (NVIBA) with N-vinylacetamide (NVA), NVIBA with NVVA, and NVVA with NVA were prepared by the solution polymerization to control the LCSTs. The resultant polyNVBA showed a lower critical solution temperature (LCST) sharply at 32°C, but polyN-vinylisovaleramide (polyNVIVA) and polyN-vinyl-n-valeramide(polyNVVA) that have n-butyl and isobutyl groups, respectively, on their side chains were insoluble even in cold water. The water solubility of the resulting polymers was found to vary, depending on the molecular shapes as well as the side chain length of the alkyl groups in question. The copolymers consisting of NVVA, NVIBA, and NVA in water showed LCSTs sharply between 10 and 90°C, depending on changes in their comonomer content. It was found that the changes in LCST that are caused by the incorporation of comonomers are due to changes in the overall hydrophilicity of the polymer. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3087–3094, 1997