Polyethylene Glycol Molecules Research Articles

INTERFERONS AND EYE DISEASES

The review contains an analysis of the medical use of interferons – a group of signaling protein molecules that have antiviral, antitumor, and immunomodulatory activity – in ophthalmic practice. Interferons have a wide spectrum of action, including antiviral, immunomodulatory, antitumor and other types of activity. This provides a great potential for interferon use in ophthalmology, both in combination and as a first-line therapy for conjunctival papillomatosis, squamous cell neoplasia, conjunctival melanoma, keratitis caused by the herpes simplex virus, uveitis, geographical choriopathy, cystic and diabetic macular edemas, etc. There are considered mechanism of action, dosing regimens, side effects of using interferons and such their solutions as use of newly discovered interferon lambda and interferon pegylation. In contrast to the ubiquitous expression of the IFN-α receptor, IFN-λ receptor is determined mainly in the epithelial cells of the mucous membranes and skin keratinocytes, which provides a more targeted effect of the drugs. Modifying the properties of biologically active substances by combining them with low molecular weight carriers, for example, polyethylene glycol molecules (PEG), leads to a decrease in the therapeutic dose of the drug and an increase in the selectivity of its action due to changes in pharmacokinetic and pharmacodynamic parameters.

Fabrication of nanoclay gel composite: A novel nanoclay masterbatch approach to nanocomposite preparation via melt extrusion process

The objective of this research was to fabricate a novel nanoclay masterbatch containing polymer‐intercalated in nanoclay with comparable degree of interlayer expansion, flowability, and high thermal stability. It is ready to use for preparing polymer/clay nanocomposites by melt extrusion. The nanoclay masterbatch was efficiently prepared in one‐step via a new approach called nanoclay gel. The nanoclay gels were successfully prepared at different original nanoclay concentrations ranging from low to high clay loading (10%, 20%, and 30% w/v) in cooperation with polyethylene glycol (PEG) at various PEG loadings (weight ratios of nanoclay/PEG 1/1, ½, and 1/3) and kappa carrageenan (KC), a thermolytic hydrogel at a fixed minimum concentration. X‐ray diffraction (XRD) results revealed that the intercalation of PEG molecules expanded silicate basal spacing up to 17–18 A° even at high percentage of nanoclay (dry content about 24–49 wt%). Scanning electron microscope (SEM) revealed the denser packing of clay layers in accordance to an increase in density of the dry nanoclay gel with increment of original nanoclay loadings. An increase of PEG content exhibited better flow ability as seen by increasing melt flow index. Thermal decomposition of the nanoclay gels was up to 380°C; by using the dry nanoclay gels to prepare polystyrene (PS)/clay nanocomposites via melt extrusion. The morphological results showed that the exfoliated structures were achieved. The mechanical and thermal stability properties were significantly enhanced. The appearing color of PS/clay nanocomposites prepared from nanoclay gel was bright pale‐yellow without evidence of thermal degradation. POLYM. COMPOS., 40:2751–2767, 2019. © 2018 Society of Plastics Engineers

Improvement in the Predicted Partitioning of Alcohol and Polyethylene Oxide Groups Between Water and Octanol (logP) in Molecular Dynamics Simulations

Molecular dynamics simulations can be applied to explore the complex liquid phase behavior of lipid-based formulations and the gastrointestinal tract lumen. In order for the results from these simulations to be of value, the manner in which molecules interact with both aqueous and oil phases present needs to be as correct as possible. An existing molecular dynamics force field, GROMOS 53a6, was demonstrated to poorly reproduce the partitioning of straight-chain alcohol and short-chain polyethylene glycol (PEG) molecules between octanol and water phase (logP), with the molecules too hydrophobic. Force field parameters for Lennard-Jones interactions between CH2 and CH3 with water oxygen were adjusted to reproduce the experimental octanol logP, with all other Lennard-Jones and force field parameters left untouched. This parameter set, called 53a6DBW, was subsequently used to recalculate straight-chain alcohol and short-chain PEG molecules, with significant improvement in the values obtained. Simulations of a nonionic surfactant in water, octaethylene glycol monocaprylate, were also performed to observe the aggregation behavior. 53a6DBW demonstrated significant improvements in water interactions with the PEG chains, well hydrating the PEG groups, and allowing the formation of micelles. Further improvements and evaluation of the improved parameter set are ongoing.

