Synthesis and characterization of poly(ethylene glycol) based β-cyclodextrin polymers

A series of novel water soluble β-cyclodextrin (βCD) polymers has been synthesized from functionalized poly(ethylene glycol) (PEG). The chemical composition of the polymers has been characterized by ¹H NMR and the βCD content is found to be between 48 and 33% (w/w). The molecular weight has been determined by Size Exclusion Chromatography (SEC) and depends on the ratio between βCD and PEG, varying from 2.1 × 10⁴ to 8.6 × 10⁴ g mol^?1. The physico chemical properties have been characterized by differential scanning calorimetry (DSC), viscometry and isothermal titration calorimetry (ITC). ITC shows that the polymers have association constants comparable to βCD with different guest molecules, indicating a good accessibility of the CDs.     

Thermo-physical properties of pure ethylene glycol and water–ethylene glycol mixture-based boron nitride nanofluids

Journal of Thermal Analysis and Calorimetry - Nanofluids are suspensions of solid nanoparticles in conventional heat transfer fluids, and they often exhibit improved heat transfer characteristics....     

Studies on photocatalytic performance and photodegradation kinetics of zinc oxide nanoparticles prepared by microwave-assisted sol–gel technique using ethylene glycol

ZnO nanoparticles with an average particle size of 27 nm were fabricated using a microwave-assisted sol–gel method in the presence of ethylene glycol. The nanoparticles were characterized by X-ray diffraction, Monshi’s equation, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. The band gap energy of the nanoparticles was measured to be 3.27 eV by UV–Vis absorption and reflection spectroscopy. Photocatalytic activity of the synthesized nanoparticles was assessed by degrading nitrophenol in aqueous solution under UV-C irradiation. The effects of initial nitrophenol concentration, amount of photocatalyst, and of pH on the photodegradation process were investigated. Degradation samples were analyzed by UV–Vis spectroscopy. Nitrophenol was removed by 98 % within 240 min. The degradation kinetics were studied and fitted well to pseudo-first-order and Langmuir–Hinshelwood models.     

Investigation of the thermal properties of glycidyl methacrylate–ethylene glycol dimethacrylate copolymeric microspheres modified by Diels–Alder reaction

Journal of Thermal Analysis and Calorimetry - The study describes the thermal properties of functional microspheres composed of glycidyl methacrylate (GMA) and crosslinking agent ethylene glycol...     

Formation,structure and thermal properties of the ternary aggregate of polyethylene glycol, β-cyclodextrin and ferrocene

In this study, we firstly describe the formation of a ternary aggregate of ferrocene (Fc), polyethylene glycol (PEG) and β-cyclodextrin (β-CD). Our results provide strong evidence for the fact that the intermolecular aggregation behaviour leads to a striking change in structure and thermal property of the components aggregated. First of all, several independent experiments give us sufficient information about the structure of the aggregate: (1) the ternary aggregate tends to form a uniform fine-grained sponge structure, generating small particles with higher surface areas; (2) there is a threading mechanism of the PEG chain into the cavities of β-CD, and Fc plays the role of a stabiliser for such an aggregation; (3) there is a continual decrease in electron density of the Fe 2p3/2 region from free Fc to the binary aggregates of Fc and to the ternary aggregate. Next, the ternary aggregate exhibits a one-step degradation mechanism and has much lower thermal stability than free components and especially the physical mixture of the components. We believe that these findings are important and valuable for designing and fabricating polypseudorotaxanes, soft matters and organic/inorganic composite materials.     

The enhancement on thermal stability and charring–forming capability of nitration group

Lipid nanoparticles, both solid lipid nanoparticles and nanostructured lipid carriers (NLC), containing tacrolimus (FK) were obtained by solvent diffusion method associated with ultrasonication using stearic acid (SA) or beeswax as solid lipid. The oleic acid was used as liquid lipid in the NLC. Lipid nanoparticles were characterized by determining the drug loading, particle size, polydispersity index (PDI) and zeta potential (ZP). Analysis by differential scanning calorimetry and X-ray diffraction were performed. Lipid nanoparticles presented nano-sized from 139 to 275 nm. The PDI results show the particles present from 0.3 to 0.5, and ZP was higher than |25| mV. Drug loading ranged of 2.3–3.2%. SA nanoparticles presented better ZP, average size and distribution. However, beeswax nanoparticles showed higher drug loading. Results suggest there are no incompatibilities between FK and the raw materials. Polymorphic modifications were not observed. The results presented show that lipid nanoparticles using both lipids were successfully obtained and may represent promising delivery system of FK in topical formulations.     

