Shear thickening behavior of dilute poly(diallyl dimethyl ammonium chloride) aqueous solutions

Influence of the injection of densified polymer suspension on the efficiency of DNAPL displacement in contaminated saturated soils

Nowadays the remediation of DNAPL contaminated zones near groundwater has gained great prominence in environmental fields due to the high importance of water resources. In this work, we suggest injecting a densified polymer suspension by adding barite particles to displace DNAPL. To evaluate the efficiency of the densification of polymer suspensions on the displacement of DNAPL, various densities of barite-polymer suspension; lower, equal, and higher than the density of DNAPL were prepared and their rheological behavior was analyzed. Then flow experiments were performed using a decimetric-scale 2D tank. The displacement procedure was monitored with an imaging technique and the production and injection process data were recorded by mass balance interpretation. It was shown that the densification of the polymer suspension could improve the displacement efficiency of DNAPL up to four times. The clogging behavior of barite-polymer suspension was assessed in a 1D column. Generalized Darcy's law and the continuity equation were used to numerically simulate the experimental two-phase flow. To take into account the clogging behavior of the suspension, the transport equation of diluted species was implemented into the model. The simulation results show that the model can properly predicts the experimental consequences.

Augmented polyhydrazone formation in water by template-assisted polymerization using dual-purpose supramolecular templates

Template-assisted polymerization using donor–acceptor supramolecular templates results in higher M_w and M_n values, decreased critical hydrogelation concentrations, and increased gel recovery velocity following shear-induced breakdown.

Polyethylene Oxide (PEO) Molecular Weight Effects on Abuse-Deterrent Properties of Matrix Tablets

While polyethylene oxide (PEO)-based matrix tablets are frequently used as abuse-deterrent dosage forms, there is limited information available regarding how the selection of formulation components and manufacturing processes affect the resulting abuse-deterrent properties. The objective of the current study was to evaluate the effects of formulation and process variables on the abuse-deterrent features of PEO-containing tablets. Directly compressed tablets were prepared using three different PEO molecular weights (100,000; 900,000; and 5,000,000). As anticipated, sintering/thermal treatment above the melting point of PEO was crucial to impart crush-resistant features (tablet hardness > 500 N). In addition to the sintering temperature, the weight fraction of PEO in the tablets affected their mechanical strength, and at least 50% w/w PEO was required to impart the desired crush-resistant features. In addition, the formulation and process variables also impacted syringeability and injectability of the PEO gels formed when the tablets were hydrated to simulate attempted drug extraction. High molecular weight PEO (900,000 and 5,000,000) produced gels more resistant to syringeability and injectability compared to low molecular weight PEO (100,000). Sintering above the polymer melting point decreased PEO crystallinity after cooling, and longer sintering times resulted in PEO degradation producing lower viscosity gels with reduced resistance to syringeability and injectability. Although sintering above the melting point of PEO imparts optimal mechanical strength to the tablets, prolonged sintering durations negatively impact polymer stability and alter the resulting abuse-deterrent features of the PEO-based tablet formulations.

Viscosity Behavior of P(DAC-AM) with Serial Cationicity and Intrinsic Viscosity in Inorganic Salt Solutions

The poly(acryloyloxyethyl trimethyl ammonium chloride-co-acrylamide), P(DAC-AM), is a kind of cationic polyelectrolyte usually applied in a solution form, and its performance is affected by its structure and the environment where it is used. In particular, its viscosity properties in salt solutions are directly related to its efficacy in various applications, and the performance is one of the most important solution properties. Therefore, in this paper, the effects of the salt concentration and valence of seven kinds of inorganic salts, NaCl, LiCl, KCl, MgCl₂, AlCl₃, Na₂SO₄, and Na₃PO₄, on the values of apparent viscosity (η_a) of P(DAC-AM) samples with cationicity of 10%, 50%, and 90%, and intrinsic viscosity ([η]) of 5, 10, and 15 dL/g were investigated. The η_a was determined using a rotational viscometer. The interaction mechanism between the polymers and salt ions was also investigated. The results showed that depending on the salt concentration, the η_a firstly decreased sharply to the inflection point which indicated the minimum volume of the molecule shrinking, and then either maintained the value unchanged or increased. The salt concentration corresponding to the inflection point decreased with the increase of the salt ion valence but with the reduction of the cationicity of the polymer. The η_a at the inflection point increased as the [η] of the polymer grew. This indicated that the salt concentration and the salt ion valence had a notable impact on the stretch of the cationic polymer molecule in the salt solutions. It was discovered that the phenomenon of the increase of the η_a of P(DAC-AM) samples in the multivalent salt solutions after the inflection point was caused by not only the increase of the η_a of the complexes formed from the pure salts, but also the viscosity resistance of the charge and volume between the polymer molecules and salt ions, as well as the complexes themselves. The linear relationship between the increased η_a and the salt concentration, representing the interaction both among the complexes themselves and between the polymer and complexes, was obtained. Furthermore, the interaction model between the salt ions and P(DAC-AM) molecules in a wide range of salt concentrations was illustrated.