Electrochemical functionalization of polypyrrole nanowires for the development of ultrasensitive biosensors for detecting microRNA

A simple electrochemical patterning strategy has been developed for the construction of ultrasensitive biosensors based on polyethylene glycol (PEG)-polypyrrole (PPy) nanowires substrate in order to supply improved antifouling performances. PPy nanowires array was produced through electrochemical polymerization of pyrrole at constant potential onto glassy carbon electrode (GCE) surface. PPy nanowires surfaces were decorated with 4-armed PEG molecules by electrochemical oxidation of amine groups offered by PEG end chains. The prepared PEG/PPy nanowires have integrated the excellent electrical conductivity of conducting polymer PPy nanowires with the good antifouling property of PEG. MicroRNAs (miRNAs) play very important roles in cancer development and a variety of diseases, which make them become promising biomarkers of the onset, prognosis and risk of diseases. Therefore the establishment of miRNA profiles for diseases and the detection of miRNAs in biological samples are critical milestones in diagnostics. An ultrasensitive electrochemical biosensor for miRNA can be effortlessly developed by the immobilization of DNA probes onto PEG/PPy nanowires. DNA/RNA hybridization was monitored by changes of methylene blue (MB) redox signal using differential pulse voltammetry (DPV) method. A wide linear range (0.10 pM ∼ 1.0 nM) to target miRNA was obtained by the fabricated biosensor, and miRNA mismatches can also be easily identified with satisfactory. Furthermore, the biosensor based on PEG/PPy nanowires can be extended to the development of any type of DNA-based biosensor.

Highly Efficient Copper Sulfide-Based Near-Infrared Photothermal Agents: Exploring the Limits of Macroscopic Heat Conversion.

Among the foreseeable therapeutic approaches at the cellular level, nanoplatform-driven photothermal therapy is a thriving tool for the selective eradication of malignant tissues with minimal side effects to healthy ones. Hence, chemically versatile, near-infrared absorbing plasmonic nanoparticles are distinctly appealing and most sought after as efficient photothermal agents. In this work, a straightforward method to synthesize monodisperse PEGylated copper sulfide nanoparticles of pure covellite (CuS) phase, featuring strong localized surface plasmonic resonance absorption in the near-infrared and flexible surface chemistry, imparted by monomethyl ether polyethylene glycol molecules, is developed and optimized. These nanoparticles show a remarkable photothermal heat conversion efficiency (HCE) of 71.4%, which is among the highest for CuS systems and rivals that of plasmonic noble metal nanostructures. Moreover, through critical evaluation and mathematical modeling of the material's properties and measurement methodology, it is assessed that the calculated HCE values drastically depend on experimental conditions such as wavelength-dependent solvent absorption properties, sol concentration, and optical path. These findings are of paramount relevance to the photothermal community, since they call for a standardization of the procedure for the evaluation of the HCE of proposed photothermal agents, in order to make the reported values universally and reliably comparable.

PEGylated Gold Nanoparticles with Interesting Plasmonic Properties Synthesized Using an Original, Rapid, and Easy-to-Implement Procedure

