The role of pH, ionic strength and monomer concentration on the terpolymerization of 2-acrylamido-2-methylpropane sulfonic acid, acrylamide and acrylic acid

Realizing the Efficient Dissolution of Drag Reducer upon pH-Induced Demulsification of Inverse Polymer Emulsion

The increasing exploitation of fossil resources needs to shift people's attention to developing unconventional reservoir resources. Polyacrylamide-based emulsion drag reducers can effectively reduce the turbulence of fracturing fluid and improve oil recovery, but their release effect is poor, which limits their practical application. Here, we constructed a pH-responsive inverse polymer emulsion of poly(acrylamide-2-acrylamido-2-methylpropanesulfonic acid). Interestingly, HOA/Tween 80 exhibits remarkable pH-responsive behavior, which enables the monomer emulsion to change the type of emulsion under pH stimulation. Our results propose that the P(AM-AMPS) polymer emulsion is eluted with the same aqueous phase as the W/O P(AM-AMPS) polymer emulsion, thereby achieving the effect of drag reduction. P(AM-AMPS) can be rapidly released from the inverse polymer emulsion within 70 s upon pH stimulation, the drag reduction rate of which was 60.4%. Obviously, the inverse polymer emulsion prepared by a pH-responsive surfactant not only has good stability but also can achieve rapid release of the polymer upon pH stimulation, which supplies an interesting indication to explain why a balance exists between the stability of the emulsion and release of P(AM-AMPS).

Synthesis and characterization of a smart polymer-coated core–shell MnFe2O4@ organometallic framework for targeted drug delivery

Scientists are currently working to develop more effective and less harmful methods of delivering drugs to tissue. One method is to use a special type of carrier to help the drug get to the right place in the body. In this study, an organometallic framework nanocarrier with the formula IRMOF-3 [Zn4O(NH2-BDC)3] was successfully prepared, containing magnetic nanoparticles of manganese ferrite (MnFe2O4) and the drug doxorubicin encapsulated in a pH- and temperature-sensitive smart polymer of poly-N-isopropylacrylamide. Doxorubicin, an anticancer drug, was loaded into the pores of a magnetic organometallic framework and modified with the smart polymer poly(N-isopropylacrylamide-co-AA), which has a lower critical solution temperature (LCST) of less than 38 °C. The synthesis of magnetic nanoparticles and magnetic organometallic frameworks encapsulated in smart polymer was investigated using various analytical techniques such as Fourier transform infrared spectrometer, thermal stability analysis, BET, and VSM. The particles in the synthesized nanocarrier are uniform in size, have high magnetic properties, and are thermally stable. The effective surface area is 7.26 m2/g, and the pore volume is 166.394 m. The drug carrier has the ability to load up to 78% of the drug into the solution. The highest drug release was observed when the pH was 5 and the temperature was higher than the LCST. 71% of cancer cells were destroyed by the drug carrier in the culture medium. This nanosystem, designed with more drug retention, reduced side effects and controlled release in different conditions, is suitable as a drug delivery system.

Triblock Superabsorbent Polymer Nanocomposites with Enhanced Water Retention Capacities and Rheological Characteristics

Superabsorbent polymers (SAPs) are useful polymers in a wide range of application fields ranging from the hygiene industry to construction and agriculture. As versatility and high water absorption capacity are their important merits, SAPs usually suffer from low water retention capacity (fast release) and weak mechanical properties. To address these drawbacks, a set of new superabsorbent polymer-Halloysite nanotube (HNT) nanocomposites was synthesized via free radical polymerization of acrylamide, 2-acrylamido-2-methylpropane-1-sulfonic acid, and acrylic acid in the presence of vinyltrimethoxysilane (VTMS) as the crosslinker. FTIR and TGA characterizations confirm the polymerization of SAP and successful incorporation of HNTs into the SAP polymer matrix. The effect of the HNT nanofiller amount in the nanocomposite polymer matrix was investigated with swelling-release performance tests, crosslink density calculations, and rheology measurements. It was found that equilibrium swelling ratios are correlated and therefore can be tuned via the crosslink densities of nanocomposites, while water retention capacities are governed by storage moduli. A maximum swelling of 537 g/g was observed when 5 wt % HNT was incorporated, in which the crosslink density is the lowest. Among the SAP nanocomposites prepared, the highest storage modulus was observed when 1 wt % of nanofiller was incorporated, which coincides with the nanocomposite with the longest water retention. The water release duration of SAPs was prolonged up to 27 days with 1% HNT addition in parallel with the achieved maximum storage modulus. Finally, three different incorporation mechanisms of the HNT nanofiller into the SAP nanocomposite structure were proposed and confirmed with rheology measurements. This study provides a rapid synthesis method for SAP nanocomposites with enhanced water retention capacities and explains the relationship between swelling and crosslink density and water retention and mechanical properties of SAP nanocomposites.

