Apparent Hydrodynamic Radius Research Articles

Development of a Multifunctional Oral Dosage Form via Integration of Solid Dispersion Technology with a Black Seed Oil-Based Self-Nanoemulsifying Drug Delivery System.

Lansoprazole (LZP) is used to treat acid-related gastrointestinal disorders; however, its low aqueous solubility limits its oral absorption. Black seed oil (BSO) has gastroprotective effects, making it a promising addition to gastric treatment regimens. The present study aims to develop a stable multifunctional formulation integrating solid dispersion (SD) technology with a bioactive self-nanoemulsifying drug delivery system (SNEDDS) based on BSO to synergistically enhance LZP delivery and therapeutic effects. The LZP-loaded SNEDDS was prepared using BSO, Transcutol P, and Kolliphor EL. SDs were produced by microwave irradiation and lyophilization using different polymers. The formulations were characterized by particle apparent hydrodynamic radius analysis, zeta potential, SEM, DSC, PXRD, and in vitro dissolution testing. Their chemical and physical stability under accelerated conditions was also examined. Physicochemical characterization revealed that the dispersed systems were in the nanosize range (<500 nm). DSC and PXRD studies revealed that lyophilization more potently disrupted LZP crystallinity versus microwave heating. The SNEDDS effectively solubilized LZP but degraded completely within 1 day. Lyophilized SDs with Pluronic F-127 demonstrated the highest LZP dissolution efficiency (3.5-fold vs. drug) and maintained chemical stability (>97%) for 1 month. SDs combined with the SNEDDS had variable effects suggesting that the synergistic benefits were dependent on the formulation and preparation method. Lyophilized LZP-Pluronic F127 SD enabled effective and stable LZP delivery alongside the bioactive effects of the BSO-based SNEDDS. This multifunctional system is a promising candidate with the potential for optimized gastrointestinal delivery of LZP and bioactive components.

Unraveling anomalous dispersion, and hydrophobic aggregation of zein nanoparticles

A comprehensive investigation was carried out to probe the dispersion and self-aggregation profile of nitrogen deficient hydrophobic protein, zein, in ethanolic solutions at pH= 4 away from its isoelectric pH (=6.2). Further, the turbidity measurements clearly established the values for CEOH-C, CEOH-ϕ, CEOH-max and CEOH-Prep which characterized the initiation of intramolecular folding, and intermolecular soluble aggregate formation, formation of largest size of aggregates, and the subsequent insoluble micro-aggregate formation, respectively, which was authenticated from DLS and SEM data. Thus, zein molecules were observed to undergo a series of morphological transformations solely dependent on the solvent hydrophobicity. It was remarkable to note that in the region CEOH-C ≤ CEOH ≤ CEOH-ϕ, the dispersion viscosity, and apparent hydrodynamic radius and zeta-potential of the nanoparticles exhibited anomalous linear relationship with CEOH. In conclusion, it is demonstrated that adjusting the solvent's hydrophobicity is the only way to alter the shape of zein nanoparticles and their hydrophobically induced self-aggregation.

Dilution Driven Self-assembly and Re-entrant Phase Transition in Molecular Hydrogels

TX-100 molecular hydrogels exhibited re-entrant melt-gel-sol phase transition driven solely by dilution, which sequentially altered the self-assembly of the micellar formations and their population was investigated through the monitoring of the physical parameters namely, solution viscosity, particle size histogram, ergodicity, and gel rigidity modulus. This phenomenon was noticed at 20°C in the TX-100 concentration region of 0.2 to 1.2 M much above the critical micellar concentration of 0.22 mM. The particle size histograms revealed the presence of spherical micelles (size »3 nm) in the solution ([TX-100] &lt; 0.5 M) which formed entangled wormlike cylindrical micelles (apparent hydrodynamic radius » 50 nm) when (0.5 M&lt; [TX-100] &lt; 0.9 M) giving rise to a gel-like structure. Further increase in the TX-100 concentration increased the propensity of these wormlike cylindrical micelles that got randomly distributed creating a dense melt phase. Interestingly, we observed transition solely driven by dilution which defined complete re-entrant behavior at room temperature. These molecular gels could be created by dilution of the melt or concentration of the sol unlike in the polymer gels. Remarkably, this hitherto little known unique phenomenon was exhibited by a simple system of non-ionic surfactant solution. Thus, we have a hydration reversible gel at our disposal which has a special place in soft matter arena.