In this letter, we report a new, one-step, rapid, and easy-to-implement method for the synthesis of PEGylated gold nanoparticles (PEG-AuNPs) having a narrow size distribution and very interesting plasmonic properties. Unmodified polyethylene glycol molecules with a molecular weight of 1000 g/mole (PEG1000) have been employed as reducing and capping agents for the synthesis of spherical gold nanoparticles having an average diameter of 35 nm, within a few minutes. The novelty of the herein proposed synthesis method consists in the fact that the synthesis takes place inside of a sealed bottle flask containing aqueous solutions of PEG1000, tetrachloroauric(III) acid (HAuCl4), and NaOH, placed in the center of a microwave oven, capable to provide a very uniform temperature environment. It turned out that, during the very short synthesis procedure (2 minutes), PEG 1000 suffers an oxidative transformation in such a manner that its terminal alcohol groups (-CH2-OH) are transformed in carboxylate ones (-COO−). The as-synthesized PEG-AuNPs possess very interesting plasmonic properties allowing the detection of different molecules by means of SER spectroscopy performed either in liquid droplets or on solid spots. As a consequence of their unique plasmonic properties, the SER spectra acquired using this new class of nanoparticles on different molecules of interest (methylene blue, rhodamine 6G, doxorubicin, and 5-fluorouracil) are highly reproducible, making them ideal candidates for further use as SERS substrates.

Polyethylene Glycol for LiFePO4/C Composites Preparation: Large or Small Molecular Weight

Olivine LiFePO4 is challenged by its poor electronic and ionic conductivities for lithium-ion batteries. Polyethylene glycol (PEG) has been applied for LiFePO4 preparation by different research groups, but there is no consensus on the influence of the mean molecular weight of PEG on the structure and electrochemical performances of LiFePO4/C composites. In this work, LiFePO4/C composites were prepared by using micronsized FePO4·2H2O powder as starting material, PEG (mean molecular weight of 200, 400, 4000 or 10000) and citric acid as complex carbon source. The structure and electrochemical performances of LiFePO4/C composites would be decided considerably by the mean molecular weight of PEG, and the sample using PEG200 exhibited the least inter-particle agglomeration, the smallest charge transfer resistance and the highest discharge capacity. A probable growth mechanism is also proposed based on SEM images and electrochemical results: with the assistance of citric acid, PEG molecule with small molecular weight tends to cover one or only a few micron-sized FePO4·2H2O particles, significantly suppress the agglomeration of primary LiFePO4 particles and thus result in uniform particle-size distribution and carbon coating.

Atomistic Modeling of Intrinsically Disordered Proteins Under Polyethylene Glycol Crowding: Quantitative Comparison with Experimental Data and Implication of Protein–Crowder Attraction

The malleability of intrinsically disordered proteins (IDPs) has generated great interest in understanding how their conformations respond to crowded cellular environments. Experiments can report gross properties such as fluorescence resonance energy transfer (FRET) efficiency but cannot resolve the conformational ensembles of IDPs and their interactions with macromolecular crowders. Computation can in principle provide the latter information but in practice has been hampered by the enormous expense for realistic modeling of IDPs and crowders and for sufficient conformational sampling. Here, taking advantage of a powerful method called FMAP (fast Fourier transform-based modeling of atomistic protein-crowder interactions), we computed how the conformational ensembles of three IDPs are modified in concentrated polyethylene glycol (PEG) 6000 solutions. We represented the IDPs at the all-atom level and the PEG molecules at a coarse-grained level and calculated the experimental observable, i.e., FRET efficiency. Whereas accounting for only steric repulsion of PEG led to overestimation of crowding effects, quantitative agreement with experimental data was obtained upon including mild IDP-PEG attraction. The present work demonstrates that realistic modeling of IDPs under crowded conditions for direct comparison with experiments is now achievable.

Noncovalent Pyrene-Polyethylene Glycol Coatings of Carbon Nanotubes Achieve in Vitro Biocompatibility.

