Effect of functional group polarity on the encapsulation of C60 derivatives in the inner space of carbon nanohorns

Encapsulation of C₆₀, its hydroxides (C₆₀(OH)_n, n = 10, 36, 44), and its hydride (C₆₀H₃₆) into inner space of carbon nanohorns (CNHs) from solutions or dispersions in various solvents by the nano-condensation method was attempted. The effect of the functional groups on the encapsulation was evaluated by transmission electron microscopy. C₆₀, C₆₀(OH)₁₀, and C₆₀H₃₆ can be efficiently encapsulated inside CNHs using toluene, THF, and DMSO as solvents, whereas C₆₀(OH)₃₆ and C₆₀(OH)₄₄ are hardly encapsulated from any solution. Because the molecular size of C₆₀(OH)₁₀ is similar to that of C₆₀(OH)₃₆ and C₆₀(OH)₄₄, the difference in encapsulation is not caused by molecular size. The efficient encapsulation of C₆₀H₃₆ in CNHs suggests that molecules can be encapsulated in carbon nanomaterials even when the π–π interaction with the sp²-hybridized carbon walls is weak. These results suggest the polarity of the functional group of the C₆₀ derivatives as the main factor in determining whether they can be encapsulated in CNHs. C₆₀(OH)₃₆ and C₆₀(OH)₄₄ contain many hydroxyl groups, thus these molecules self-aggregate and do not pass the holes of CNHs, resulting in poor encapsulation.     

Nafion functionalized carbon nanohorns as catalyst support for proton exchange membrane fuel cells

Carbon nanohorns (CNHs) are synthesized by DC arc-discharge method in helium atmosphere. The synthesized CNHs are heat treated and then functionalized with Nafion. Platinum is reduced onto Nafion functionalized CNHs through ethylene glycol reduction method. Pt/Nafion-CNHs catalysts are prepared by varying deposition times from 1 to 7 h. Detailed characterization of CNHs and the catalyst is performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). Membrane electrode assemblies are prepared by decal method and electrode performance is analyzed using hydrogen pumping technique. SEM and TGA analysis of soot indicates relatively high level purity of CNHs. TEM and XRD analysis of catalyst with 6 h deposition time reveals that Pt nanoparticles are uniformly deposited on multiwall CNHs surface with particle size of 3–4 nm. Hydrogen pumping studies reveals that Nafion functionalized CNHs act as good catalyst support without hindering electron transfer at electrodes. Hence, these graphitic carbon supports have potential application for high power density applications.     

Grafting of poly(ethylene oxide) onto C60 fullerene using macroazo initiators

In order to improve the solubility of C₆₀ fullerene in conventional solvents, grafting of hydrophilic poly(ethylene oxide) (PEO) by utilizing the radical-trapping nature of C₆₀ fullerene was investigated. Macroazo initiators containing a poly(ethylene oxide) unit, known as Azo-PEO, were prepared at various molecular weights by the reaction of 4,4′-azobis(4-cyanopentanoyl chloride) with poly(ethylene glycol) methyl ether. PEO radicals formed by thermal decomposition of Azo-PEO were successfully trapped by C₆₀ fullerene to give PEO-grafted C₆₀ fullerene. Their structures were confirmed by FT-IR spectroscopy, size exclusion chromatography, UV-vis spectroscopy, and differential scanning calorimetry. When Azo-PEO with low-molecular weight was reacted with C₆₀ fullerene, a bis-adduct, C₆₀-(PEO)₂, and a tetrakis-adduct, C₆₀-(PEO)₄, were formed. In contrast, in reactions with Azo-PEO of higher molecular weight, only the bis-adduct was formed, and no formation of the tetrakis-adduct was observed. The structure of bis-adduct was found to be 1,4-type. The solubility of C₆₀ fullerene in water, THF, methanol, and other conventional organic solvents was remarkably improved by grafting of PEO. In addition, the thermal stability of PEO was dramatically increased by grafting onto C₆₀ fullerene.     

Synthesis and radical polymerization of end-allenoxy polyoxyethylene macromonomer

Poly(ethylene glycol) allenyl methyl ether (2) was prepared by the reaction of poly(ethylene glycol) monomethyl ether (the number average molecular weight (M_{n) = 550}) with propargyl bromide, followed by the base-catalyzed isomerization reaction. Functionality of end-allenyl groups in the obtained macromonomer was determined as 92% (from ¹H-NMR). The radical polymerization of 2 was carried out in bulk and in benzene at 60 or 120°C to yield a polymer with poly(ethylene glycol) side chains. For instance, a polymer (3, M_n = 3900) was obtained in 39% yield by the polymerization of 2 in bulk at 60°C for 48 h using 6 mol% of α,α′-azobisisobutyronitrile (AIBN). The obtained polymer was soluble in organic solvents as well as water.     