Physicochemical mechanism of BSA, Hb, and dsDNA biomacromolecules with aq-NaCMC at 298.15–310.15 K interfaced with UV–vis fluorescence circular dichroism spectroscopy and in-silico for interacting activities

The 0.2–0.8mg% @ 0.2 mg% bovine serum albumin (BSA 66), hemoglobin (Hb 64.5), and double stranded deoxyribonucleic acid (dsDNA 130 kDa) with water and 0.25, 0.50, and 1.00 g% aqueous carboxymethyl cellulose sodium salt (NaCMC) thermodynamically, kinetically, and tentropically stable homogeneous solutions via resonating energy transfer were designed. Density (ρ), viscosity (η), surface tension (γ), friccohesity (σ), Gibbs free energy (ΔGb), chemical potential (μ), frictional volume (ϕ), apparent molar volume (V2), hydrodynamic radius (Rh), and isentropic compressibility (ksϕ) at 298.15, 304.15, and 310.15 K were studied. UV–Vis spectrophotometry, fluorescence spectroscopy, circular dichroism (CD), MALDI TOF, and in-silico study via reorientational activities have elucidated structural recognition. The ρ, η, γ, σ, ΔGb, μ, V2, ϕ, Rh, and ksϕ physicochemical properties (PCPs) have studied the interacting activities of salt bridges (peptide bonds) of proteins and base pairs (adenine, thymine, cytosine, guanine) of dsDNA on developing nanohydration sphere (NHS) with water and 0.25, 0.50, and 1.00 g% aq-NaCMC. Regression constants of PCPs have elaborated the interacting mechanism of internal linkages of BSA, Hb, and dsDNA for solubilizing them without unfolding assisted by glycosidic bonds of glucopyranose units of NaCMC. Magnitudes of regression constants analyse the inner salt bridges, electrostatic dipoles, and hydrogen bonds (HB) to interact with H2O dipoles and NaCMC affecting solubilization of biomolecules (biomols) in areas of biochemical, biophysical, bioengineering, tissue, and genetic engineering. PCPs, UV–Vis, fluorescence, CD, and in-silico study analyse their structurally interacting abilities with NaCMC via respective NHS to be extended to pharmaceutical and cosmetic processes by minimizing quantum energy barrier (QEB) as Newtonian behaviour of structural sensors.

Interfacial properties of cationic and anionic Gemini surfactant mixtures

AbstractThe possibility and the prospect of cationic/anionic (“catanionic”) surfactant mixtures based on sulfonate Gemini surfactant (SGS) and bisquaternary ammonium salt (BQAS) in the field of enhanced oil recovery was investigated. The critical micelle concentration (CMC) of SGS/BQAS surfactant mixtures was 5.0 × 10−6 mol/L, 1–2 orders of magnitude lower than neat BQAS or SGS. A solution of either neat SGS or BQAS, could not reach an ultra‐low interfacial tension (IFT); but 1:1 mol/mol mixtures of SGS/BQAS reduced the IFT to 1.0 × 10−3 mN/m at 100 mg/L. For the studied surfactant concentrations, all mixtures exhibited the lowest IFT when the molar fraction of SGS among the surfactant equaled 0.5, indicating optimal conditions for interfacial activity. The IFT between the 1:1 mol/mol SGS/BQAS mixtures and crude oil decreased and then increased with the NaCl and CaCl2 concentrations. When the total surfactant concentration was above 50 mg/L, the IFT of SGS/BQAS mixtures was below 0.01 mN/m at the studied NaCl concentrations. Adding inorganic salt reduced the charges of hydrophilic head groups, thereby making the interfacial arrangement more compact. At the NaCl concentration was above 40,000 mg/L, surfactant molecules moved from the liquid–liquid interface to the oil phase, thus resulting in low interfacial activity. In addition, inorganic salts decreased the attractive interactions of the SGS/BQAS micelles that form in water, decreasing the apparent hydrodynamic radius (DH, app) of surfactant aggregates. When the total concentration of surfactants was above 50 mg/L, the IFT between the SGS/BQAS mixtures and crude oil decreased first and then increased with time. At different surfactant concentrations, the IFT of the SGS/BQAS mixtures attained the lowest values at different times. A high surfactant concentration helped surfactant molecules diffuse from the water phase to the interfacial layer, rapidly reducing the IFT. In conclusion, the cationic‐anionic Gemini surfactant mixtures exhibit superior interfacial activity, which may promote the application of Gemini surfactant.