Chromatographic NMR with size exclusion chromatography stationary phases

Chromatographic NMR describes the use of stationary phases or solvent additives, such as polymers, to modify the diffusion properties of analyte molecules and thereby improve the observed resolution in the diffusion domain. This paper demonstrates similar ideas using size exclusion chromatographic media and characterises the changes in the observed diffusion coefficient using a series of polymer molecular weight reference standards of known polydispersity. The results are interpreted in terms of a simple description of the size exclusion phenomena.

Peculiarities of polyelectrolyte multilayer assembly on patterned surfaces

The layer-by-layer assembly of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate) is studied on templates with imprinted arrays of microwells ranging from 2 to 25 μm and different aspect ratios. The thickness and microstructure of polyelectrolyte multilayers (PEMs) are measured using scanning electron microscopy. At 0.2 M ionic strength, the PEM film evenly coats the template both inside and outside the microwells. If the film is thinner than the critical value of about 400 nm, PEM microstructures collapse upon dissolving the template. Euler's model of critical stress is used to describe the collapse. At 2 M ionic strength, a substantially thinner PEM film is assembled inside the 25 μm wells than outside. If the well diameter is reduced to 7 and 2 μm, a much thicker PEM film is formed inside the microwells. These observations have been attributed to the changing of polyelectrolyte conformation in the solutions.

Rheological characterization of poly(ethylene oxide) solutions of different molecular weights

The rheological properties of aqueous solutions of poly(ethylene oxide) (PEO) of different molecular weights (1x10(5), 4x10(5), 1x10(6) and 4x10(6) g mol(-1)) and concentrations were investigated using shear viscosity and dynamic rheological measurements. It was found that the aqueous solutions of PEO do not exhibit a yield stress and that, above a critical shear rate, all PEO solutions exhibit shear-thinning behavior, well described by the Cross model, except for the solutions made by the lowest molecular weight (1x10(5) g mol(-1)) which were almost Newtonian. The parameters of the Cross model, namely the zero-shear rate viscosity and reciprocal of the time constant, allowed the determination of the critical concentrations c(*) and c(**) (respectively, the transition to semi-dilute network solution and concentrated solution). At concentrations higher than c(**) and below a critical shear rate, solutions made of PEO of high molecular weight exhibited a clearly shear-thickening behavior at very low shear rates. In addition, the dynamic tests showed that PEO solutions exhibit concentration-dependent viscoelastic properties, with a dominant viscous behavior at PEO concentrations lower than c(**) and a dominant elastic behavior at PEO concentrations greater than c(**).

Surface-enhanced Raman scattering substrates fabricated using electroless plating on polymer-templated nanostructures

Surface-enhanced Raman scattering (SERS) has great potential as an analytical technique based on the unique molecular signatures presented even by structurally similar analyte species and the minimal interference of scattering from water when sampling in aqueous environments. Unfortunately, analytical SERS applications have been restricted on the basis of limitations in substrate design. Herein, we present a simple SERS substrate that exploits electroless deposition onto a nanoparticle-seeded polymer scaffold that can be fabricated quickly and without specialized equipment. The polymer-templated nanostructures have stable enhancement factors that are comparable to the traditional silver film over nanospheres (AgFON) substrate, broad localized surface plasmon resonance spectra that allow various Raman excitation wavelengths to be utilized, and tolerance for both aqueous and organic environments, even after 5 day exposure. These polymer-templated nanostructures have an advantage over the AgFON substrate based on the ease of fabrication; specifically, the ability to generate fresh SERS substrates outside the laboratory environment will facilitate the application of SERS to new analytical spectroscopy applications.