Chemical degradation of guar gum solutions via the addition of a strong oxidant is a common process step in hydraulic fracturing. Unfortunately, this degradation step leads to the formation of an ...insoluble precipitate which clogs the porous rock formation, reducing efficiency, reducing oil recovery potential, and increasing energy costs. The chemical composition, particle size, and molecular weight distributions of the oxidatively degraded guar (“broken guar”) are largely unknown, making it difficult to develop mitigation strategies. In this work, broken guar gum solutions are systematically analyzed to understand the origin of the observed residue. Our results indicate that cellulose fibers and proteins, rather than galactomannan oligomers, are the two major components (>50%) of the solid residue (the water‐insoluble fraction of broken guar). This finding suggests that removal of the cellulose fiber and proteins from the guar source material may be a potential residue mitigation strategy. Separately, we provide evidence for a potential second mitigation strategy employing chemical additives to reduce aggregation of the insoluble species, effectively reducing their potential to cause formation damage.
Aqueous solutions of guar gum were cleaved by ammonium persulfate and analyzed by monad and protein analyses. Surprisingly, insoluble cellulose fibers and proteins, rather than galactomannan oligomers, were the major components of the water‐insoluble fraction.
Low aqueous solubility of active pharmaceutical ingredients (APIs) is an enduring problem in pharmaceutical development, and it is becoming increasingly prevalent among new drug candidates. It is ...estimated that about 40% of drugs in the development pipeline and approximately 60% of the drugs coming directly from discovery suffer from poor aqueous solubility and slow dissolution, thereby reducing their bioavailability and efficacy and thus preventing their commercialization. It is well known that utilizing the amorphous form of a drug can be a useful approach to improve the dissolution rate and solubility of poorly water-soluble APIs. Amorphous compounds are thermodynamically unstable, but they can be stabilized by combining them with a carrier polymer (excipient) to form a solid dispersion. High-throughput Raman spectroscopy was used in this study to identify excipients that promote formation and stabilization of the amorphous drug form in solid dispersions. Four model APIs were used as poorly soluble drug candidates: ketoprofen, danazol, griseofulvin, and probucol. The Raman signals of excipients were generally negligible, and therefore Raman bands from the drugs were used with minimal spectral pre-processing. By comparing Raman spectra collected from the APIs in the crystalline and molten state, appropriate spectral features and regions were identified for the development of semi-quantitative methods to determine the amorphous content for each API. It is demonstrated that methods based on peak intensity ratio, peak width, peak distance, and classical least squares can all be effective methods for the screening of excipients. Interesting excipient-dependent phase transformation behavior was also observed for probucol.
We report the synthesis and characterization of catechol-functionalized film-forming latexes that display excellent adhesion to low-surface-energy polyolefin-based substrates. The aromatic 1,2-diol ...functional group in catechol derivatives is believed to be responsible for enhancing the adhesion of a variety of polymers to a range of substrates. Here, we describe a postpolymerization modification approach to the design of emulsion polymers with catechol-functionalized side chains. A series of analogous small-molecule reactions, together with latex characterization by infrared (IR) spectroscopy and liquid chromatography (LC) methods, provides evidence for polymer functionalization. Films prepared from catechol-containing latexes displayed remarkable adhesion to challenging, commercially-available thermoplastic polyolefin (TPO) (as determined by a standard ASTM cross-hatch method). We provide evidence that covalent bonding and the unique catechol structure are required to promote adhesion. The catechol-functionalized emulsion polymers reported here represent a new class of functional latex, and this postpolymerization modification approach will present further opportunities to improve, modulate, and control the adhesion of water-borne coatings to a variety of polyolefin-based substrates.
Size-exclusion chromatography (SEC), coupled with differential viscometry detection (SEC/DV), is applied to the dilute suspension characterization of solvent-swollen cross-linked polymeric ...nanoparticles (PNPs). Cross-linked, unimolecular polymeric nanoparticles in the 5–50 nm weight-average diameter (d w) range were prepared by batch and semibatch microemulsion polymerization techniques and isolated. SEC and SEC/DV characterization techniques yield, based on the principle of universal calibration, a wealth of information regarding the structural attributes of PNPs, including apparent and absolute molecular weight distributions, apparent and absolute molecular weight averages, peak and weight-average particle diameters, particle size distributions in both the solvent-swollen and solvent-free states, particle conformation (shape), and an estimate of the volumetric swell factor. These structural parameters are critical to understanding PNP performance, and all are obtained in a single rapid chromatographic experiment, when conducted under conditions where universal calibration applies. Particle sizes determined under such conditions are in excellent agreement with those obtained by dynamic light scattering, transmission electron microscopy, hydrodynamic chromatography, and SEC/static light scattering (SEC/SLS). In addition, Mark–Houwink exponents of approximately zero were found across the molecular weight and size distribution of many of these tightly cross-linked PNPs, which is consistent with a spherical particle conformation in these dilute suspensions. The SEC/DV methods are especially valuable to characterize the diameter, volume swell factor, and suspension conformation of small (4–5 nm d w) PNPs.