Temperature-dependent water retention and bleeding of fresh cement-based materials with VEAs

It is still uncertain whether temperature exerts some influence on the water retention (WR) and bleeding of cement-based materials with viscosity-enhancing admixtures (VEAs). Thus, WR and bleeding of cement-based materials with selected VEAs, such as sodium polyacrylate (PANA), hydroxyethoxy methoxy cellulose (HEMC) and hydroxypropoxy methoxy cellulose (HPMC), were evaluated at 20, 30, 40, 50, and 60 °C, and experiments on the apparent viscosity, total organic carbon (TOC) content, hydrodynamic radius and thermogravimetry were carried out to explore the responsible mechanisms. The results show that VEAs enhance WR and reduce bleeding at room temperature to varying degrees. However, this improvement at higher temperature does not occur as at room temperature (20 °C). The decreased improvements in WR and bleeding at higher temperature are associated with the lowered apparent viscosity, TOC content, hydrodynamic radius and the increased cement hydration. Below 40 °C, the apparent viscosity, adsorption and hydrodynamic radius dominate the bleeding behaviour of mortars with HPMC and HEMC. However, accelerated cement hydration is mainly responsible for the behaviour when the temperature exceeds 40 °C.

Self-assembly behavior and conformation of amphiphilic hemicellulose-graft-fatty acid micelles

In this work, a series of amphiphilic hemicellulose-based grafting polymers are synthesized by homogeneous esterification with various hydrophobic chain fatty acids. With the flexible chain conformation of hemicelluloses, the hemicellulose-graft-fatty acid is self-assembled into hard sphere micelles in aqueous solution through hydrophobic interactions. The resultant micelles show apparent hydrodynamic radius (Rh) varying in the range of 34–57 nm and radius of gyration (Rg) varying from 30 to 44 nm. Moreover, the Rh, Rg, zeta potential and critical micelle concentration (CMC) of the micelles gradually decreases with the increasing hydrophobic chain length. The aggregation number of micelles can be tuned by varying alkyl chain lengths. Taking curcumin (Cur) as a model drug, the hemicellulose micelles were investigated as drug carriers, which exhibit a chain length-controlled drug release behavior. Taken together, structure and property tunable hemicellulose-based micelles were obtained, and showed potential of application in pharmaceutical, food, and cosmetics fields.

Hydrodynamic Radius of Polymer-Coated Nanoparticles Measured by Taylor Dispersion: A Mathematical Model.

This theoretical work addresses the characterization of polymer-coated nanoparticles via the analysis of Taylor dispersion experiments. Our focus is on determining the apparent hydrodynamic radius and the related accuracy bias, which results from polydispersity and optical-absorption-weighted averages. To that end, we construct a statistical model addressing joint distributions of particle core size and ligand surface density, which determine the hydrodynamic radius and optical absorption of such nanoparticles. Our model predicts that a polymer shell that is thick compared with the core radius results in a smaller bias than a thin shell, and the bias may become even negative when ligand surface density is sufficiently high.

