Functional polymers for colloidal applications. VII. Aggregate formation of lipophile-modified polyacrylates in aqueous solutions

Water-soluble copolymers, poly(dodecyl acrylate–coacrylic acid) (PDA), are synthesized by copolymerizing different ratios of dodecyl–acrylate/acrylic acid. Their aqueous solutions are transparent. The plots of I₁/I₃ (the intensity ratio of pyrene emission at 374 nm and 385 nm) and of surface tension as a function of polymer concentrations are combined to verify the existence of the aggregates of PDAs. It is found that the aggregations begin to form at concentrations below that of the polymer transfer to the air–water interface. The plots of I₁/I₃ as a function of polymer concentration shows that the polymers with a higher ratio of dodecyl acrylate form polymer aggregates at lower concentrations. The hydrophobicity of the inner core of polymer aggregates is close to that of sodium dodecyl sulfate (SDS). Polymer solutions of PDA 30, PDA 30L, and PDA 15, show significant solubilization ability to pyrene. (The molar ratio of dodecyl acrylate/total acrylates is 30%, 30%, and 15% for PDA 30, PDA 30L, and PDA 15, respectively. L, low molecular weight.) The solubilization ability increases with the increase in polymer concentration and degree of substitution of dodecylamine. The intensity ratio of the excimer emission to monomer emission of pyrene (I_e/I_m) increases with increasing polymer concentration, roughly parallel to the increase in the amount of pyrene solubilized. However, the I_e/I_m at a fixed pyrene concentration (I_e/I) decreases with increasing polymer concentration. These phenomena are interpreted in terms of the amount of pyrene solubilized and the size and concentration of the polymer aggregates. © 1993 John Wiley & Sons, Inc.     

Living metathesis polymerization of (p-n-butyl-o,o,m,m-tetrafluorophenyl)acetylene by MoOcl4-n-Bu4Sn-EtOH (1:1:1)

Summary Possibility of living metathesis polymerization by Mo catalysts was examined for (p-n-butyl-o,o,m,m-tetrafluorophenyl)acetylene, which has two fluorine atoms at both ortho positions. The MoOCl₄-n-Bu₄Sn-EtOH (1:1:1) catalyst yielded a polymer with narrow molecular weight distribution ( ), but the corresponding MoCl₅-based catalyst did not formed such a polymer. With the former catalyst, the number-average molecular weight of polymer increased in direct proportion to monomer conversion, while the molecular weight distribution remained narrow; this proves the livingness of the polymerization. The optimal conditions for the living polymerization were [n-Bu₄Sn]/[MoOCl₄]=∼1.0, [EtOH]/[MoOCl₄]=0.5–1.5, and temperature≤30 °C. n-Butyl acetate and acetone as well as EtOH were effective as third catalyst components.     

Cocatalytic activities of methylaluminoxane prepared by direct water addition method in ethylene polymerization over Cp2ZrCl2

The characterization of ethylene polymerization behaviors catalyzed over Cp₂ZrCl₂/MAO homogeneous system using methylaluminoxanes prepared by the direct hydrolysis of AlMe₃ (Me=methy1) were reported. The MAO was prepared at the ratio of [H₂O]/[A1]=1 and 0.5 and at three different temperatures, i.e., −40, −60 and −80 °C. The polymerization rate was not decreased with polymerization time when the MAO prepared at the ratio of [H₂O]/[AlMe₃]=l at −60 °C was used as a cocatalyst regardless of the ratio of Al/Zr and the polymerization temperature. The polymerization rate drastically decreased with polymerization time above 60 °C in case of using MAO prepared at the ratio of [H₂O]/[AlMe₃]=l at −80 °C. However, in case of the MAO prepared at the ratio of [H₂O]/ [AlMe₃]=0.5 at −80 °C, the rate continuously increased with polymerization time at the polymerization temperature of 70 °C and 80 °C. The amount of MAO needed to activate Cp₂ZrC1₂ was larger than that of MAO prepared at the ratio of [H₂O]/[A1]=1. The viscosity molecular weight of polyethylene (PE) cocatalyzed with MAO prepared at the ratio of [H₂O]/[Al]=0.5 was lower than that of polyethylene obtained with MAO prepared at the ratio of [H₂O]/[A1]=1.     