Liquid Crystalline Copolymers Containing Sulfonic and Light-Responsive Groups: From Molecular Design to Conductivity

In the search for novel smart multifunctional liquid crystalline materials, we report the synthesis, thermal and structural characterisation, and the conductivity, of a set of new block and statistical copolymers, containing light-responsive mesogenic groups (MeOAzB), polar sulfonic acids (AMPS), and methyl(methacrylate) groups (MMA). By using a cascade of reversible addition-fragmentation chain polymerisations, RAFT, we have tailored different side-chain polymeric structures by controlling monomer composition (MeOAzB/AMPS/MMA) and configuration. We have yielded simultaneous liquid crystalline behaviour and appreciable conductivity in polymers with low concentrations of polar acid groups, by the formation of smectic phases in narrow aggregates. The light-responsiveness of the polymers, via reversible trans-to-cis photoisomerization of azobenzene groups, and the local activation of conductivity at relatively low temperatures, opens the possibility to prepare polymer electrolytes for energy conversion and storage, whose conductivity could be controlled and optimised by external stimuli, including light irradiation.

Evaluation of Polymeric Materials for Chemical Enhanced Oil Recovery

Polymer flooding is a promising enhanced oil recovery (EOR) technique; sweeping a reservoir with a dilute polymer solution can significantly improve the overall oil recovery. In this overview, polymeric materials for enhanced oil recovery are described in general terms, with specific emphasis on desirable characteristics for the application. Application-specific properties should be considered when selecting or developing polymers for enhanced oil recovery and should be carefully evaluated. Characterization techniques should be informed by current best practices; several are described herein. Evaluation of fundamental polymer properties (including polymer composition, microstructure, and molecular weight averages); resistance to shear/thermal/chemical degradation; and salinity/hardness compatibility are discussed. Finally, evaluation techniques to establish the polymer flooding performance of candidate EOR materials are described.

One-pot surfactant-free modulation of size and functional group distribution in thermoresponsive microgels

Control over the size and functional group distribution of soft responsive hydrogel particles is essential for applications such as drug delivery, catalysis and chemical sensing. Traditionally, targeted functional group distributions are achieved with semi-batch techniques which require specialized equipment, while the preparation of size-tailored particles typically involves the use of surfactants. Herein, we present a simple and robust surfactant-free method for the modulation of size and carboxylic acid functional group distribution in poly(N-isopropylacrylamide) thermoresponsive microgels, employing reaction pH as the single experimental parameter. The varying distributions of carboxylic acid residues arise due to differences in kinetic reactivity, which are a function of the degree of dissociation of methacrylic acid, and thus of reaction pH. Incorporated charged residues induce a surfactant-like action during the particle nucleation stage, and impact the final particle size. Characterization with dynamic light scattering, and electron microscopy consistently supports the pH-tailored morphology of the microgels. A mathematical model which accounts for particle deformation on the imaging substrate also shows excellent agreement with the experimental results.

Making the Most of Parameter Estimation: Terpolymerization Troubleshooting Tips

Multi-component polymers can provide many advantages over their homopolymer counterparts. Terpolymers are formed from the combination of three unique monomers, thus creating a new material that will exhibit desirable properties based on all three of the original comonomers. To ensure that all three comonomers are incorporated (and to understand and/or predict the degree of incorporation of each comonomer), accurate reactivity ratios are vital. In this study, five terpolymerization studies from the literature are revisited and the ‘ternary’ reactivity ratios are re-estimated. Some recent studies have shown that binary reactivity ratios (that is, from the related copolymer systems) do not always apply to ternary systems. In other reports, binary reactivity ratios are in good agreement with terpolymer data. This investigation allows for the comparison between previously determined binary reactivity ratios and newly estimated ‘ternary’ reactivity ratios for several systems. In some of the case studies presented herein, reactivity ratio estimation directly from terpolymerization data is limited by composition restrictions or ill-conditioned systems. In other cases, we observe similar or improved prediction performance (for ternary systems) when ‘ternary’ reactivity ratios are estimated directly from terpolymerization data (compared to the traditionally used binary reactivity ratios). In order to demonstrate the advantages and challenges associated with ‘ternary’ reactivity ratio estimation, five case studies are presented (with examples and counter-examples) and troubleshooting suggestions are provided to inform future work.