Single-walled carbon nanotubes (SWNTs) have become increasingly exploited in biological applications, such as imaging and drug delivery. The application of SWNTs in biological settings requires the surface chemistry to remain through the low solubility in aqueous media. In this research, a facile approach for the preparation of a polyethylene glycol (PEG)-coated SWNT-based nanocarrier was reported. We focused on the effect of PEG chain length and SWNT size on the cytotoxicity of PEG-coated SWNTs as a superior drug delivery nanovector. First, all-atom molecular dynamics (MD) simulations were employed to explore the stability and behavior of SWNT/pyrene-PEG (SWNT/Pyr-PEG) structures at a molecular level that is not attainable with experiments. The MD studies revealed that (i) π-π stacking interactions between the pyrene bearing PEG molecules and SWNTs are maintained in bulky situations, regardless of PEG molecular weight or SWNT size; (ii) pyrene molecules diffuse over the SWNT surface without detaching; and (iii) both short and long dynamic Pyr-PEG chains have the capability of effectively coating the SWNT surface. In light of the simulations, noncovalent (π-π stacking) assemblies of SWNT/Pyr-PEG with different molecular weights of PEG ( Mw = 2000, 5000, and 12000) were successfully fabricated and characterized. For longer PEG chains, more effective coating of SWNTs was obtained, resulting in more biocompatible SWNT/Pyr-PEG nanomaterials. The number of SWNTs coated by Pyr-PEG was highly dependent on the length of pyrene bearing PEG polymers. Moreover, the short SWNTs showed a higher amount of PEG coating with respect to the long SWNTs. Cell viability results demonstrated a dose-dependent cytotoxicity of coated SWNTs. Short SWNTs coated with longer PEG chains have low cytotoxicity to be used in in vivo studies.

Effects of Protein Corona on Active and Passive Targeting of Cyclic RGD Peptide-Functionalized PEGylation Nanoparticles.

Protein corona can alter the physiochemical properties of targeting nanoparticles (NPs), as well as their physiological responses and targeting functionality. Herein, we synthesized 20 types of NPs with diverse surface chemistry in order to study the impacts of protein corona on targeting functionality of NPs functionalized with cyclic RGD peptides and their relationships to the polyethylene glycol (PEG) length and grafting density of targeting ligands. After protein adsorption, cyclic RGD on the surface of NP was still able to bind its receptors with increased targeted cellular uptake, even at a relatively low density. However, the cellular uptake was reduced from 26 to 76% when compared with protein nonbound NPs, which was caused by the shielding effect of the outer layer adsorbed proteins. NPs functionalized with short PEG molecules and moderate cyclic RGD density performed a better targeting efficiency. Due to PEG conjugation, the protein corona was demonstrated to be beneficial for passive targeting by decreasing macrophage cellular uptake. These relationships between surface chemistry and targeting functionality will provide guidelines for the design of targeting nanoformulations in nanomedicine.

Multi-Layer Filters: Adsorption and Filtration Mechanisms for Improved Separation.

Filters made of cellulose fiber and perlite particles were prepared using a wet laying papermaking technique. Polyamide-amine-epichlorohydrin (PAE) was added to provide wet strength. Filters were prepared at two different total basis weights of 200 and 400 grams per square meter (gsm). Single and multi-layered filters were structured for each total basis weights. The effect of total basis weights and multi-layered structure on methylene blue adsorption and silicon dioxide (SiO2) particle filtration was investigated. Methylene blue adsorption was performed in two modes: constant pressure and constant flow rate. In both operation modes, the adsorption capacity of multi-layered filters was significantly higher (16–100%) than for single-layer filters at the same overall weight. The effect of layer separation was also characterized using polypropylene separators and tested under constant flow rate operation. Separators provided more effective methylene blue adsorption by generating a well-distributed flow. Filtration performance was quantified with 0.5 μm silicon dioxide particles under constant pressure conditions; this is to mimic bacteria rejection. Filtration capability of SiO2 particles was reduced slightly (12%) with decreasing individual filter layer thickness regardless of the multi-layered structure. Filtering polyethylene glycol (PEG) molecules with two different molecular weights was performed; however, no rejection was recorded. The filter internal pore structure was visualized by 3D-X ray computed tomography and the void fraction was quantified. 400 gsm single layer presented areas of low fiber density forming pores, while the pore volume decreased for thinner filter layers.

Effects of core size and PEG coating layer of iron oxide nanoparticles on the distribution and metabolism in mice.

