Synthesis and properties of new water-soluble aliphatic hyperbranched poly(amido acids) with high pH-dependent photoluminescence

Water-soluble fluorescent hyperbranched poly(amido acids) (HBPAAs), based on wholly aliphatic structures were prepared through direct self-condensation of N-(3-aminopropyl) diethano succinate amine (APDESA, AB₂ monomer) in the presence of N,N-dicyclohexylcarbodiimide (DCC) as a condensation agent. The resulting HBPAAs were soluble in water, DMF and THF, and the structure of synthesized AB₂ monomer and polymers was confirmed by IR, ¹H, and ¹³C NMR measurements. TEM image indicated that the HBPAAs self-assembled in H₂O to form a spherical micelle with a diameter ranging from 30 to 50 nm. A significant pH-dependent profile of fluorescent intensity in the pH range from 3 to 10 was observed, wherein pH 4 provided a critical jump as the solution pH was increased. Further increasing the pH to 10 decreased the fluorescence because of partial hydrolysis. Strong fluorescence emission was observed at 395 nm in aqueous media and the fluorescence quantum yields are to 23%. These amphiphilic HBPAAs, with excellent water-solubility, void-rich space, multiple functional peripheries and high blue fluorescence, have potential uses as tracing nanocarriers and molecular-level containers.     

Synthesis and micellization of an amphiphilic biodegradable β-cyclodextrin/poly(γ-benzyl L-glutamate) copolymer

β-Cyclodextrin/poly(γ-benzyl L-glutamate) (β-CD-PBLG) copolymers were synthesized by ring-opening polymerization of N-carboxy-γ-benzyl L-glutamate anhydride (BLG-NCA) in N,N-dimethylformamide(DMF) initiated by mono-6-amino-β-cyclodextrin(H₂N-β-CD). The structures of the copolymers were determined by IR, ¹H NMR and GPC. The fluorescence technique was used to determine the critical micelle concentration (CMC) of copolymer micelle solution. The diameter and the distribution of micelles were characterized by dynamic light scattering(DLS) and its shape was observed by transmission electron microscopy(TEM). The results showed that BLG-NCA could be initiated by H₂N-β-CD to produce copolymer. These copolymers showed an amphiphilic nature and could self-assemble into nano-micelles in water. The CMC of copolymer solution and the size of micelle reduced with the increasing of the proportion of hydrophobic parts. TEM images demonstrated the micelles are all spherical. Such copolymers could be expected to find applications in drug delivery systems and other biomedical domains.     

Synthesis of Cleavable Aryl Sulfonate Anionic Surfactants and a Study of their Surface Activity

A series of cleavable aryl sulfonate anionic surfactants were synthesized from cyanuric chloride, aliphatic amine and H-acid mono sodium salt. Their structures were identified by ¹H NMR, Infrared Spectrum (IR) and Elementary Analysis (EA). Their critical micelle concentrations (CMC) in aqueous solutions at 25 °C were determined by a steady-state fluorescence probe method and a surface-tension method. With the increasing length of the carbon chain, the value of their CMCs and surface tensions under CMC (γ _CMC) initially decreased and then reached a minimum (respectively 2.63 × 10⁻⁵ mol L⁻¹ and 28.29 mN m⁻¹) when the carbon number was 10. The CMC and γ _CMC then increased when the carbon number was increased to 12. The results showed that, compared with sodium dodecyl benzene sulfonate (SDBS), such kinds of surfactants have much lower surface adsorption amounts and greater molecular areas on the aqueous surface.

Grafting of amphiphilic polymers containing quaternary ammonium group on SiO2 surface via surface-initiated ATRP

This article reports the fabrication of hybrid silica nanoparticles using surface-initiated atom transfer radical polymerization (SI-ATRP) technique. The surface of silica nanoparticles were densely grafted with 2-(dimethylamino) ethyl methacrylate (DMAEMA) and then quaternized with 1-bromohexane via two methods. FTIR, ¹H NMR, XPS, SEM, TGA, and GPC were used to determine the chemical structure, morphology, and other properties of the products. SEM images of nanocomposites showed spherical shaped morphology with an average diameter of ∼50 nm and they were direct evidences that the hybrid silica nanoparticles had uniform core-shell morphology. Evolution of GPC traces of grafted polyDMAEMA showed that the SI-ATRP could be conducted in a well-controlled manner.     