Effect of polystyrene stars with fullerene C60 cores on pervaporation properties of poly(phenylene oxide) membrane

Star‐shaped macromolecules with six arms of polystyrene grafted onto a fullerene C₆₀ core, or fullerene‐containing polystyrene (FPS), were used for the modification of poly(phenylene oxide) (PPO) and the preparation of a dense thin‐film membrane. The membrane structure was studied using scanning electron microscopy. The effect of FPS modifier on membrane density and mass transfer of methanol and ethylene glycol through the membrane was studied. Sorption and pervaporation tests were used to determine degree of sorption, diffusion coefficients, flux through the membrane and separation factor. In the pervaporation of a methanol–ethylene glycol mixture over the concentration range of 10–30 wt% methanol in the feed, all membranes showed high affinity to methanol. The separation factor reached a maximum at 5 wt% FPS in the membrane. The PPO/FPS membranes exhibit the best separation properties when the feed is enriched with ethylene glycol. © 2016 Society of Chemical Industry     

Competitive mechanism of poly(ethylene glycol) with poly(vinyl methyl ether) in complexing water molecules revealed with elastic light scattering spectroscopy

By using elastic light scattering (ELS) spectroscopy, dependences of lower critical solution temperature (LCST) of poly(vinyl methyl ether) (PVME)/poly(ethylene glycol) (PEG) solutions on concentration (C _PEG) and molecular weight of PEG were analyzed. It was found that the onset temperature of phase separation (T _p) decreased with increasing C _PEG or molecular weight of PEG in the solutions. It indicated that PEG was competitive with PVME in complexing water molecules. The presence of PEG disturbed the hydration layer around PVME, facilitating the aggregation of PVME chains at lower temperature. Moreover, the ELS spectra revealed the aggregation and dissociation of molecular chains in PVME/PEG solutions during one heating and cooling cycle. PVME chains aggregated above the microphase transition temperature. With further increasing temperature, PVME aggregates started to contract, and then kept stable. During cooling, the chain aggregates were not immediately swelled but gradually swelled, and began to dissociate when the solution temperature was further decreased. Finally, the conformation of the molecular chains returned to its original state.     

Newer Non-ionic A2B2-Type Enzyme-Responsive Amphiphiles for Drug Delivery

A new series of nonionic gemini amphiphiles have been synthesized in a multi-step chemoenzymatic approach by using a novel A₂B₂-type central core consisting of conjugating glycerol and propargyl bromide on 5-hydroxy isophthalic acid. A pair of hydrophilic monomethoxy poly(ethylene glycol) (mPEG) and hydrophobic linear alkyl chains (C₁₂/C₁₅) were then added to the core to obtain amphiphilic architectures. The aggregation tendency in aqueous media was studied by dynamic light scattering, fluorescence spectroscopy and cryogenic transmission electron microscopy. The nanotransport potential of the amphiphiles was studied for model hydrophobic guests, that is, the dye Nile Red and the drug Nimodipine by using UV/Vis and fluorescence spectroscopy. Evaluation of the viability of amphiphile-treated A549 cells showed them to be well tolerated up to the concentrations studied. Being ester based, these amphiphiles exhibit stimuli-responsive sensitivity towards esterases, and a rupture of amphiphilic architecture was observed in the presence of immobilized Candida antarctica lipase (Novozym 435), thus facilitating release of the encapsulated guest from the aggregate.     