Self-association of hyperbranched poly(sulfone-amine) in water: studies with pyrene-fluorescence probe and fluorescence label

Both pyrene-fluorescence probe and fluorescence label techniques are used to investigate the association behaviors of hyperbranched poly(sulfone-amine) (HPSA) in aqueous solution. In the presence of HPSA, excimer emission peak evidently appeared, while no excimer peak was observed in the emission spectra in the absence of HPSA. The excitation spectrum monitored at excimer emission red shifts by about 38-40 nm compared to that monitored at monomer emission, which shows that the excimer is formed by preassociated pyrene chromophores. In the same concentration of pyrene, monomer emission of pyrene decreases but excimer emission increases with increasing the concentration of HPSA; the ratio of excimer-to-monomer emission intensity (I_E/I_M) gradually increases, reaches a critical point at 5-7 g/l, and sharply increases with the concentration. Pyrene-labeled hyperbranched poly(sulfone-amine) (Py-HPSA) was synthesized from 4-(1-Pyrene)butyroyl chloride and HPSA. The monomer emission and excimer emission of Py-HPSA show the concentration-quenching effect, while I_E/I_M increases monotonously, approaches a critical point, and then suddenly increases with increasing the concentration of Py-HPSA. Influences of acidity and solvents on the fluorescence emission were studied. In high concentrations of hyperbranched polymer, pH and DMSO significantly influence the emission of pyrene, and excimer peak disappears at 72% of DMSO fraction.     

Change in the molecular weight distribution of poly(ethylene oxide) caused by the complexation with poly(acrylic acid)

The complexation between poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) was made by using double the molar quantity of either polymer component at pH 2 where the resulting complex completely precipitates. After the removal of the precipitate, PEO or PAA remaining in the supernatant was subjected to gel permeation chromatography to investigate the change in the molecular weight distribution (MWD) caused by the complexation. No remarkable difference is observed in the MWD curves for PEO[1] (M_w=1.37 × 10⁴) before and after the complexation with PAA[1] (M_w=1.10 × 10³) and PAA[2] (M_w=4.16 × 10⁵). However, the MWD curves of PEO[2] (M_w=1.26 × 10⁵) and PAA[2] become shortened and shift to the low molecular weight side after the complexation with PAA[1] or [2] and PEO[2], respectively. This tendency is enhanced by increasing the complexation temperature. From these results, it is indicated that the complexation between PEO and PAA deals with an equilibrium reaction, and the equilibrium constant is dependent on the chain length of both polymer components and also on the complexation temperature.     

Kinetics of ligand exchange reaction of Cu(II)-ammine complex with poly(vinyl alcohol) in aqueous solution

The kinetics of the ligand exchange reaction of the Cu(II)-ammine complex with poly(vinyl alcohol) (PVA) has been studied by a stopped-flow method at pH 9–10, at μ=0.1 (NH₄Cl) and at 25°C. The reaction is initiated by the formation of unstable [Cu(NH₃)₃]²⁺ by the attack of H⁺ on Cu(II)-ammine complex, and proceeds through the mixed complex {[Cu(NH₃)₃(O?PVA)]²⁺}. This step may be rate-determining, followed by a rapid reaction. Finally, the Cu(II) ion is taken up by PVA. The rate is given by d[Cu(II)?PVA]/dt=k[H⁺]{[Cu(NH₃)₄]²⁺}[PVA]/[NH₄Cl], where k=k₁ + k′₂[H⁺], k₁=4.25× 10s^?1 and k′₂=5.20× 10¹¹l mol^?1s^?1.     