IntroductionIn vivo distribution of polyethylene glycol (PEG)ylated functional nanoparticles is vital for determining their imaging function and therapeutic efficacy in nanomedicine. However, contradictory results have been reported regarding the effect of core size and PEG surface of the nanoparticles on biodistribution.MethodsTo clarify this ambiguous understanding, using iron oxide nanoparticles (IONPs) as a model system, we investigated the effect of core size and PEG molecule weights on in vivo distribution in mice. Three PEGylated IONPs, including 14 nm IONP@PEG2,000, 14 nm IONP@PEG5,000, and 22 nm IONP@PEG5,000, were prepared with a hydrodynamic size of 26, 34, and 81 nm, respectively. The blood pharmacokinetics and tissue distribution were investigated in detail.ResultsThe results indicated that the PEG layer, rather than core size, played a dominant role in determining the half-life time of IONPs. Specifically, increased molecular weight of the PEG layer led to a longer half-life time. These PEGylated IONPs were mainly excreted by liver clearance. While the PEG molecular layer constituted the key factor to determine the clearance ratio, core size affected the clearance rate.ConclusionComplete blood count analysis and histopathology suggested excellent biocompatibility of PEGylated IONPs for future clinical trials.

Application of steric exclusion chromatography on monoliths for separation and purification of RNA molecules

Steric exclusion chromatography (SXC) is a method for separation of large target solutes based on their association with a hydrophilic stationary phase through mutual steric exclusion of polyethylene glycol (PEG). Selectivity in SXC is determined by the size or shape (or both) of the solutes alongside the size and concentration of PEG molecules. Elution is achieved by decreasing the PEG concentration. In this study, SXC applicability for the separation and purification of single-stranded (ss) and double-stranded (ds) RNA molecules was evaluated for the first time. The retention of ssRNA and dsRNA molecules of different lengths on convective interaction media (CIM) monolithic columns was systematically studied under variable PEG-6000 and NaCl concentrations. We determined that over 90% of long ssRNAs (700–6374 nucleotides) and long dsRNAs (500–6374 base pairs) are retained on the stationary phase in 15% PEG-6000 and ≥0.4 M NaCl. dsDNA and dsRNA molecules of the same length were partially separated by SXC. Separation of RNA molecules below 100 nucleotides from longer RNA species is easily achieved by SXC. Furthermore, SXC has the potential to separate dsRNAs from ssRNAs of the same length. We also demonstrated that SXC is suitable for the enrichment of ssRNA (PRR1 bacteriophage) and dsRNA (Phi6 bacteriophage) viral genomes from contaminating cellular RNA species. In summary, SXC on CIM monolithic columns is an appropriate tool for rapid RNA separation and concentration.

In situ functionalization of gadolinium oxide nanoparticles with polyethylene glycol (PEG) by pulsed laser ablation in a liquid medium (PLAL)

Abstract Gadolinium oxide (Gd2O3) nanoparticles with paramagnetic properties and biocompatible surfaces are promising materials for bioimaging applications. We synthesized in situ pegylated Gd2O3 (Gd2O3@PEG) nanoparticles by liquid phase pulsed laser ablation (PLAL) of a gadolinium target in a polyethylene glycol (PEG) liquid medium. We characterized their shape and morphology using transmission electron microscopy (TEM), and confirmed their crystalline structure with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy (EDX) elemental mapping. The magnetic properties of the nanoparticles were characterized by vibrating sample magnetometry (VSM). We have found that the crystalline nanoparticles generated have a spherical shape and a narrow distribution with average diameters of 15.0, 11.6, and 6.0 nm, for PEG concentrations of 0.01, 0.05, and 0.10 mM, respectively. We verified that partially oxidized molecules of PEG are attached to the nanoparticle surface as carboxyl groups. An analysis of the magnetization of Gd2O3@PEG nanoparticles revealed highly paramagnetic properties. Consequently, PLAL forms a green synthesis of Gd2O3@PEG, opening up new opportunities for bioimaging applications.

Transferrin Adsorbed on PEGylated Gold Nanoparticles and Its Relevance to Targeting Specificity.