Synthesis of amphiphilic (meth)acrylates with oligo(ethylene glycol) and (or) oligo(propylene glycol) blocks by the esterification of (meth)acrylic acid

Thermoresponsive PEG-based (PEG stands polyethylene glycol) polymers are unique for use in medicine because of their low toxicity, good biocompatibility and biodegradability, but usually more hydrophobic and more toxic comonomers are used to adjust lower critical solution temperature (LCST). A convenient way to overcome this problem and to finely tune LCST is to use alkoxy oligo(ethylene glycol)- or alkoxy oligo(propylene glycol) (meth)acrylates as starting comonomers. Here we report on the conditions for the simple and affordable synthesis of methoxy oligo(propylene glycol) (meth)acrylate- and methoxy oligo(propylene glycol)-block-oligo(ethylene glycol) (meth)acrylate-based macromonomers with high yields (80%–98.7%) by the acid-catalyzed esterification of (meth)acrylic acid with alkoxy oligo(alkylene glycols) containing oligo(ethylene glycol) (OEG) and/or oligo(propylene glycol) (OPG) blocks. p-Toluene sulphonic acid (pTSA), alkyl(C₁₂–C₁₄)benzene sulfonic acid (ABSA) and H₂SO₄ were used as catalysts. It has been shown that pTSA and ABSA are practically the same in catalytic activity and are superior to sulfuric acid. The reaction orders with respect to catalyst was found to be close to 1 in all cases. It has been shown that the reaction is actually insensitive to the lengths of OEG and OPG blocks, as well as to the structure of the terminal alkyl group, while the esterification of acrylic acid (AA) proceeds much faster compared to methacrylic acid (MAA) one under the same conditions. The influence of temperature on the equilibrium conversions of alcohols was determined, which were found to be 89%–93% for the esterification of AA and 61%–86% for MAA in the temperature range of 60–120°C. A further increase in conversion was achieved by introducing an azeotropic agent (toluene), its optimal concentration was found to be 10%–15%.     

Diamond film deposition from ethylene glycol/water solution using a dc-plasma jet method

A diamond film was deposited from a mixture of ethylene glycol and water using a dc−plasma jet method above liquid, in which the plasma was directly generated on a solution surface. Vaporized molecules from the surface were decomposed into radicals in the plasma. Optical emission spectroscopy revealed the presence of CO, OH, CH, C₂ and H. The relative intensities of C₂ to OH and CH increased with the ethylene glycol content. Diamond was deposited in the concentration range of ethylene glycol from 60 to 90 mol%. The 80 mol% concentration was the optimum value for diamond film deposition, whereas the lower concentration than 80 mol% resulted in an uncovered substrate at the center exposed to the jet. The typical growth rate of the diamond film was 10 μm/h. The crystalline film consisted of well faced particles less than 5 μm in size.     

Interactions between fullerene(C60) and poly(ethylene oxide) in their complexes as revealed by high-resolution solid-state C NMR spectroscopy

A series of poly(ethylene oxide) (PEO)/fullerene(C₆₀) complexes are prepared by lyophilization. The intermolecular interaction and molecular motion in the complex are investigated by solid-state ¹³C NMR spectroscopy. An intense C₆₀ signal due to the intermolecular cross-polarization is observed in the ¹³C CP/MAS spectra of the complex samples, indicating a high degree of dispersion of C₆₀s in the complexes. By measuring the ¹³C spin-lattice relaxation times and ¹H transverse relaxation times of the complex sample and by comparing the static ¹³C spectrum of the pure C₆₀ sample with that of the complex sample, it is demonstrated that there exist n-π interactions between the n-orbitals of the PEO ether oxygen and the π-system of C₆₀. The C₆₀ molecules act as physical cross-links in the amorphous region of PEO, which greatly inhibit the mobility of the surrounding PEO chains, while the rapid isotropic rotation of C₆₀ molecules is also reduced to some extent due to the interactions with the polymer chains.     

Poly(amide-acetals) and poly(ester-acetals) from polyol acetals of methyl 9(10)-formylstearate: Preparation and physical characterization

Condensation polymers were prepared from the pentaerythritol acetal of methyl 9(10)-formylstearate by reaction with diamines and with ethylene glycol. The glycerol acetal was self-condensed to a poly(ester-acetal) and also copolymerized with caprolactam. A novel step growth, addition polymerization was carried out with ethylene bis[9(10)-methoxymethylenesterate] and pentaerythritol. Physical and spectral (infrared and nuclear magnetic resonance) properties of the various products were determined. In general, the long C₈–C₉ side chains in the polymers of the pentaerythritol acetal of methyl 9(10)-formylstearate reduced crystallinity to such a degree that, unlike polymers from methyl azelaaldehydate pentaerythritol acetal, they were soluble in the more ordinary solvents, e.g., chloroform and tetrahydrofuran. Presented in part at the 45th Fall AOCS Meeting, Atlantic City, New Jersey, October 3–6, 1971.     