Supramolecular assembly of one-dimensional channels and two-dimensional brick-wall networks from asymmetric dithioether ligands and copper(I) iodide

Two asymmetric dithioether ligands with cyclohexyl (L¹) and phenyl (L²) end-groups were synthesized. Reaction of L¹ with copper(I) iodide afforded a 1D channel-type coordination polymer {[Cu₄I₄(L¹)₂](CH₃CN)_0.5}_n (1) interconnected by cubane-type tetranuclear Cu₄I₄ cluster units. Whereas, a 2D brick-wall-type coordination polymer [CuI(L²)]_n (2) with rhomboid dinuclear Cu–I₂–Cu nodes was isolated from the reaction of L² with copper(I) iodide.     

Functional polymers for colloidal applications. IV. Aggregate formation of lipophile-grafted water-soluble copolymers in aqueous solutions

A water-soluble styrene–maleic anydride copolymer (SMA) is derivatized with different lipophilic groups, butylamine and dodecylamine, with different degrees of substitution (5, 15, and 30%). These lipophile-grafted SMAs are water-soluble, and their solutions are transparent. A plot of I₁/I₃ as a function of polymer concentrations indicates the extent of aggregate formation. Surface tension methods also verify the existence of aggregates. It is found that the aggregates begin to form at concentrations below that of the polymer transfer to the air–water interface. The plots of I₁/I₃ as a function of polymer concentrations for SMAs of different molecular weights derivatized with different lipophile with varying degrees of substitution show that the polymers with a higher degree of substitution and lower molecular weights aggregate at lower concentrations. Polymers substituted by butylamine form aggregates at a very high concentration, independent of the degree of sub-stitution. These phenomena are interpreted in terms of hydrophobic interactions as in micelles formed from surfactants. The higher degree of dodecyl-substituted SMA solubilizes pyrene at higher concentrations, and these pyrene solubilized solutions show pyrene excimer emission spectra. These emission spectra are used to characterize the relative size and hydrophobicity of aggregates. © 1993 John Wiley & Sons, Inc.     

Amino‐functional electrospun nanofibrous membrane for detecting nitroaromatic compounds

A novel amino‐functionalized polystyrene copolymer (PS‐NH₂) was designed and synthesized with styrene and 4‐vinylbenzyl amine. Additionally, an amino modified glass (G‐NH₂) was obtained as a carrier. (PS‐NH₂/pyrene)/G‐NH₂ fluorescent nanofibrous membrane [named (PS‐NH₂/pyrene)/G‐NH₂] was designed and prepared via electrospinning technique to detect representative saturated nitroaromatic (NAC) explosive vapor. The (PS‐NH₂/pyrene)/G‐NH₂ showed highly fluorescence stability in ambient condition and further displayed a high quenching efficiency of 70.9% toward trinitrotoluene (TNT) vapor (～10 ppb) with an exposure time of 150 s at room temperature. The abundance of amino groups could effectively adsorb NACs and the binding of electron‐deficient NACs to the amino groups on the (PS‐NH₂/pyrene)/G‐NH₂ surface led to the formation of charge‐transfer complexes. The quenching constant (K_SV) to TNT was obtained to be 1.07 × 10¹¹ mL/g in gaseous phase with a limit of detection up to 2.76 × 10^?13g/mL. Importantly, the (PS‐NH₂/pyrene)/G‐NH₂ showed notable selectivity toward TNT and 2,4‐dinitrotoluene vapors. Straightforwardly, the colorimetric sensing performance can be visualized by naked eye with a color change for detecting of different vapor phase NACs explosives. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46708     