Preparation and Characterization of Chitosan Composite Membranes Crosslinked by Carboxyl-capped Poly（ethylene glycol）

In this study a series of chemically crosslinked chitosan/poly（ethylene glycol） （CS/PEG） composite membranes were prepared with PEG as a crosslinking reagent other than an additional blend. First, carboxyl-eapped poly（ethylene glycol） （HOOC-PEG-COOH） was synthesized. Dense CS/PEG composite membranes were then prepared by casting/evaporation of CS and HOOC-PEG-COOH mixture in acetic acid solution. Chitosan was chemically crosslinked due to the amidation between the carboxyl in HOOC-PEG-COOH and the amino in chitosan under heating, as confirmed by FTIR analysis. The hydrophilicity, water-resistance and mechanical properties of pure and crosslinked chitosan membranes were characterized, respectively. The results of water contact angle and water absorption showed that the hydrophilicity of chitosan membranes could be significantly improved, while no significant difference of weight loss between pure chitosan membranes and crosslinked ones was detected, indicating that composite membranes with amidation crosslinking possess excellent water resistanance ability. Moreover, the tensile strength of chitosan membranes could be significantly enhanced with the addition of certain amount of HOOC-PEG-COOH crosslinker, while the elongation at break didn＇t degrade at the same time. Additionally, the results of swelling behaviors in water at different pH suggested that the composite membranes were pH sensitive.     

Characterization of nanoporous β-SiC fiber complex prepared by electrospinning and carbothermal reduction

The nanoporous β-silicon carbide (SiC) nano-sized fiber complex were made from precursors of various ratios with (SiO₂) as silicon source and polyacrylonitrile as carbon source by simple electrospinning method and economical carbothermal reduction. The prepared samples were characterized by SEM for surface shape, XRD for crystalline properties, TGA in air for oxygen resistance, and BET for porosity according to the precursor components (C/Si mol ratio). The samples with carbon ratio to silicon (C/Si) of five or more in the precursor showed the long fiber shape. Increasing the C/Si in the precursor solution tended to lead higher β-SiC crystalline and smaller crystallite size than low C/Si in the precursor solution because excess carbon could act as a dispersant and barrier to prevent neck growth or adhesion of SiC. The prepared samples have superior oxidation resistance as a whole. The increment of the C/Si leads to the increment of porosity. Also, it seems that the gaseous pore development of carbon during carbothermal reduction leads to mainly small pores (micro- or mesopores).     

Effect of ZnO nanoparticles on kinetics of thermal degradation and final properties of ethylene–propylene–diene rubber systems

The morphology, thermal degradation behavior in addition to static and dynamic mechanical properties of various ethylene?Cpropylene?Cdiene (EPDM) rubber compounds containing nano-zinc oxide (NZnO) were investigated compared to those of EPDM with ordinary-sized ZnO (OSZnO). The field-emission scanning electron microscopy studies showed that unlike the conventional system, the formation of large size ZnO agglomerates was discouraged for NZnO filled systems. Thermogravimetric analysis (TG) revealed that the thermal degradation of EPDM system was delayed upon the inclusion of NZnO instead of OSZnO in the compound. The kinetic analysis of TG data based on Friedman and Kissinger methods showed that the nanocomposite samples exhibited higher activation energy (E _a ) and lower order of reaction (n) over the conventional system, suggesting the enhancement of thermal stability upon decreasing ZnO particle size. The results obtained from dynamic mechanical analysis and static mechanical characterizations in terms of hardness, resilience, and abrasion tests interestingly indicated that NZnO not merely could act as a thermal insulator, but also could perform as a nano-filler to improve the final performance of EPDM elastomers.     

Comparison of the results of thermal denaturation of β-lactoglobulin obtained by DSC and UV-spectroscopy

The thermal denaturation of β-lactoglobulin in the presence of urea and alkylurea solutions were measured. In the presence of a high concentration of urea this protein shows not only heat but also cold denaturation. For studying the effect of temperature two methods were used, differential scanning calorimetry (DSC) and UV-spectroscopy. DSC provides direct model-independent determination of the transition enthalpy in comparison with UV-spectroscopy, which gives only apparent or van't Hoff enthalpy of transition. The UV-melting curves were analyzed on the basis of a two-state approximation. The apparent standard enthalpies of thermal denaturation, ΔH _app. ^o , were compared with calorimetric ones.     

Solubility enhancement of triflumizole by host-guest interaction with β-cyclodextrin

Summary The solubility enhancement of triflumizole, a systemic fungicide, by -cyclodextrin inclusion complexation was investigated by electron absorption spectroscopy. The respective association constant determined by different methods was estimated to 470±20M ^–1 in aqueous solution. A model for the host-guest complexation was deduced by molecular calculations.

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Löslichkeitsverbesserung von Triflumizole durchHost-Guest-Complexierung mit -Cyclodextrin

Zusammenfassung Die Löslichkeitsverbesserung des systemischen Fungizids Triflumizole durch Komplexierung mit -Cyclodextrin wurde mittels Elektronenabsorptionsspektroskopie untersucht. Die entsprechende Stabilitätskonstante wurde durch verschiedene Methoden erfaßt und betrug im wäßrigen Medium 470±20M ^–1. Ein Model für denHost-Guest-Complex wurde durch Molekülrechnungen erstellt.