Reaction of ethylene oxide or propylene oxide with long-chain fatty acids. Mono- and diester formation

Summary The alkali-catalyzed reaction of ethylene oxide or propylene oxide with fatty acids was shown to be complex. Mono- and diesters were formed in comparable amounts even at an early stage when only about one equivalent of the cyclic ether had been condensed. The following compounds were isolated in a pure state: ethylene glycol monolaurate, ethylene glycol dilaurate, diethylene glycol dilaurate, ethylene glycol distearate, 1,2-propylene glycol dilaurate, and 1,2-propylene glycol distearate. A monoester from propylene oxide was shown to be a mixture of the 1-and 2-monolaurate [C₁₁H₂₃CO₂CH₂CHOHCH₃ and C₁₁H₂₃CO₂CH(CH₃)CH₂OH]. Presented at the Delaware Valley Regional Meeting, American Chemical Society, Philadelphia, February 5, 1958. Eastern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

A novel catalyst for the glycolysis of poly(ethylene terephthalate)

Poly(ethylene terephthalate) waste materials were depolymerized by ethylene glycol (EG), diethylene glycol (DEG), and propylene glycol (PG) in the presence of a novel catalytic system: titanium (IV)‐phosphate. The new catalyst was synthesized through a reaction of TiCl₄ with triethyl phosphate (C₂H₅O)₃P(O). It was found that the depolymerization of poly(ethylene terephthalate) fiber proceeds faster in the presence of titanium (IV)‐phosphate compared with compounds traditionally used in this process like Zn(OOCCH₃)₂. The oligomer distribution in the glycolysis products was studied by size‐exclusion chromatography. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1148–1152, 2003     

New Octopus-like Phthalocyanines as Fullerene Receptors: Synthesis and Photophysical Investigation

Octopus-like zinc and magnesium phthalocyaninates bearing eight flexible benzylated diethylene glycol chains were synthesized and their interaction with fullerenes C₆₀ and C₇₀ was investigated by UV-Vis spectrophotometric titration, as well as by steady-state and time-resolved fluorescence spectroscopy in chloroform and toluene media. These measurements revealed a high affinity of receptors for C₆₀ and C₇₀, with selectivity to C₇₀: binding constants for C₇₀ are almost two times higher than for C₆₀. These results are interpreted by means of quantum-chemical calculations using the PM6-DH2 Hamiltonian. The binding constants also depend on both the nature of the metal ion in the receptor and the solvent. It is expected that the obtained molecules and supramolecular complexes can be used for further elaboration of optoelectronic donor-acceptor materials.     

Surface-initiated catalytic ethylene polymerization within nano-channels of ordered mesoporous silicas for synthesis of hybrid silica composites containing covalently tethered polyethylene

A surface-initiated catalytic ethylene polymerization technique is successfully demonstrated herein for the covalent surface-grafting of polyethylene chains within nanochannels of mesoporous silicas to give hybrid mesoporous silica/polyethylene composite materials. In this technique, a Pd−diimine catalyst, [(ArNC(Me)-(Me)CNAr)Pd(Me)(NCMe)]⁺(Ar = 2,6-(iPr)₂C₆H₃) (1), was first covalently immobilized onto two ordered mesoporous silicas (SBA-15 and MSU-F) containing surface-bound acryloyl functionalities to render the mesoporous silica-supported chelate Pd−diimine catalysts (Pd-SBA15 and Pd-MSUF, respectively). Surface-initiated ethylene polymerizations within mesopores were subsequently carried out with Pd-SBA15 and Pd-MSUF at an ethylene pressure of 400 psi and 5 °C. A mechanistic study on the polymerization behavior and the confining effects of silica meso-structures on polymer growth has been undertaken. The covalent surface-grafting of polyethylene within silica nanochannels was confirmed by the results from Fourier-transformed infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), nitrogen adsorption-desorption, electron microscopy, and proton nuclear magnetic resonance (¹H NMR). The content of grafted polyethylene in the composites can be adjusted in a wide range by varying polymerization time. This represents the first report on the covalent surface functionalization of mesoporous silicas with polyethylene via surface-initiated ethylene polymerization.     