Equation of state for polymer solution

The flow pattern through a cloud of polymer segments is obviously different from the flow pattern around a solid object. It can be shown theoretically, however, that the partial viscosity due to the cloud can take the same value as for a solid sphere with the radius of gyration of the cloud as its radius. The specific viscosity of polymer solution has been derived as 2.5(c/c_I), with c_I being the internal concentration associated with a polymer molecule. The internal concentration is the ratio of mass over the volume of gyration of segments in a polymer chain. A radius of gyration exists for any type of polymers, flexible or rigid, exhibiting different kinds of dependence on the molecular weight. From the expression of the specific viscosity, the intrinsic viscosity is shown to be equal to 2.5/c^∗, c^∗ being the (minimum) internal concentration for the state of maximum conformational entropy. The equation for the specific viscosity, thus obtained, is expanded into a polynomial in c[η]. This formula is shown to agree with data for several kinds of polymers, with flexible, semi-rigid and rigid.The quantity 1/c_I can be interpreted as an expression for the chain stiffness. In polyelectrolytes, coulombic repulsive potentials affect the chain stiffness. The dependence of c_I on the effective population of polyions in the polyelectrolyte molecule is discussed.An equation of state for the polymer solution is formulated that included the internal concentration. The virial coefficients emerge as a result of c_I not always being equal to c^∗, and they are molecular weight dependent.     

Effect of molecular weight on the dissolution properties of polystyrene latex films

An in situ steady-state fluorescence (SSF) technique was applied in order to study the dissolution process of polystyrene (PS) latex films. The effect of the molecular weight M _w of the PS on the dissolution rate was investigated. The PS chains were copolymerized with (1-pyrene)methyl methacrylate in order to make use of pyrene (P) as a fluorescent probe to monitor the dissolution process. Seven different films were prepared from P-labeled PS latex dispersions with different molecular weights at room temperature. These films were then annealed at 200 °C for 15 min to complete the film formation process before dissolution. The dissolution of PS films in a toluene (70 %)–cyclohexane (30 %) mixture was monitored in real time by watching the change in the fluorescence intensity of P, I _P. We used a model that included both case I and case II diffusion kinetics to interpret the results of the dissolution experiments. The relaxation constants k ₀ and the dissolution coefficients D _d of the polymer chains were measured. Two different dissolution coefficients were obtained, which were attributed to the small and long polymer chains in the film, considering the high polydispersity of the polymer. It was also found that both of the D _d values scaled with M _w according to the law D _d ≈ M ^?n .     

Fluorescence and electrochemistry studies of pyrene-functionalized surface adlayers to probe the microenvironment formed by cholesterol

We have synthesized a series of pyrene/cholesterol co-functionalized adlayers on quartz, oxidized silicon, indium-doped tin oxide and gold substrates. The pyrene derivative is N-1-pyrenesulfonyl-ethylenediamine (PSEDA) and the cholesterol derivative is cholesterol-ethylenediamine (Chol-NH₂), which was bound covalently to substrates through epoxide functionalities. X-ray photoelectron spectroscopy shows covalent attachment of both moieties. Optical ellipsometry shows an increase of ca. 5 Å with pyrene/cholesterol co-attachment on oxidized silicon wafers, and an increase of ca. 12 Å when only pyrene was added. Steady-state fluorescence measurements indicate the presence of cholesterol reduces the efficiency of pyrene excimer formation and provides a less polar environment as sensed by the PSEDA I₁/I₃ band ratio. The amount of pyrene excimer formed depends on the reaction time for the adlayer co-deposition reaction. Cyclic voltammetry shows that covalently bound PSEDA is oxidized at ca. 540 mV and physisorbed PSEDA is oxidized at ca. 780 mV. AC voltammetry shows that Chol-NH₂ in the adlayer reduces the electron transfer rate for the PSEDA redox reaction.     

Surface and photoelectrochemical studies of semiconducting MoS2

Redox reactions with Cu(NH₃)^2+/1+_x, Fe(CN)^3?/4? and I^?₃/I₂ were studied on |-C surfaces of MoS₂ using rdes. From electrophoretic measurements, the zpc was found to occur at pH 2. The role of potential-determining ions and the effects of specific adsorption of ions on the electrode behaviour have been discussed. The change of potential with pH was ? 30 mV/pH unit for MoS₂ electrode in contact with a solution saturated with molybdenum and S^2? ions. From the information available, an energy level diagram has been constructed. This diagram is in agreement with the observed behaviour that electron exchange for the first three redox couples occurs with the conduction band, except that the electron transfer from the reduced species, Fe(CN)^4?₆ and Fe²⁺, in the reverse direction (oxidation) is partly and totally restricted, respectively. The charge transfer behaviour in the cse of I^?₃/I₂ couple, appears to be much more complex, most probably involving adsorption of I^? on the surface.     