     

Formation of acridones by ethylene extrusion in the reaction of arynes with β-lactams and dihydroquinolinones

N-Unsubstituted β-lactams react with a molecule of aryne by insertion into the amide bond to form a 2,3-dihydroquinolin-4-one, which subsequently reacts with another molecule of aryne to form an acridone by extrusion of a molecule of ethylene. 2,3-Dihydroquinolin-4-ones react under the same reaction conditions to afford identical results. This is the first example of ethylene extrusion in aryne chemistry.     

Microwave-Assisted Synthesis of Poly(ε-caprolactone)-block-poly(ethylene glycol) and Poly(lactide)-block-poly(ethylene glycol)

Summary: This study reported the preparation and characterization of PCL-b-mPEG (poly(ε-caprolactone)-block-poly(ethylene glycol)) and PLL-b-mPEG (poly(L-lactide)-block-poly(ethylene glycol)) diblock copolymers by microwave heating and comparison of resulted products the ones with prepared by conventional heating. Diblock copolymers were synthesized successfully by the microwave-assisted ROP in the presence of stannous octoate (SnOct₂) as catalyst under nitrogen atmosphere in different monomer ratios. Structural and functional characterization of copolymers were performed by FTIR, ¹H-NMR and DSC. Molecular weight values were determined by GPC and also calculated from ¹H-NMR. According to the results, microwave irradiation allowed to obtain polymers with very narrow size distribution in very short reaction time. Similar polymers prepared by conventional heating were also synthesized for comparison. Molecular weight and conversion of polymers were increased by irradiation time. This change was continued until a certain time point after which no more increase was observed. It was concluded that microwave irradiation is a succesful method to obtain these diblock copolymers in very short reaction time and with a similar conversion obtained by conventional method.     

The experimental investigation concerning the heat transfer enhancement via a four-point star swirl generator in the presence of water–ethylene glycol mixtures

Journal of Thermal Analysis and Calorimetry - In the present study, a new swirling flow generator is studied which aims to enhance the convective heat transfer rate in a heat exchanger tube. This...     

Synthesis and characterization of alternating fluorene–thiophene copolymers bearing ethylene glycol side-chains

Abstract  

New alternating fluorene–thiophene copolymers are introduced bearing polar ethylene glycol-carboxylate functionalities on the thiophene ring to achieve enhanced solubility in polar solvents. Suzuki polycondensation was applied to synthesize a set of three polymers with differing lengths of the ethylene glycol side-chains. The polymers are thermally stable up to temperatures of 300 °C. Solutions of the polymers in CHCl₃ show an absorption maximum at approximately 397 nm and a luminescence maximum of 472 nm in solutions with quantum yield of 30%. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels have been determined to be at −5.7 and −2.6 eV, respectively.     

Synergistic enhancement of the fluorescence intensity of 4,5-benzopiaselenol by surfactants and β-cyclodextrin in aqueous solution

The synergistic enhancement of the fluorescence intensity of 4,5-benzopiaselenol (I _F ^Se-DAN ) by surfactants (Sf) and -cyclodextrin (-CD) has been studied. The (I _F ^Se-DAN ) in sodium dodecyl sulfate (SDS)//gb-CD was approximately 30 times greater than that in water, and 5–6 times greater than that in either SDS or -CD solutions alone, and a blue-shift of the emission wavelength was observed.¹H-NMR experiments and determination of CMC values of Se-DAN/-CD, Se-DAN/SDS, and Se-DAN/SDS/-CD systems reveal that the synergistic fluorescence enhancement was produced by the SDS monomer/-CD inclusion complex. In essence, the synergistic enhancement is due to the altered microenvironment experienced by Se-DAN upon its transfer from water to the hydrophobic cavity upon complexation.     

Mechanical enhancement of melt-stretched β-nucleated isotactic polypropylene: The role of lamellar branching of β-crystal

Melt-stretched isotactic polypropylene (iPP) filled with different weight fractions (0, 0.1, 0.2 and 0.4 wt %) of β-nucleating agent (β-NA) was extruded via a single screw extruder with a slit die and immediately melt-stretched at the die exit. The microstructure and mechanical properties (i.e., monotonic tensile, step-cycle and stress relaxation behavior) of these samples were analyzed. Unexpectedly, the lamellar branching of β-crystal, which is similar to lamellar branching of α-crystal, is observed in melt-stretched β-nucleated iPP. More interestingly, it is found that, compared with other samples, iPP containing 0.2 wt % of β-NA has the best mechanical properties. Through thorough analysis of various structural characterizations, the improved tensile strength obtained from step-cycle tests and viscous force obtained from stress relaxation measurements for iPP with 0.2 wt% of β-NA is ascribed to lamellar branching of β-crystal. The study is an example of preparing high performance polymers via practical polymer processing methods.