Self-Assembly of Exendin-4-Derived Dual Peptide Agonists is Mediated by Acylation and Correlated to the Length of Conjugated Fatty Acyl Chains

Dual glucagon-like peptide-1/glucagon receptor agonists have emerged as promising candidates for the treatment of diabetes and obesity. Issues of degradation sensitivity and rapid renal clearance are addressed, for example, by the conjugation of peptides to fatty acid chains, promoting reversible albumin binding. We use combined dynamic and static light scattering to directly measure the self-assembly of a set of dual peptide agonists based on the exendin-4 structure with varying fatty acid chain lengths in terms of apparent molecular mass and hydrodynamic radius (RS). We use NMR spectroscopy to gain an insight into the molecular architecture of the assembly. We investigate conformational changes of the monomeric subunits resulting from peptide self-assembly and assembly stability as a function of the fatty acid chain length using circular dichroism and fluorescence spectroscopy. Our results demonstrate that self-assembly of the exendin-4-derived dual agonist peptides is essentially driven by hydrophobic interactions involving the conjugated acyl chains. The fatty acid chain length affects assembly equilibria and the assembly stability, although the peptide subunits in the assembly retain a dynamic secondary structure. The assembly architecture is characterized by juxtaposition of the fatty acyl side chains and a hydrophobic cluster of the peptide moiety. This cluster experiences local conformational changes in the assembly compared to the monomeric unit leading to a reduction in solvent exposure. The N-terminal half of the peptide and a C-terminal loop are not in contact with neighboring peptide subunits in the assemblies. Altogether, our study contributes to a thorough understanding of the association characteristics and the tendency toward self-assembly in response to lipidation. This is important not only to achieve the desired bioavailability but also with respect to the physical stability of peptide solutions.

Tannic Acid-Mediated Aggregate Stabilization of Poly(N-vinylpyrrolidone)-b-poly(oligo (ethylene glycol) methyl ether methacrylate) Double Hydrophilic Block Copolymers.

The self-assembly of block copolymers in aqueous solution is an important field in modern polymer science that has been extended to double hydrophilic block copolymers (DHBC) in recent years. In here, a significant improvement of the self-assembly process of DHBC in aqueous solution by utilizing a linear-brush macromolecular architecture is presented. The improved self-assembly behavior of poly(N-vinylpyrrolidone)-b-poly(oligo(ethylene glycol) methyl ether methacrylate) (PVP-b-P(OEGMA)) and its concentration dependency is investigated via dynamic light scattering (DLS) (apparent hydrodynamic radii ≈ 100–120 nm). Moreover, the DHBC assemblies can be non-covalently crosslinked with tannic acid via hydrogen bonding, which leads to the formation of small aggregates as well (apparent hydrodynamic radius ≈ 15 nm). Non-covalent crosslinking improves the self-assembly and stabilizes the aggregates upon dilution, reducing the concentration dependency of aggregate self-assembly. Additionally, the non-covalent aggregates can be disassembled in basic media. The presence of aggregates was studied via cryogenic scanning electron microscopy (cryo-SEM) and DLS before and after non-covalent crosslinking. Furthermore, analytical ultracentrifugation of the formed aggregate structures was performed, clearly showing the existence of polymer assemblies, particularly after non-covalent crosslinking. In summary, we report on the completely hydrophilic self-assembled structures in solution formed from fully biocompatible building entities in water.

Flow-Induced Dispersion Analysis (FIDA) for Protein Quantification and Characterization.

Flow-Induced Dispersion Analysis (FIDA) enables characterization and quantification of proteins under native conditions. FIDA is based on measuring the change in size of a ligand as it selectively interacts with the target protein. The unbound ligand has a relatively small apparent hydrodynamic radius (size), which increase in the presence of the analyte due to binding to the analyte. The Kd of the interaction may be obtained in a titration experiment and the measurement of the apparent ligand size in an unknown sample forms the basis for determining the analyte concentration. The apparent molecular size is measured by Taylor dispersion analysis (TDA) in fused silica capillary capillaries. FIDA is a "ligand-binding" assay and has therefore certain features in common with Enzyme-Linked Immunosorbent Assay (ELISA), Surface Plasmon Resonance (SPR), and Biolayer Interferometry (BLI) based techniques. However, FIDA probes a single in-solution binding event and thus makes assay development straightforward, and the absolute size measurement enables built-in assay quality control. Further, as FIDA does not involve surface chemistries, complications related to nonspecific adsorption of analyte and assay components are minimized enabling direct measurement in, e.g., plasma and serum.