End-functionalized polymers by living cationic polymerization

Summary End-functionalized poly(isobutyl vinyl ether) (2) with a terminal amine, carboxylic acid, or ester group was prepared by quenching the HI/I₂-initiated living polymer ends with ring-substituted anilines (H₂N-C₆H₄-X, p or m; X = NH₂, COOH, COOC₂H₅). The living polymerization of isobutyl vinyl ether and the subsequent end-capping reaction were carried out at –15°C in methylene chloride. The resulting polymers exhibited a narrow molecular weight distribution and carried one terminal function (aniline residue) per chain, according to ¹H NMR structural analysis.     

Synthesis and cytotoxicity of a ruthenium nitrosyl nitric oxide donor with isonicotinic acid and a cell penetrating peptide

The syntheses and properties of trans-[Ru(NH₃)₄(L)(NO)](BF₄)₃ (L = isonicotinic acid (inaH) (I) or ina-Tat48–60 (II)) are described. Tat48–60, a cell penetrating peptide fragment of the Tat regulatory protein of the HIV virus, was linked to the ruthenium nitrosyl through inaH. I and II release NO after reduction forming trans-[Ru(NH₃)₄(L)(H₂O)]^3 +. The IC₅₀ values against B16-F10 melanoma cells of I and II (21 μmol L^− 1 and 23 μmol L^− 1, respectively) are close to that of the commercially available cisplatin (33 μmol L^− 1) and smaller than similar complexes. The cytotoxicity is assigned to the NO released from I and II.     

The use of 2,6-bis (N-pyrazolyl) pyridine as an efficient dopant in conjugation with poly(ethylene oxide) for nanocrystalline dye-sensitized solar cells

Poly(ethylene oxide) (PEO)/2,6-bis (N-pyrazolyl) pyridine (BNPP) polymer electrolyte based photoelectrochemical cells have been fabricated with [cis-dithiocyanato-N, N-bis (2,2′ bipyridyl-4, 4′ dicarboxylic acid)ruthenium(II)] dihydrate (N3 dye) dye complex as the sensitizer and nanoporous TiO₂ film as photo anode. The introduction of 2,6-bis (N-pyrazolyl) pyridine into the poly (ethylene oxide) matrix reduces the crystallinity of the polymer and enhances the mobility of I⁻/I₃⁻ redox couple resulting in an improved performance with a higher conversion efficiency of 8.8% in terms of light energy to electric energy when compared to that of the corresponding dye-sensitized nanocrystalline TiO₂ solar cell.     

Tris(acrylato)uranylates as a scaffold for NLO materials

Novel uranyl acrylate complexes with general formula R[UO₂(CH₂CHCOO)₃] (RK⁺, NH₄⁺, Rb⁺, or Cs⁺) were synthesized and characterized by X-ray diffraction, IR spectroscopy and second harmonic generation (SHG) measurements. All four compounds are isostructural and crystallize in the non-centrosymmetric P2₁3 space group. Acrylate anions act as bidentate chelating ligands forming [UO₂(CH₂CHCOO)₃]⁻ complexes which are connected through electrostatic interactions with counter ions. SHG measurements revealed the inverted correlation between the Q = I_2ω/I_2ω SiO₂ values and the radii of counter ions.     