Synthesis of C60 end-capped poly(4-diphenylaminostyrene): Addition of poly(4-diphenylaminostyryl)lithium to C60

The covalent modification of fullerene-C₆₀ (C₆₀) with poly(4-diphenylaminostyrene) (PDAS) was examined to explore the possibility of preparing new materials for effective photovoltaic cells. The high nucleophilicity and small steric hindrance of the PDAS carbanion is a very important factor in the addition of poly(4-diphenylaminostyryl)lithium (PDASLi) to C₆₀. C₆₀ end-capped PDAS (C₆₀-PDAS), consisting of one PDAS molecule bonded to one C₆₀ molecule at the polymer chain-end, was successfully prepared from the PDASLi/N,N,N’,N’-tetramethylethylenediamine system and C₆₀. UV/vis and photoluminescence spectra suggest that C₆₀-PDAS has considerable potential for the preparation of effective photovoltaic cells.     

Telechelic polyesters of ethane diol and adipic or sebacic acid by means of bismuth carboxylates as non-toxic catalysts

Dimethyladipate or dimethylsebacate were polycondensed with an excess of 1,2-ethane diol in bulk using two different temperature/time programs. Bismuth(III)n-hexanoate (BiHex₃), tin(II)2-ethylhexanoate (SnOct₂) and titanium tetrabutoxide were used as catalysts. Only the bismuth catalyst yielded clean telechelic polyesters having two ethylene glycol endgroups. With SnOct₂ cyclic oligoesters were obtained as byproducts. Ti(OBu)₄ yielded OH-terminated linear chains containing large amounts of diethylene glycol units (detectable up to three ether groups per chain). Furthermore, small amounts of cycles were also formed. Acid-catalyzed polycondensations of ethylene glycol with sebacic acid gave low yields of low oligomers, part of which contained diethylene glycol units.     

Hydrophilic and hydrophobic copolymers of a polyaspartylhydrazide bearing positive charges as vector for gene therapy

BACKGROUND: The design of polymeric vectors for gene delivery provided with specific properties is one of the most critical aspects for a successful gene therapy. These polymers should be biocompatible as well as able to carry efficiently DNA to target tissues and to transfect it into cells. RESULTS: The formation of complexes of poly[(α,β‐asparthylhydrazide)–poly(ethylene glycol)] and poly[(α,β‐asparthylhydrazide)–hexadecylamine] copolymers functionalised with glycidyltrimethylammonium chloride (PAHy–PEG‐GTA and PAHy–C₁₆‐GTA, respectively) with DNA was studied. The effects of the introduction of hydrophilic (PEG) or hydrophobic (C₁₆) moieties on the chains of PAHy–GTA copolymers, such as the stabilising effect on the DNA structure, were evaluated. In particular, we observed a high DNA protection by PAHy–PEG‐GTA copolymers. Degradation studies led us to suppose a particular aqueous conformation of the polyionic complex of PAHy–PEG₂₀₀₀‐GTA in which DNA should be internalised into an inner core surrounded by a PEG hydrophilic shell; while no significant protection was detected with PAHy–C₁₆‐GTA in which DNA should be disposed on the surface of the complex, freely exposed to DNase II action. CONCLUSION: The insertion of PEG or C₁₆ chains into the polymeric structure of PAHy–GTA copolymers changes significantly the DNA complexing and protecting ability of the PAHy–GTA copolymers, showing that hydrophilic and hydrophobic side chains can play a crucial role in supramolecular arrangements of interpolyelectrolyte complexes between DNA and PAHy copolymers. Copyright © 2008 Society of Chemical Industry     

Effect of alkali on filaments of poly(ethylene terephthalate) and its copolyesters. II. Presence of quaternary ammonium salt in the alkali-bath

Influence of alkyl (C₁₂–C₁₄)-dimethyl-benzyl ammonium chloride in the solution of sodium hydroxide on the hydrolysis of poly(ethylene terephthalate) (PET), anionically modified poly(ethylene terephthalate) copolyster (CDP), and block polymer of poly(ethylene terephthalate)-poly(ethylene glycol) (EDP), has been studied under a variety of proportions, concentrations, time and temperature of reaction, M : L ratio, etc. Mechanical properties of treated polymeric materials are evaluated. Hydrolysis of two polymers in the same bath is compared with that in separate baths.     

Solution thermodynamic study of several hydrocarbons in γ-butyrolactone and ethylene glycol mixtures by GLC

The gas—liquid chromatographic technique was used to determine the thermodynamic properties of solutions at infinite dilution for binary and ternary systems of five normal paraffins (C₅–-C₉), cyclohexane, benzene and toluene with γ-butyrolactone and ethylene glycol mixtures. A combination solvent of 50 mol % of γ-butyrolactone and ethylene glycol was shown to have the highest selectivity towards aromatic hydrocarbons.