Polymer Conformance Control Research Articles

Electroresponsive Weak Polyelectrolyte Brushes

We explored the effect of an applied electric field on the molecular conformation of two weak polyelectrolytes grafted on gold electrodes─poly(acrylic acid) and the weak polybase poly(2-(dimethylamino)ethyl methacrylate)─by combining a quartz crystal microbalance with an electrochemical setup. Our results indicate that different mechanisms influence the response of weak polyelectrolytes to an externally applied potential difference, including electrochemical modification of the local pH by oxygen reduction and the electrostatic interaction between the metallic electrode and the charged monomers and ions in solution. Our results evidence that fine control of polymer conformation can be readily obtained at low applied potentials, opening pathways for precise, localized control of surface properties. However, these applications require considering the history-dependent behavior of polyelectrolyte brushes, hysteresis in the response, and the influence of electrochemical reactions driven by potential changes.

Production performance by polymer conformance control in ultra-low permeability heterogeneous sandstone reservoirs produced under their natural energy

For ultra-low permeability and highly heterogeneous sandstone reservoirs, fluid channeling along the high permeability layer leads to a rapid decrease of reservoir pressure coupled with very low sweep efficiency. As an effective conformance control technology, advanced polymer injection can enhance oil production from ultra-low permeability heterogeneous sandstone reservoirs, not only through conformance control but also through increasing reservoir energy. In order to simulate the reservoir energy storage capacity during the polymer injection stage as well as accurately control the energy release rate during the production stage, a novel experimental setup is assessed in this study. Partially hydrolyzed polyacrylamide (HPAM) is used as the polymer conformance control solution. Artificial heterogeneous sandstone cores are used to perform a series of polymer conformance control followed by production under the natural energy of the model reservoir. The effect of polymer injection volume and its concentration on polymer retention and plugging ability are investigated. Without polymer injection, the initial volume of produced liquid is large, however rapidly declines leading to a poor overall oil recovery. This trend accurately captures field performance. Upon advanced polymer injection, although the initial volume of produced liquid relatively decreased, the decline in the rate of liquid production decreases. The reservoir pressure in the later stages of production could still be maintained at a relatively higher level. Subsequently, the production period is prolonged, leading to a significant increase in oil recovery. The increase in the polymer injection volume or polymer concentration delayed polymer evolution from the reservoir, suggesting enhanced polymer plugging ability. Optimal polymer volume of 0.3–0.6 PV at its optimal concentration of 3000 mg/L corresponding to highest oil recovery is attained at the reservoir conditions. In this study, advanced polymer injection is proved to be a feasible technology to significantly improve the sweep efficiency in ultra-low permeability heterogeneous sandstone reservoirs. By controlling the appropriate polymer injection volume and its concentration, the highest recovery of a certain reservoir can be reached. For the oilfield engineers, by virtue of its ability to faithfully capture field trends, the proposed experimental setup may offer a reliable method to determine the optimal polymer injection volume and concentration for given reservoir conditions and characteristics.

Noncovalent Close Contacts in Fluorinated Thiophene–Phenylene–Thiophene Conjugated Units: Understanding the Nature and Dominance of O···H versus S···F and O···F Interactions with Respect to the Control of Polymer Conformation

Using a simple π-conjugated trimer, EDOT–phenylene–EDOT (EDOT = 3,4-ethylenedioxythiophene), we evaluate the effect that fluorine substituents have upon changes in conformation, conjugation, and ox...

Exploring side-chain length effect on β-phase of polyfluorene derivatives in electrospinning and their optical behavior

Unique coplanar β-conformation of polyfluorene, endowed with long effective conjugated length, is promising to form ordered and oriented structures that can result in improved carrier mobility, polarization emission and excellent spectral stability. Herein, a series of polydiarylfluorenes of different side-chains (PHDPF, PODPF or PNDPF) and poly (9-vinylcarbazole) composite nanofibers were prepared via electrospinning approach. It is observed that β-phase can be obtained in PODPF electrospun nanofibers whereas absent in those of PHDPF and PNDPF systems. It can be demonstrated that the optimal chain length for polydiarylfluorenes to β-conformation is an octyl side chain in electrospinning. In contrast with the electrospun nanofibers, there was no β-phase in the corresponding spin-coated film. For the β-phase electrospun nanofibers, the fluorescence quenching sensitivity on 2, 4-dinitrotoluene (DNT) vapor was obviously higher than that of amorphous electrospun nanofibers and spin-coated film, respectively. Synergistic molecular design and electrospun processing may offer a fascinating strategy for the control of polymer conformation to the adjustment of nano and micro optical devices such as organic fluorescence sensors, lasers and light-emitting diodes.

The importance of solvent quality on the modification of conjugated polymer conformation and thermodynamics with illumination.

Device efficiency in key organic electronic devices such as organic photovoltaics, field transistors, and light emitting diodes has long been known to be closely tied to the conformation of the conjugated polymer chains which make up the active layers. Our previous results show that light exposure can have a profound effect on the structure and assembly of these optoelectronic materials in solution. In order to advance our understanding of the role which solvent quality plays in this phenomenon, we have further studied the modulation of these illumination dependent structural changes on the key benchmark conjugated polymers P3HT and MEH-PPV as a function of solvent quality over a wide range of polymer solubilities. Analysis of this data indicates that use of poorer conjugated polymer solvents ultimately results in larger absolute alterations to polymer conformation, denoting the crucial role which solution thermodynamics plays in this generic effect. This discovery opens the door to controlling final device morphology through careful manipulation of solvent composition during solution based device casting techniques, moving our efforts closer to the development of a powerful, non-destructive, and tunable method for light-driven control of polymer conformation in novel light-responsive organic materials.