Particulate bis1-(hydroxy-κO)-2(1H)-pyridinethionato-κS
2
-(T-4)-zinc (zinc pyrithione; ZPT) in the diameter range 0.5-0.7 µm is a US FDA-approved anti-dandruff active widely used in anti-dandruff ...shampoos. A nanoparticulate form of ZPT is expected to exhibit a higher activity, be distributed more effectively on the scalp, require less thickening agent in the shampoo formulation to ensure its stability against settling than the standard form of ZPT, and would enable clear anti-dandruff shampoo formulations. We demonstrate, for the first time, that a green, mechanochemical nanoparticle synthesis process can be used to prepare nanoparticulate ZPT from zinc chloride and sodium pyrithione monohydrate. Both a Reeves attrition mill and a Retsch MixerMill were found to be effective tools for delivering the mechanical energy needed for the conversion. The infrared spectra and X-ray powder diffraction patterns for the products correspond to those for the known desired material. Transmission electron microscopic analysis indicates that ZPT nanoparticles with primary particle diameters in the range of 20-200 nm (mean diameters of 65-100 nm) can be obtained via this method.
Cationic conditioning polymers have a role as deposition aids for depositing benefit agents such as silicone polymers and are used in shampoo formulations to provide improved combing properties, ...feel, and look. The objective of this work was to develop synthetic high-performance polymeric conditioning agents that exhibit conditioning performance as good as, or better than, the current commercially available polymers. We describe the application of high throughput methods to identify high-performance synthetic hair-conditioning polymers through using high throughput combinatorial methods for polymer synthesis and screening to prepare several hundred cationic polymer candidates. Shampoo formulations were then formulated with these polymers; hair tresses were treated with these formulations and tested
a parallel automated wet combing method. Three high-performing polymer candidates were selected for further evaluation, prepared on a larger scale and evaluated
a panel study. A (
-acrylamidopropyl)trimethylammonium chloride-vinyl monomer-based cationic copolymer is shown to exhibit hair conditioning efficiency equal to or greater than that of a high-performance cellulose ether-based polymer, SOFTCAT™ SL-5 (Polyquaternium-67) in a shampoo formulation.
A disodium 1,2-ethanediol bis(hydrogen sulfate) salt, NaO3SOCH2CH2OSO3Na, has been synthesized and anchored onto zirconium hydroxide to produce a high concentration of solid dual acid sites. The ...reaction of HCON(CH3)2·SO3, (CH2OH)2, and NaOH produced a stable NaO3SOCH2CH2OSO3Na precursor in 40% yield. The NaO3SOCH2CH2OSO3Na salt was exchanged with NH4 + using an NH4−R resin followed by impregnation of a zirconium hydroxide slurry, yielding −O3SOCH2CH2OSO3−2- anchored on Zr(OH)4. The characterization of the samples included high-resolution X-ray photoelectron, near-infrared diffuse reflectance, 1H NMR, and 13C magic angle spinning NMR spectroscopies. The results provided evidence of a μ2-CH2CH2− ligand bridged between two −OSO3− groups in the precursor and the anchored precursor. The ethyl bridge was removed upon calcination at 500 °C to yield surface-grafted acid groups on zirconia. This material had a surface area of 97 m2 g-1 and an acid-exchange capacity of 0.70 mequiv of H+/g, corresponding to 7.2 μmol acid sites/m2, which was about 50% higher than that of sulfated zirconia prepared by standard methods of impregnation by sulfuric acid or ammonium sulfate.
Microemulsions are thermodynamically stable, fluid, optically clear dispersions of two immiscible liquids. Recent interest in microemulsion systems has resulted from their utility in a broad range of ...applications including enhanced oil recovery, consumer and pharmaceutical formulations, nanoparticle synthesis, and chemical reaction media. However, the high levels typically required to ensure complete microemulsification and formulation stability often result in unacceptably high residue, contaminant levels, and formulation cost. One way to reduce surfactant requirements in microemulsion systems is through the use of efficient surfactants and interfacially active cosurfactants. We have explored and developed microemulsion systems based on efficient anionic surfactants and glycol ether cosurfactants that are stable to temperature and compositional changes and yet employ low levels of non‐volatile surfactants. These microemulsion systems are finding utility in a range of applications, including consumer and industrial cleaning formulations, chemical reaction media, polymerization, and active ingredient delivery.
Robust microemulsions with low surfactant levels are desirable in order to reduce residue, contaminant levels, and formulation cost (see Figure for pseudo‐ternary phase diagram). This is achieved here through the use of efficient anionic surfactants, interfacially active glycol ether cosurfactants, and appropriate formulation conditions. Chemical reaction media and cleaning formulations are some of the applications of these systems.
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