Synthesis and characterization of comb-shaped poly(amido amine)-g-PEO via Michael addition polymerization

Linear pH-sensitive poly(amido amine)s were synthesized via Michael addition polymerization of N-aminoethyl piperazine (AEPZ) or 4-aminomethyl piperidine (AMPD) with 1,12-dodecylene diacrylamide (DDA). Successive Michael addition reaction of acryl-terminated poly(ethylene oxide) (A-PEO) with the secondary amine of linear poly(DDA-AEPZ) that has one secondary amine in every repeating unit afforded PEO-grafted poly(amido amine). Variation of grafting degree could be obtained conveniently via tuning the feed molar ratio of acryl/secondary amine. When this ratio equals to 1.2, all the secondary amines on the backbone of poly(DDA-AEPZ) (or poly(DDA-AMPD)) were consumed and the comb-shaped polymers were formed. The amphiphilic comb-shaped poly(DDA-AEPZ)-g-PEO was molecularly dissolved in water at pH 2.0 (w/v=0.25%), and micelles were formed when pH value of aqueous solution was adjusted to 6.5. ¹H NMR data verify the formation of micelles due to the disappearance of signals attributed to poly(DDA-AEPZ). The formation of micelles can be confirmed further by TEM photos, they show that all the particles are approximately spherical and their number-average diameter is around 95 nm.     

Kinetics of hydrogen peroxide oxidation of alkyl dimethyl amines

We measured the absolute rate constants for the hydrogen peroxide oxidation of two different octyl dimethyl amines in isopropanol/water mixtures at 23°C. The amines were 1-octyl dimethyl amine (1) and 2-ethylhexyl dimethyl amine (2); their structures were analogous to those most often encountered in commercial alkyl dimethyl amine oxide production. The observed first-order rate constants for the disappearance of amine across a range of H₂O₂ concentrations (0.5–8 M) indicated that the overall rate was first-order in amine and 3/2-order in H₂O₂. Calculations showed k ₁=0.16 M⁻¹h⁻¹, k ₂=0.046 M⁻¹h⁻¹, and k ₁/k ₂=3.5. The rates appeared to decrease with increasing steric hindrance around the nitrogen atom. We also investigated the effect of water on the reaction rates. When [H₂O]<∼4.5 M in isopropanol, the rates increased with increasing [H₂O]; for [H₂O]>∼4.5 M, the rates were insensitive to [H₂O].     

Temperature and pH-sensitive chitosan hydrogels: DSC,rheological and swelling evidence of a volume phase transition

On heating, alkali chitin solutions undergo phase separation describing a characteristic “U-shaped” cloud point curve with a lower critical solution temperature (LCST) centered at ∼30 °C. The process is accompanied by gelation of the polymer-rich phase. A different strategy to induce alkali chitin phase separation/gelation is by applying vacuum to the solution at room temperature during aprox. 72 h. Once washed to neutrality, chitin gels had a degree of acetylation of ∼30–40% (i.e. they were converted into chitosan). On cooling, these gels exhibit an exothermic peak in micro-DSC and a depression in G^′′ and tan δ traces, evidencing a volume phase transition centered at ∼20 °C. This transition is observed only within a narrow range of pH ∼7.3–7.6. Variation in the mechanical response as a result of cyclic stepwise changes in temperature between 50 and 0 °C at pH values from 7.3–7.6, revealed that the G’ modulus of the gels increases on heating and decreases on cooling, a behavior that persists over at least four cycles of temperature change. Only marginal changes in G’ at pH 8.0 and not at all at pH 12.0 are observed. By contrast, the variation of G^′′ persists throughout the range of pH. This behavior is rationalized in terms of the existence of a fine balance between hydrophobic and hydrophilic interactions at varying temperature and pH, thus effectively controlling swelling and shrinking states of the gel network. The degree of swelling at pH 7.6 reaches a minimum at ∼22–25 °C.     

Synthesis and Properties of Novel Alkyl Sulfonate Gemini Surfactants

A series of novel dialkyl disulfonate gemini surfactants (2C_n-SCT where n is the carbon number of the hydrophobic chain) were synthesized from cyanuric chloride, aliphatic amine and taurine. The chemical structures of the prepared compounds were confirmed by ¹H NMR, ¹³C NMR, IR spectra, and ESI–MS. Their critical micelle concentrations (CMC) in the aqueous solutions at 25 °C were determined by surface tension and electrical conductivity methods. With the increasing length of the carbon chain, the values of their CMC initially decreased, and then increased with an alkyl chain length of 14. The surface tension measurements of 2C_n-SCT (except for n = 14) determined that there is a low CMC, a great efficiency in lowering the surface tension, and a strong adsorption at the air–water interface. In addition, adsorption and micellization behavior of 2C_n-SCT were estimated from pC ₂₀, the minimum average area per surfactant molecule (A _min), and standard free energy micellization and adsorption ( \Updelta G_\textmic^°  \textand \Updelta G_\textads^° \Updelta G_{\text{mic}}^{^\circ } \,{\text{and}}\,\Updelta G_{\text{ads}}^{^\circ } ). These properties are significantly influenced by the chain length n, and the adsorption is promoted more than the micellization.     