Effect of organic and inorganic salt environment on the complex coacervation of in situ formed protein nanoparticles and DNA

Complex coacervation was noticed between in situ formed protein (a primarily hydrophobic Zein protein with pI = 6.2) nanoparticles (size 80–120 nm) and ds-DNA (a high charge density polyanion), in the ionic liquid (IL) solutions of 1-ethyl-3-methyl imidazolium chloride [C2mim][Cl], and 1-octyl-3-methyl imidazolium chloride [C8mim][Cl], in the studied ionic strength range of I = 10−4 to 6 × 10−1 M, which was extended to strong monovalent 1:1 electrolyte (NaCl) to explore the commonality between the organic and inorganic salt (ionic) environment on coacervation. The salt dependent coacervation profile was monitored from the measured turbidity of the interacting solution, and zeta potential, (ζ) and apparent hydrodynamic radius (Rh) of interpolymer complexes, which depicted the following three discernible interaction regimes common to all the salts: (i) Region-I: I = 0.0001–0.01 M, primary binding, (ii) Region-II, I = 0.01–0.1 M, secondary binding, and (iii) Region-III, I = 0.1–0.6 M, saturation binding. The free-energy and the network density calculations favored preferential coacervation in [C2mim][Cl] samples. Nonetheless, commonality in the overall ionic strength dependent coacervation profiles could still be observed.

Difference in dilute aqueous solution behavior between poly(ethylene glycol) and poly(ethylene oxide)

Static light scattering behavior was examined for poly(ethylene glycol) (PEG) and poly(ethylene oxide) (PEO) of small weight-average molecular weight M w (3 × 103−2 × 104), in methanol and water at 25.0 °C, the former polymer having hydroxy groups at both ends and the latter having a methoxy group at one end and a hydroxy group at the other. It was found that some aggregates of large size are formed in aqueous solutions of the PEO samples with M w = 3.81 × 103 and 7.00 × 103, while all PEG and PEO samples are isolated in methanol solutions, and the PEG samples and the PEO sample of the largest M w (=1.60 × 104) are also isolated even in the aqueous solutions. From the results of dynamic light scattering measurements for the aqueous solution of the PEO sample with M w = 3.81 × 103 at 25.0 °C, there were detected two classes of scatterers having different sizes, i.e., the isolated chains and aggregates, the apparent hydrodynamic radius of the latter being ca. twenty times as large as that of the former. Static light scattering measurements are carried out for poly(ethylene glycol) and poly(ethylene oxide) (PEO) of the weight-average molecular weight M w ranging from 3×103 to 2×104 in methanol and water at 25.0 °C. Some aggregates of large size are found to be formed only in the cases of PEO of M w∼O(103) in aqueous solutions, although for other cases polymer chains are isolated in solutions.

Aggregation and Rheological Behavior of the Lavender Oil-Pluronic P123 Microemulsions in Water-Ethanol Mixed Solvents.