Polyethylene glycol (PEG) has been frequently used for surface modification of nanoparticles (NPs) to reduce non-specific binding of proteins on NPs. The investigation of protein absorption on PEGylated nanoparticles is necessary. In the work, the conjugation of transferrin (Tf) to PEGylated AuNPs via adsorption or bonding was studied. The 13 nm AuNPs were coated with various molecular weight (300, 2000, 5000) carboxyl and methoxy PEG thiol. The presence of Tf on PEGylated AuNP was characterized by dynamic light scattering (DLS) and infrared spectroscopy (IR). The data of IR confirmed the presence of Tf on PEGylated AuNPs. The diameter decrease of PEGylated AuNPs after Tf adsorption was observed by DLS measurement, which is attributed to competitive adsorption between Tf and PEG molecules. These phenomena may be important to the preservation of Tf targeting specificity on PEGylated AuNPs.

Effect of PEI surface modification with PEG on cytotoxicity and transfection efficiency

Polyethylenimine (PEI) is a cationic polymer with high transfection efficiency as non-viral gene delivery agent that exhibits promising features for gene therapy applications due to its cationic charge and thus favourable DNA-condensing abilities; however, its high cytotoxicity restricts its application. The cellular toxicity of PEI molecules depends on their structure, molecular weight and surface charge density. To improve the properties of branched 25 kDa PEI as a non-viral gene delivery agent, this polymer was conjugated to polyethylene glycol (PEG) molecules at three different molar ratios of 10, 20 and 30. The degree of PEG grafting was determined by 2, 4, 6-trinitrobenzene sulphonic acid assay. The effects of various PEGylation degrees on cellular toxicity and transfection ability of PEI polymer were assessed on BT-474 and MCF-10A cell lines. Compared to unmodified PEI, PEG-grafted PEI copolymers demonstrated reduced cytotoxicity, particularly at higher PEG grafting ratios. Among different PEG-grafted PEIs, the PEG-PEI copolymer which grafted to PEG at a molar ratio of 10:1 had the highest transfection efficiency in both cell lines. The findings of this Letter showed that these PEG-grafted PEI copolymers have desirable gene transfection efficiency and favourable biocompatibility for gene delivery.

Fluorescence techniques can reveal cell wall organization and predict saccharification in pretreated wood biomass

The conversion of cell wall biomass to sugar for fermentation to ethanol requires chemical or physical pretreatments to disrupt the recalcitrant plant cell walls and to make the cellulose accessible to cellulolytic enzymes. Multiscale study of biomass deconstruction gives access to key insights into the cell wall and lignin changes induced by pretreatment. Few studies have compared the effect of pretreatment of different biomass species on the cell wall accessibility.Considering representative softwood (pine) and hardwood (poplar) biomass, we studied the impact of two pretreatments on enzymatic saccharification and cell wall structure and accessibility. Lignin fluorescence properties were investigated by measuring fluorescence lifetime in addition to chemical analysis, and the accessibility of biomass was assessed using fluorescent probes consisting of rhodamine labeled polyethylene glycol (PEG) molecules ranging from 10 to 40 kDa. Hot water treatment and chlorite delignification altered chemical structure and fluorescence lifetime, which was positively correlated with glucose conversion and negatively correlated with lignin and β-O-4′ contents. Imaging distribution of the probes indicated that chlorite pretreatment resulted in a more uniform distribution of probe in the cell wall compared to hot water treatment. The interaction between cell wall and fluorescent PEG probes was evaluated using Förster Resonance Energy Transfer (FRET) and fluorescence microscopy. The FRET efficiency showed a high negative correlation with the probe size and was greatly increased by chlorite delignification, reflecting increased accessibility to the probe and interaction. Thus the accessibility and interactions of small probes in pretreated biomass could be a relevant indicator of potential for saccharification, whereas fluorescence lifetime provides a new criteria for assessing relevant cell wall structural modifications related to enzymatic conversion of lignocellulosic biomass.