In-situ preparation of macroporous network of silicalite-1 nanocrystallites

Large macroporous networks of silicalite-1 nanocrystallites have been produced from the in-situ hydrolysis of tetraethoxysilane (TEOS) in the presence of concentrated solutions of both molecular (tetrapropylammonium) and polymeric (monodispersed polystyrene beads, ∼400 nm) templating agents followed by hydrothermal and calcination treatments. The morphology of these solids has been characterized using SEM, HREM, XRD, ²⁹Si MAS-NMR, nitrogen adsorption–desorption and mercury intrusion techniques. It consists in a somewhat regular array of nanocrystals (∼100 nm) of silicalite-1 (pore size is ca. 6 nm) organized around interconnected macropores of narrow size distribution (330 ± 30 nm). As silicalite-1 crystals are grown into macropores’ walls, a secondary network of mesoscopic voids is formed between the crystallites (25 ± 15 nm). Two out of these three levels of porosity are narrow distributed.     

Spectroscopic and conformational study of chitosan acid salts

The efficient procedure for preparation of chitosan acid salts in isopropyl alcohol under mild condition has been demonstrated. The salts were prepared by dissolving chitosan into ascorbic acid, p-amino benzoic acid and p-nitro benzoic acid, respectively, and then washed with an isopropyl/water mix-solvent. The prepared crystal salt and molecular conformation of modified chitosan derivatives are characterized by using ultraviolet, Fourier transform infrared (FTIR), ¹H nuclear magnetic resonance (NMR), X-ray diffraction and Circular dichroism (CD) techniques. The formation of salts was confirmed by FTIR (∼1,523–1,557 cm⁻¹) and NMR (∼7–8 ppm) with respect to the bonding between NH₂ group on chitosan and COOH group on acid. The CD spectra of chitosan salts showed negative at (253, 285 and 295 nm band) in chitosan ascorbic acid, p-amino benzoic acid and p-nitro benzoic acid salt respectively in DMSO, indicating that the polymer adopted a helical secondary structure. The polymers are highly soluble in a wide pH range, which opens new perspectives for the biomedical application of chitosan based-materials.     

The essential oil fromTagetes minuta L. modulates the binding of [3H]flunitrazepam to crude membranes from chick brain

The hypothesis that the essential oil fromTagetes minuta L. can interact with biological membranes was investigated by assessing its ability of perturbing the binding of a benzodiazepine [flunitrazepam (FNTZ)] to crude membranes from chick brains. The essential oil fromT. minuta L. inhibited [³H]FNTZ specific binding to chick brain membranes. These values were obtained from the analysis of the saturation curve for the kinetic parameters: dissociation equilibrium constant (K_d)=2.47±0.32 nM, maximal binding (B_max)=556±5 fmoles/mg protein, and Hill coefficient (n)=1.00±0.07 in the absence, and K_d=6.73±1.4 nM, B_max=583±69 fmoles/mg protein, and n=1.02±0.08 in the presence of 29 μg/mL of essential oil. The essential oil could self-aggregate with a critical micellar concentration (CMC) of 60 μg/mL. The marked increase in [³H]FNTZ nonspecific binding starting at 60 μg of essence per mL was due to that phenomenon and revealed the ability of self-aggregated structures to interact with membranes. [³H]FNTZ specific binding decrement as a function of essence concentration cannot be ascribed merely to oil's micelles ability of trapping the lipophilic radioligand molecules, because the discontinuous behavior that characterizes a monomer-aggregate phase transition was not shown. Oil's components might behave as competitive inhibitors or allosteric modulators of FNTZ specific binding. However, their ability to increase FNTZ nonspecific binding at concentrations below oil's CMC suggests that this effect may be due to oil's partitioning into the lipid bilayer. This latter phenomenon would induce an increment in membrane fluidity and a change on FNTZ binding site toward a lower affinity conformation. Therefore, the essential oil components can interact with brain membranes either as monomers, by partitioning into the lipid bilayer, or as self-aggregated structures, through an adsorption to the membrane surface.     