The effect of lavender oil on aggregation characteristics of P123 in aqueous-ethanolic solutions is investigated systematically by DLS, SANS, and rheology. The solubilization capacity of the P123 based formulations toward Lavender oil increased by increasing P123 concentration. The study unveiled the importance of the short chain alcohol-ethanol, as solubilization enhancer. The apparent hydrodynamic radius (Rh) increased significantly with an increase in lavender oil concentration up to maximum oil solubilization capacity of the copolymer at a particular ethanol concentration. DLS measurements on 5, 10, and 15 wt% P123 in the presence of 25% ethanol revealed the presence of large-sized micellar clusters in addition to the oil swollen micelles. The core size (RC), radius of hard sphere (RHS), and aggregation number (N) obtained from SANS profiles showed considerable enhancement with the addition of lavender oil confirming penetration of oil inside the copolymer. Rheological studies showed that viscosity also increased significantly with the addition of lavender oil near the maximum loading limit of the P123 concentration. Quite interestingly, the sol-gel transition temperature displayed a strong dependence on both P123 as well as oil concentration and decreased almost linearly by increasing oil concentration. This study demonstrates the use of a biocompatible and temperature sensitive self-assembled P123 based formulation for lavender oil solubilization that can be beneficial in the cosmetic industry wherein controlled release of fragrances and so forth is demanded.

Steady-shear and viscoelastic properties of cellulose nanofibril\u2013nanoclay dispersions

We have investigated the steady-shear and viscoelastic properties of composite dispersions of cellulose nanofibrils (CNFs) with medium or high charge density and two different nanoclays, viz. rod-like sepiolite or plate-like bentonite. Aqueous dispersions of CNFs with medium charge density displayed significantly lower steady-state viscosity and storage modulus but higher gelation threshold compared with CNFs with high charge density. Dynamic light scattering (DLS) results showed that the apparent hydrodynamic radius of bentonite particles increased when CNFs were added, implying that CNFs adsorbed onto the amphoteric edges of the plate-like bentonite particles. The sepiolite network in CNF–sepiolite dispersions was relatively unaffected by addition of small amounts of CNFs, and DLS showed that the hydrodynamic radius of sepiolite did not change when CNFs were added. Addition of CNFs at concentrations above the gelation threshold resulted in drastic decrease of the steady-shear viscosity of the sepiolite dispersion, suggesting that the sepiolite network disintegrates and the rod-like clay particles are aligned also at low shear rate. The relative change in the rheological properties of the clay-based dispersions was always greater on addition of CNFs with high compared with medium charge density. This study provides insight into how the rheology of CNF–nanoclay dispersions depends on both the nanoclay morphology and the interactions between the nanoclay and nanocellulose particles, being of relevance to processing of nanocellulose–clay composites.

Effect of sodium dodecyl benzene sulfonate to the displacement performance of hyperbranched polymer

Experimental studies were conducted to realize displacement performance effect of anionic surfactant sodium dodecyl benzene sulfonate (SDBS) on hyperbranched poly(AM/AA/AMPS/GA), which was successfully synthesized via free radical polymerization using modified dendritic functional monomer (GA), acrylamide (AM), acrylate (AA), and 2-acrylamido-2-methyl propane sulfonic acid (AMPS). Compared with individual polymer, SP (surfactant polymer) binary systems showed lower apparent viscosity, interfacial tension, and hydrodynamic radius as the result of the electrostatic repulsion between the tail end of hydrophilic polymer branched chain and the head of the surfactant. It was found from abundant static adsorption and dynamic retention tests that the values of static adsorption and dynamics retention of SDBS which is mixed with hyperbranched polymer decrease due to the competitive interaction. However, unlike this phenomenon, SDBS would heighten the dynamic retention value of poly(AM/AA/AMPS/GA), resulting in addition of residual resistance factor. Oil displacement experiment indicated that SP solutions have greater capability of enhance oil recovery than individual polymer under same conditions.

Water soluble poly(styrene sulfonate)-b-poly(vinylidene fluoride)-b-poly(styrene sulfonate) triblock copolymer nanoparticles

Water-soluble PNaSS-b-PVDF-b-PNaSS triblock copolymer.