Synthesis and characterization of chain-extended and branched polyurethane copolymers as form stable phase change materials for solar thermal conversion storage

In this work, polyethylene glycol (PEG) based polyurethane copolymer was synthesized using linear chain extension and branching methods. In linear chain extension, multiple PEG molecules were linked using urethane bonds. In branching, polyvinyl alcohol (PVOH) backbone was grafted with PEG molecules as branches and cross-linked to other PVOH molecules. 4,4′-Diphenylmethane di-isocyanate (MDI) was used as both chain extender and cross-linker. The resulting copolymers were characterized for chemical composition, microscopic morphology, crystalloid structure and thermal properties. Based on the results from characterizations, a detailed discussion on the phase change mechanism in polyurethanes is presented. 1H NMR and FT-IR results confirmed the chain extension and branching. 1H NMR spectra displayed characteristic signal of the urethane. DSC results revealed solid-solid phase change behavior of copolymers with high latent heat. Crystalline nature of spherulite lamellae structures was verified by observing birefringence using POM microscope and XRD peaks. Polyurethane copolymers had maximum latent heat absorption capacity of 144.14 kJ kg−1 at melting temperature of 51 ℃ and had maximum heat release capacity of 117.5 kJ kg−1 at freezing temperature of 33 ℃. Polyurethane copolymers were thermally stable up to 200 ℃. Polyurethane copolymers satisfied all criteria for use as form stable solid-solid phase change material (SSPCM) in solar thermal conversion storage.

High Performance Shape-Stabilized Phase Change Material with Nanoflower-Like Wrinkled Mesoporous Silica Encapsulating Polyethylene Glycol: Preparation and Thermal Properties.

Nanoflower-like wrinkled mesoporous silica (NFMS) was prepared for further application as the carrier of polyethylene glycol (PEG) to fabricate the new, shape-stabilized phase change composites (PEG/NFMS); NFMS could improve the loading content of PEG in the PEG/NFMS. To investigate the properties of PEG/NFMS, characterization approaches, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) analysis, and differential scanning calorimetry (DSC), were carried out. The characterization results illustrated that the PEG was completely adsorbed in the NFMS by physical adsorption, and the nanoflower-like wrinkled silica did not affect the crystal structure of PEG. As reported by the DSC test, although NFMS had a restriction influence on the activity of the PEG molecules, the melting and binding enthalpies of the PEG/NFMS could reach 136.6 J/g and 132.6 J/g, respectively. In addition, the TGA curves demonstrated that no evident weight loss was observed from 20 °C to 190 °C for the PEG/NFMS, and the results revealed that the PEG/NFMS had remarkable thermal stability. These results indicated that the NFMS is a potential carrier of organic phase change material for the preparation of shape-stabilized phase change composites.

The effect of capping agents on the structural and magnetic properties of cobalt ferrite nanoparticles

Microwave-assisted co-precipitation method was adopted to analyze the effect of polyethylene glycol (PEG) and urea concentrations on the properties of cobalt ferrite nanoparticles (NPs). The average crystallite size of single phase cubic spinel cobalt ferrite NPs was controlled within 10–14 nm with the effect of PEG, urea and the combination of them. The transmission electron micrographs revealed that the morphology of cobalt ferrites was not significantly influenced by the different concentration of capping agents but almost uniform morphology with nearly narrow size distribution was obtained. The interaction of PEG and urea molecules on the surface of nanoparticles was mediated through –OH hydroxyl group affected the crystal growth rate. The possible interaction mechanism was proposed with the help of IR vibrational spectra. All the samples exhibited ferromagnetism at room temperature and it was found that the capping agents showed an effect on the magnetic properties. The maximum saturation magnetization of 58 emu/g was achieved when the urea of 60 mg was used and the maximum coercivity of 311 Oe was attained when the mixture of PEG (40 mg) and urea (20 mg) were used. Ultrafine and hydrophilic cobalt ferrite NPs that showed appreciable magnetic properties obtained in the present experimental procedure would be of great interest in various biomedical applications.