Star-Like Branched Polyacrylamides by RAFT polymerization, Part II: Performance Evaluation in Enhanced Oil Recovery (EOR)

In the present study the performance of a series of star-like branched polyacrylamides (SB-PAMs) has been investigated in oil recovery experiments to ultimately determine their suitability as novel thickening agent for enhanced oil recovery (EOR) applications. Hereby, SB-PAMs were compared with conventional linear PAM. The effect of a branched molecular architecture on rheology, and consequently on oil recovery was discussed. Rheological measurements identified unique properties for the SB-PAMs, as those showed higher robustness under shear and higher salt tolerance than their linear analogues. EOR performance was evaluated by simulating oil recovery in two-dimensional flow-cell measurements, showing that SB-PAMs perform approximately 3–5 times better than their linear analogues with similar molecular weight. The salinity did not influence the solution viscosity of the SB-PAM, contrarily to what happens for partially hydrolyzed polyacrylamide (HPAM). Therefore, SB-PAMs are more resilient under harsh reservoir conditions, which can make them attractive for EOR applications

Enhancing the ROS Sensitivity of a Responsive Supramolecular Hydrogel Using Peroxizyme Catalysis

Hydrogels that can disintegrate upon exposure to reactive oxygen species (ROS) have the potential for targeted drug delivery to tumor cells. In this study, we developed a diphenylalanine (FF) derivative with a thioether phenyl moiety attached to the N-terminus that can form supramolecular hydrogels at neutral and mildly acidic pH. The thioether can be oxidized by ROS to the corresponding sulfoxide, which makes the gelator hydrolytically labile. The resulting oxidation and hydrolysis products alter the polarity of the gelator, leading to disassembly of the gel fibers. To enhance ROS sensitivity, we incorporated peroxizymes in the gels, namely, chloroperoxidase CiVCPO and the unspecific peroxygenase rAaeUPO. Both enzymes accelerated the oxidation process, enabling the hydrogels to collapse with 10 times lower H2O2 concentrations than those required for enzyme-free hydrogel collapse. These ROS-responsive hydrogels could pave the way toward optimized platforms for targeted drug delivery in the tumor microenvironment

Naked-Eye Thiol Analyte Detection via Self-Propagating, Amplified Reaction Cycle

We present an approach for detecting thiol analytes through a self-propagating amplification cycle that triggers the macroscopic degradation of a hydrogel scaffold. The amplification system consists of an allylic phosphonium salt that upon reaction with the thiol analyte releases a phosphine, which reduces a disulfide to form two thiols, closing the cycle and ultimately resulting in exponential amplification of the thiol input. When integrated in a disulfide cross-linked hydrogel, the amplification process leads to physical degradation of the hydrogel in response to thiol analytes. We developed a numerical model to predict the behavior of the amplification cycle in response to varying concentrations of thiol triggers and validated it with experimental data. Using this system, we were able to detect multiple thiol analytes, including a small molecule probe, glutathione, DNA, and a protein, at concentrations ranging from 132 to 0.132 μM. In addition, we discovered that the self-propagating amplification cycle could be initiated by force-generated molecular scission, enabling damage-triggered hydrogel destruction