Effect of mixed micellization on dimensions of 1-butyl-3-methylimidazolium dodecylsulfate micelles in presence of electrolytes

Abstract The association behavior of an amphiphilic ionic liquid 1-butyl-3-methylimidazolium dodecylsulfate ([bmim][DS]) and a non-ionic surfactant Brij30, in the presence and absence of NH4Cl and NaCl, was investigated using DLS, SANS and Rheology. The apparent hydrodynamic radius (Rh) of the mixed micelles increases with increase in mole fraction of the non-ionic component. The variation in micellar size with Brij30 mole fraction is sensitive to the nature and concentration of the two salts. The increase in size of mixed micelles is more pronounced in presence of NH4Cl than NaCl, owing to higher salting out effect of NH4+ ions compared to Na+ ions. The hydrodynamic radius of the mixed mcielles decreases with increase in temperature from 25 °C to 45 °C, due to dehydration of oxyethylene units in Brij30. SANS studies reveal that [bmim][DS] micelles grow significantly with increase in Brij30 mole fraction and the presence of salt facilitates micellar elongation. The zero shear viscosity of mixed micelles in the presence of 0.4 M NH4Cl and NaCl increases with Brij30 mole fraction, the effect being more in presence of the former.

Synthesis of maltopentaose-conjugated surface-active styrenic monomers and their micellar homopolymerization in water

Maltopentaose (Mal5)-conjugated surface-active styrenic monomers 1a, 1b, and 1c are described, which contain hydrophobic spacers, such as C1, C5, and C7 alkylene chains, respectively. The glycomonomers 1a-c were synthesized by the direct β-N-glycosyl reaction of styrene derivatives with aminoalkyl groups 4a-c onto Mal5 in dry methanol, followed by the N-acetylation with acetic anhydride. The self-assembling properties for the aqueous solutions of 1a-c were characterized by surface tension measurements and light scattering experiments, providing the physicochemical parameters for the formed 1a-c micelles including the critical micelle concentration, apparent hydrodynamic radius (Rh,app), and weight average aggregation number (Nagg). The transmission electron microscope observations revealed the most important result in this study that 1a produced loose spherical micelles with the number average diameter (dn) of 26 nm, while both 1b and 1c formed worm-like micelles with the polymerizable core and the Mal5 shell, whose number average contour lengths (lns) were 130 nm and 68 nm, respectively. The radical homopolymerizations of 1a-c in water provided a substantial result in this study that 1b and 1c, that is, the glycomonomers forming the worm-like micelles, showed a very high homopolymerizability in water. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1671–1679

Characterization of engineered alumina nanofibers and their colloidal properties in water

Aluminum oxide nanofibers having different fiber diameters were characterized to determine if and how the fiber diameter affects their colloidal behavior and solubility in water. The measurements provide initial data on the behavior of alumina nanofibers in aqueous systems. Three different aluminum oxide materials with average fiber diameters ranging from a few nanometers to a few hundred nanometers were acquired from ANF Technology (Nafen™), MemPro Materials, and Pardam Nanotechnology. The morphology, dimensions, chemical composition, and surface properties of each material were measured using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, and N2-BET surface area analysis. Properties measured for aqueous suspensions of the fibers included electrophoretic mobility, point of zero charge, apparent hydrodynamic radius via dynamic light scattering, and solubility. TEM images were used to determine the size distribution of the fiber diameter, and the smooth, non-porous, non-tubular structure of the materials. Fiber diameters were 5–10 nm for Nafen™, 90–175 nm for MemPro, and 150–600 nm for Pardam. SEM showed that samples of the dry materials consisted of long (micron sized) fibers having these diameters. Specific surface area ranged from 2.7 m2/g for the largest diameter Pardam fibers to 136 m2/g for the smallest diameter Nafen™ fibers. The pH of the point of zero charge for the three materials ranged from 5.0 for Pardam to 8.5 for Nafen™ in 10 mM NaCl. Dynamic light scattering revealed that the fibers readily aggregate in both deionized water and solutions of high ionic strength. Fiber solubility ranged from a dissolved aluminum concentration of 23–83 μg/L for pH from 6.67 to 8.23. The observed solubilities were similar to those calculated from thermodynamic data for corundum (α-Al2O3) and boehmite (γ-AlO(OH)), phases that were observed by XRD in the aged materials.