Preparation of phenolic resin derived 3-D ordered macroporous carbon

Three-dimensionally ordered long-range macroporous carbon structures were prepared using commercially available phenolic resin by utilizing sacrificial colloidal silica crystalline arrays as templates that were subsequently removed by HF etching after pyrolysis in an argon atmosphere. SEM, TEM, and BET were employed to characterize the morphology and the surface area of the porous carbon structures. The pore size (150–1000 nm) and BET surface area, which reflect pore volume (298.6 m²/g (1.32 cm³/g) ∼ 93.7 m²/g (0.12 cm³/g)), of the macroporous carbon structures produced were approximately proportional to the size (150–1000 nm) of the sacrificial silica sphere templates used (annealing temp. 550°C). The achieved 550 nm porous carbon structures were examined to function as potential catalyst carriers and were successfully impregnated with Ag or Pt-Ru on their inner walls after borohydride reduction at room temperature. In addition, porous carbon patterns were fabricated using the ‘micromolding in capillary’ technique, which has potential applications in the microreaction technology.     

Synthesis and Characterization of Sodium Nonylphenol Ethoxylate(10) Sulfoitaconate Esters

Two sodium nonylphenol ethoxylate(10) sulfoitaconate ester surfactants, namely disodium nonylphenol ethoxylate(10) sulfoitaconate monoester (DNE(10)SIM) and sodium nonylphenol ethoxylate(10) sulfoitaconate diester (SNE(10)SID), were synthesized through the esterification and sulfonation reactions with nonylphenol ethoxylate(10) ester, itaconic acid and sodium sulfite as the raw materials. The chemical structures of the prepared surfactants were confirmed by FTIR and ¹H NMR. The surface tension of the synthesized surfactants was measured at 25 °C and the surface active properties were characterized. The DNE(10)SIM had better surface activity. The CMC was 1.77 × 10⁻⁶ mol L⁻¹ and γ_CMC was 35.45 mN m⁻¹. The CMC and γ_CMC for the SNE(10)SID were 5.42 × 10⁻⁵ mol L⁻¹ and 37.67 mN m⁻¹, respectively. Moreover, the emulsification power of SNE(10)SID was better.     

Solution properties of polymacromonomers consisting of polystyrene

Summary Dynamic light scattering measurements have been made on 14 samples of a polymacromonomer consisting of polystyrene with 15 styrene side-chain units in cyclohexane at 34.5°C (the theta point) to determine the translational diffusion coefficient D as a function of molecular weight. The dependence of D on the main-chain length is analyzed on the basis of the wormlike chain by taking into account the end effect arising from side chains near the main-chain ends. The model parameters describing this dependence, i.e., the Kuhn segment length (11.5 ± 1.5 nm), the linear mass density (5600 ± 700 nm⁻¹), the diameter (5.2 ± 0.5 nm), and the end-effect parameter δ (2.5 ± 0.3 nm), are close to those determined previously from <S ²>_z (the z-average mean-square radius of gyration) and [η] (the intrinsic viscosity), leading to the conclusion that the wormlike chain model is capable of consistently explaining <S ²>_z, [η], and D of the polymacromonomer in the Θ solvent. Received: 8 February 2000/Accepted: 18 February 2000     

Synthesis, Characterization and Performance of Unsaturated Long-Chain Carboxybetaine and Hydroxy Sulfobetaine

The unsaturated long-chain carboxybetaine and hydroxy sulfobetaine were synthesized by the reaction of unsaturated octadecyl tertiary amine with sodium chloroacetate and 3-chloro-2-hydroxypropanesulfonic acid sodium salt, respectively. The structures of the two betaines were characterized by IR and ¹H-NMR spectroscopy. The Krafft points of the two betaines are below 0 °C and the isoelectric points are at pH 8.2 and 8.0, respectively. The surface tensions (γ _CMC) at the critical micelle concentrations (CMC) were measured to investigate the surface activities of the prepared compounds when the pH is equal to 4.0, 6.5 and 10.0 at 50 °C, respectively. Meanwhile, the corresponding saturated betaines were synthesized and determined for comparison. The double bond in the non-polar tail leads to a slightly higher CMC and a lower γ _CMC. Though the CMC of the unsaturated betaine is slightly higher than that of saturated betaine for the double bond in the non-polar tail, the applied range of the unsaturated betaine is broader than corresponding saturated betaine for low Krafft point. The CMC and Г_CMC of the four betaines increase, but the pC₂₀ decreases, with increasing pH. As a whole, the impact of pH on the performance of the four betaines is not very obvious.     