Transportation characteristics of HPAM solution in the micro-fractures

ABSTRACTIn order to improve the success rate of practical application of an organic polymer conformance control agent in a fractured low permeability reservoir, the transportation characteristics of hydrolyzed polyacrylamide (HPAM) solution in micro-fracture is systematically studied by displacement experiments using the visual model and fractured cores. The results are as follows: (1)There is no threshold pressure for HPAM solution transportation in micro-fracture, and its flow is linear at a certain range of flow rate. (2) There is an appropriate corresponding range between the viscosity of HPAM solution and fracture permeability, which can provide guidance for screening out the appropriate molecular weight or concentration to obey the permeability. (3)Flow resistance of HPAM solution in the micro-fracture is lower than that in porous media at the same water phase permeability, but the difference degree of flow resistance is reduced with the increase of permeability. (4)When the aperture of the lower permeability fractured core in the parallel combination is high, the shunt flow volume of HPAM solution is linear. When the aperture is low, the shunt flow volume is nonlinear. The experimental results can provide important guidance for optimization and application of the polymer conformance control agent in a fractured low permeability reservoir.

The Development and Optimization of a Polymer Conformance Control Technology in Mature Reservoirs: Laboratory Experiments vs. Field Scale Simulation

This article presents a successful investigation of polymer gel behavior from laboratory experiments to full field scale simulation. First, a series of laboratory experiments are conducted to achieve a deep understanding of polymer gel behavior. The results show that the polymer viscosity, gelation time, and gel strength strongly depend on the reservoir temperature, polymer type, polymer concentration, cross-linker concentration, pH, and salt concentration, which are the keys of a polymer conformance control process. According to the laboratory experiments, polymer gel flooding is applied for the White Tiger field, which is the biggest oil field in Viet Nam. The polymer gel treatment is simulated in the full field scale and the results indicate that it is an excellent candidate for conformance control. Water production decreases from 4,800 m3/d to slightly less than 2,000 m3/d, while a significant increase in oil production has been achieved from unswept zones, which is a really successful evidence of the polymer conformance control technology in heterogeneous reservoirs.

Molecular Sieving on the Surface of a Protein Provides Protection Without Loss of Activity

AbstractTethering polymers to surfaces represents the cornerstone of a wide range of applications, including the stabilization of colloids/biomolecules and the preparation of functional coatings. Unfortunately, despite the prevalence of protein‐tethered polymers in the pharmaceutical sector, the analysis of such polymer monolayers on a molecular level is difficult. In this work, simple 1H NMR spectroscopy and the catalytic properties of α‐chymotrypsin are used to analyze the conformational/permeability properties of protein‐bound monolayers of poly(oligoethyleneglycol monomethylether methacrylate) (pOEGMA), a biocompatible comb‐polymer of interest in the biomedical field. By analyzing >100 distinct conjugates of α‐chymotrypsin and pOEGMA, a detailed picture of the behavior of pOEGMA on the surface of a protein was obtained. Remarkably, control of polymer conformation and inter‐penetration produced a thus far overlooked molecular sieving effect. The application of this effect for the “smart” PEGylation of proteins is portrayed, from which insight is provided for the design of other therapeutic bioconjugates and functional coatings with selective permeability properties.

Site-specific polymer-streptavidin bioconjugate for pH-controlled binding and triggered release of biotin.

Low molecular weight copolymers of acrylic acid (AAc) and N-isopropylacrylamide (NIPAAm) have been synthesized with reactive OH groups at one end, using a chain transfer polymerization technique. The copolymer displays both pH and temperature sensitivity over a wide and useful range of pHs and temperatures, which permits both pH and temperature control of polymer conformation. This copolymer has been conjugated to a specific cysteine thiol site inserted by genetic engineering near the recognition site of streptavidin (SAv). In this paper, we demonstrate that this bioconjugate can provide pH control of biotin binding to and triggered release from the mutant SAv. These actions are relevant to affinity separations, biosensors, diagnostics, enzyme processes, and targeted delivery of drugs or chemical agents, labels, and other signals.

Controlling polymer shape through the self-assembly of dendritic side-groups

The chain conformation of polymers plays an important role in controlling their phase behaviour and associated material properties. In the case of flexible polymers, conformation is controlled by the degree of polymerization (DP), with low-DP polymers having extended polymer chains and high-DP polymers adopting random-coil conformations in solution and the bulk amorphous state1, and folded conformations in the crystalline phase2. Exceptions to this general rule are polymers that contain structurally rigid building blocks, or that are subjected to directional shear forces during solidification. The backbones of semi-flexible and rigid rod-like polymers, for example, are always extended in liquid crystalline and crystalline phases3,4,5, and gel-spun flexible polymers form extended-chain crystals2. Here we report a general strategy for the rational control of polymer conformation through the self-assembly of quasi-equivalent monodendritic (branched) side-groups attached to flexible backbones. At low DPs, the conical monodendrons assemble to produce a spherical polymer with random-coil backbone conformation. On increasing the DP, the self-assembly pattern of the monodendritic units changes to give cylindrical polymers with extended backbones. This correlation between polymer conformation and DP is opposite to that seen in most synthetic and natural macromolecules. We anticipate that our strategy will provide new approaches for the rational design of organized supramolecular materials6,7,8,9 in areas such as nanotechnology, functional films and fibres, molecular devices, and membranes, expanding the synthetic and technological uses of dendritic building blocks7,10,11,12,13,14,15.