[NCO]/[OH] and acryl-polyol concentration dependence of the gelation process and the microstructure analysis of polyurethane resin by dynamic light scattering

The gelation process and the microstructure after the gelation of polyurethane resin consisting of acryl-polyol and polyisocyanate was investigated by dynamic light scattering (DLS) as a function of stoichiometric ratio, [NCO]/[OH], and the concentration of acryl-polyol, C_polyol. The following conclusions were obtained. First, the sol-gel transition was explained by the so-called site-bond percolation theory. Here polyol groups act as site-occupants, and isocyanate groups act as chemical cross-linkers. Second, the scattering inhomogeneities increased rather gradually around the gelation point, which are the characteristics of the gelation process not from monomeric but from oligomer units. Third, at the gelation point, the characteristic decay time of the fast mode, τ_fast, decreased, and the fraction of the collective diffusion mode, A, increased with [NCO]/[OH], which are due to introduction of cross-linking and/or increase of the rigidity of the network. Finally, the ensemble average scattering intensities, 〈I〉_E, the static inhomogeneities, 〈I_C〉_E, the time-average dynamic fluctuating component, 〈I_F〉_T and the collective diffusion coefficient, D, showed remarkable dependence not only on C_polyol but also on [NCO]/[OH]. These are due to the competition between the cross-linking and the progress of micro-phase separation.     

Regeneration mechanism of a Lean NOx Trap (LNT) catalyst in the presence of NO investigated using isotope labelling techniques

The presence of NO during the regeneration period of a Pt–Ba/Al₂O₃ Lean NO_x Trap (LNT) catalyst modifies significantly the evolution of products formed from the reduction of stored nitrates, particularly nitrogen and ammonia. The use of isotope labelling techniques, feeding ¹⁴NO during the storage period and ¹⁵NO during regeneration allows us to propose three different routes for nitrogen formation based on the different masses detected during regeneration, i.e. ¹⁴N₂ (m/e = 28), ¹⁴N¹⁵N (m/e = 29) and ¹⁵N₂ (m/e = 30). It is proposed that the formation of nitrogen via Route 1 involves the reaction between hydrogen and ¹⁴NO_x released from the storage component to form ¹⁴NH₃ mainly. Then, ammonia further reacts with ¹⁴NO_x located downstream to form ¹⁴N₂. In Route 2, it is postulated that the incoming ¹⁵NO reacts with hydrogen to form ¹⁵NH₃ in the reactor zone where the trap has been already regenerated. This isotopically labelled ammonia travels through the catalyst bed until it reaches the regeneration front where it participates in the reduction of stored nitrates (¹⁴NO_x) to form ¹⁴N¹⁵N. The formation of ¹⁵N₂ via Route 3 is believed to occur by the reaction between incoming ¹⁵NO and H₂. The modification of the hydrogen concentration fed during regeneration affects the relative importance of H₂ or ¹⁵NH₃ as reductants and thus the production of ¹⁴N₂ via Route 1 and ¹⁴N¹⁵N via Route 2.     

On the reactivity of the electrogenerated cobalt(I) species towards aryl halides in the presence of allylethers

The electrochemical behavior of CoBr₂ has been investigated in the presence of allylic ethers in an acetonitrile + pyridine (v/v = 9/1) mixture. Cyclic voltametry experiments show a complexation reaction between the electrogenerated cobalt(I) species and allylethers leading thus to a more stable Co^I via the formation of a (η²-allyl-OR)Co^IBr complex. However, this stabilization is too weak to be observed on the time-scale of cyclic voltametry in the absence of pyridine. The thermodynamic constant for the complexation has been determined. It is also shown that only one molecule of allylether is involved in the stabilisation of Co^I. Interestingly, no intra-molecular oxidative addition of allylether to Co^I was observed on the time-scale of a preparative electrolysis unless the reaction was carried out in an undivided cell in the presence of a sacrificial iron rod releasing iron(II) ions. Conversely, an oxidative addition has been evidenced between the electrogenerated Co^I and aryl halides, ArX. The apparent rate constants for this reaction have been determined for various ArX. Importantly, the rate constants depend on the allylether concentration suggesting that the oxidative addition occurs competitively rather than consecutively with respect to complexation. More importantly, preparative-scale electrolyses of aryl halides and allylphenylether in the presence of CoBr₂ as catalyst lead to the coupling product allylaryl, whereas replacement of allylphenylether with allylethylether produces only ArAr along with ArH.