A Novel Zwitterionic Imidazolium-Based Ionic Liquid Surfactant: 1-Carboxymethyl-3-Dodecylimidazolium Inner Salt

A novel zwitterionic imidazolium-based ionic liquid (IL) surfactant, 1-carboxymethyl-3-dodecylimidazolium inner salt, was synthesized. The molecule structure was confirmed by means of electrospray ionization mass spectrometry, ¹H nuclear magnetic resonance and elemental analysis. The isoelectric point (pI) is 3.8 ± 0.1 at 35 ± 0.1 °C. The other important physicochemical parameters such as the critical micelle concentration (CMC), the surface tension at CMC (γ_CMC), the adsorption efficiency (pC ₂₀), the surface pressure at CMC (Π_CMC), the maximum surface excess (Γ_m), the minimum molecular cross-sectional area (A _min), the value of CMC/C ₂₀ and the average number of aggregation (N _m) were determined by surface tension and steady-state fluorescence probe methods, respectively.     

Synthesis and Self-Assembly Behavior of Comb-Like Surfactant Polymethyl Methacrylate-g-Methoxy Polyethylene Glycol

Comb-like surfactant of polymethyl methacrylate-g-methoxy polyethylene glycol (PMMA-g-MPEG) with well-defined structure was synthesized and characterized by FT-IR, ¹H NMR and gel permeation chromatography. Its surface activity and aggregation behavior in aqueous solution were investigated by surface tension measurement, dye encapsulation experiment, transmission electron microscopy (TEM) and dynamic light scattering (DLS). The CMC and surface tension at the CMC of PMMA-g-MPEG were 0.2 g/L and 47 mN/m, respectively. DLS and TEM analysis revealed that PMMA-g-MPEG could self-assemble into spherical micelles with the average hydrodynamic diameters in the range from 20 to 300 nm in aqueous solution.     

Synthesis,characterization and micellization of heterograft copolymers based on phosphoester functionalized macromonomers via “grafting through” method

Novel amphiphilic heterograft copolymers consisting of phosphoester functionalized PEG (phosPEG) and PCL (phosPCL) were synthesized by the ring‐opening polymerization via “grafting through” method. The heterograft structure and thermal properties of these copolymers with various compositions were characterized by ¹H‐NMR, ³¹P NMR, size exclusion chromatography (SEC), and differential scanning calorimetry (DSC) in detail. These amphiphilic copolymers could self‐assemble into micellar structures in aqueous solution, and their critical micellization concentrations (CMC) were determined to be 0.69–1.25 mg/L by fluorescence technique. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements show that these heterograft copolymer micelles are spherical in shape with the particle size ranging from 20 to 60 nm, which has potential in biomedical application. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Liquid products of the alkaline activation of brown coal from the Aleksandriiskoe deposit

The liquid products of the alkaline activation of brown coal from the Aleksandriiskoe deposit (800°C; 1 h; activator, KOH) were studied by thermal analysis, IR spectroscopy, and ¹H and ¹³C NMR spectroscopy. They were formed in ∼30% yield; they consisted of pyrogenic water (∼50%) and a resinous mixture of organic substances with increased hydrogen and oxygen contents and decreased carbon and sulfur contents. On heating, potassium hydroxide completely decomposed the quinoid structures of coal, decreased the concentration of aromatic components in resin, and increased the concentrations of CH₃-, -CH₂-, and OH-groups. This is consistent with the well-known thermally initiated reactions of alkaline degradation and dehydrogenation at high temperatures (400–800°C). The thermal lability of resinous products was evaluated, and the heats of combustion (32.4–32.7 MJ/kg) were determined; the latter values indicate that these products can be used as fuel.     

Oxidation of a coal particle in flow of a supercritical aqueous fluid

A study was made of the conversion of single spherical coal particles of diameter 1–5 mm in a supercritical H₂O/O₂ fluid with an oxygen mass fraction of 0–6.6% in a semibatch reactor at a pressure of 30 MPa and a temperature of 673–1023 K. A decrease in the particle mass was observed in two parallel processes: gasification of coal with water and oxidation of coal with oxygen. An activation energy 19 ± 7 kJ/mole and a pre-exponential factor 10^−2±0.4 sec⁻¹ were obtained under the assumption of zero order for the concentration H₂O and an Arrhenius dependence for the rate of gasification with water. The oxidation with oxygen at a temperature above 780 K was found to be limited by the rate of O₂ diffusion to the coal organic matter. Below 780 K, the rate of heterogeneous oxidation with oxygen is described by a first-order reaction for the concentration of O₂ and a zero-order reaction for the concentration of H₂O with an activation energy of 150 ± 27 kJ/mole and a pre-exponential factor of 10^7.6±1.9 cm³/(g · sec). __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 23–31, March–April, 2008.