Critical Solution Temperature Research Articles

Strong and Thermo-Switchable Gel Adhesion Based on UCST-Type Phase Transition in Deep Eutectic Solvent.

It remains a great challenge to achieve strong and reversible hydrogel adhesion. Hydrogel adhesives also suffer from poor environmental stability due to dehydration. To overcome these problems, here reversible adhesive gels are designed using a new switching mechanism and new solvent. For the first time, the study observes UCST (upper critical solution temperature)-type thermosensitive behaviors of poly(benzyl acrylate) (PBnA) polymer and gel in menthol:thymol deep eutectic solvents (DESs). The temperature-induced phase transition allows adjusting cohesive force, and hence adhesion strength of PBnA gels by temperature. To further improve the mechanical and adhesion properties, a peptide crosslinker is used to allow energy dissipation when deforming. The resulting eutectogel exhibits thermal reversible adhesion with a high switching ratio of 14.0. The adhesion strength at attachment state reaches 0.627MPa, which is much higher than most reversible adhesive hydrogels reported before. The low vapor pressure of DES endows the gel excellent environmental stability. More importantly, the gel can be repeatedly switched between attachment and detachment states. The strong and reversible gel adhesive is successfully used to design soft gripper for the transport of heavy cargos and climbing robot capable of moving on vertical and inverted surface in a manner similar to gecko.

Asymmetry in Polymer-Solvent Interactions Yields Complex Thermoresponsive Behavior.

We introduce a lattice framework that incorporates elements of Flory-Huggins solution theory and the q-state Potts model to study the phase behavior of polymer solutions and single-chain conformational characteristics. Without empirically introducing temperature-dependent interaction parameters, standard Flory-Huggins theory describes systems that are either homogeneous across temperatures or exhibit upper critical solution temperatures. The proposed Flory-Huggins-Potts framework extends these capabilities by predicting lower critical solution temperatures, miscibility loops, and hourglass-shaped spinodal curves. We particularly show that including orientation-dependent interactions, specifically between monomer segments and solvent particles, is alone sufficient to observe such phase behavior. Signatures of emergent phase behavior are found in single-chain Monte Carlo simulations, which display heating- and cooling-induced coil-globule transitions linked to energy fluctuations. The framework also capably describes a range of experimental systems. Importantly, and by contrast to many prior theoretical approaches, the framework does not employ any temperature- or composition-dependent parameters. This work provides new insights regarding the microscopic physics that underpin complex thermoresponsive behavior in polymers.

Liposomes bearing poly(hydroxyethyl acrylate-co-ethyl vinyl sulfide) and indocyanine green and their temperature, oxidation, and near infrared-responsive release property

Liposomes are widely used for smart delivery due to their biodegradability and biocompatibility. Recently, liposomes have been developed to respond to dual and multi-stimuli. This development leads to the potential for superior in vitro and in vivo drug delivery in the future. In this study, egg PC liposomes responsive to temperature, oxidation, and NIR irradiation were prepared by modifying the liposomal membranes with poly(hydroxyethyl acrylate-co-ethyl vinyl sulfide) (P(HEA-co-EVS)) and including indocyanine green (ICG) in the liposomes.The copolymer was found to exhibit a lower critical solution temperature (LCST) and it was oxidizable and surface-active.On the TEM photos of the liposomes, multi-lamellar vesicles were found and the size was in accordance with the hydrodynamic diameter. The liposomes released their payload in response to H2O2 concentration possibly because the EVS was oxidized by the oxidizing agent. The liposome exhibited a temperature-responsive release possibly due to the thermal contraction of the copolymer chains.In addition, the release was triggered when a near-infrared(NIR) laser was irradiated to the liposome suspensions. Under NIR irradiation, the photosensitizer (i.e. ICG) can generate heat and reactive oxygen species, which, in turn, would induce the conformational and polarity change of the polymer chains, leading to a release.

Tunable coffee-ring patterns of sessile suspension droplets through silica particle encapsulation with thermo-responsive block copolymers

Silica (Si) particles coated with poly(methyl methacrylate-b-N-isopropylacrylamide) (PMMA-b-PNIPAM) block copolymers (Si-PM-PN particles) were engineered to mitigate the coffee-ring effect (CRE) frequently encountered during the drying process of particulate suspensions. Leveraging the thermo-responsive transition between the hydrophilic and hydrophobic states of PNIPAM, with its lower critical solution temperature (LCST) around 32 °C, enabled precise adjustment of the CRE. Through microrheological analysis using multi-speckle diffusing wave spectroscopy and observation under an optical microscope, the dynamic behaviors of Si-PM-PN particles in sessile suspension droplets during drying were scrutinized both below and above the LCST. Above the LCST, the Si-PM-PN particles exhibited hydrophobic characteristics, with some migrating toward the center along the droplet interface, resulting in a more uniform particle distribution post-drying. Conversely, below the LCST, the homogeneously dispersed Si-PM-PN particles displayed rapid Brownian motion, contributing to a pronounced CRE. This approach, involving the surface treatment of particles with thermo-responsive polymers, effectively altered the droplet pattern by modulating particle interactions with the air–water interface.

A Coordinating Small Organic Molecule with Tunable Lower Critical Solution Temperature for Efficient Management of Solar Radiation.

Structurally well-defined small molecules with lower critical solution temperature (LCST) behavior offer enormous prospects for fine-tuning their phase transition properties to be "on-demand" applied in the specific scene but are still underexplored. Herein, a novel amphiphilic small LCST molecule is rationally designed and synthesized. The molecule, namely TG, features a conjugation of multiple short ethylene glycol (EG) chains with the functional coordinating terpyridine (Tpy) moiety. The molecule TG demonstrates excellent LCST behavior down to 0.05× 10-3 m in a water solution. And a cloud point Tcp = 30.9°C with a very short thermal hysteresis ΔT = 0.2°C and good reversibility can be achieved when c = 0.1× 10-3 m. The excellent LCST properties of TG have enabled its successful performance as the smart window for solar radiation management with the ∆Tlum, ∆TIR, and ∆Tsol being 83.6%, 49.1%, and 67.2%, respectively. Moreover, the presence of Tpy moiety in TG enables its coordination with Ru3+ and the resulting complex also exhibits modulated LCST behavior with different concentration-dependent Tcp. These studies would provide novel small-molecule-based scaffolds for constructing better solar radiation management systems as well as other thermal-responsive smart materials.

Light‐activated 3D printed fish‐like actuator

AbstractHydrogel‐based actuators are innovative materials that exhibit responsive and dynamic behavior in response to external stimuli, making them promising candidates for a wide range of applications in fields such as soft robotics. We employ 3D printing to create layered rectangles, using a passive ink composed of gelatin methacryloyl (GelMA) and an active ink consisting of GelMA and poly(N‐isopropylacrylamide) (PNIPAM). Our aim is to assess and compare the bending capabilities of these structures based on their layer arrangements in a buffer above the lower critical solution temperature. Therefore, an asymmetric rectangular structure is selected as the shape‐changing component in the tail of a 3D printed fish‐shaped hydrogel actuator. We show that gold nanostars integrated into the actuators serve as photothermal elements, enabling the fish tail to repeatedly bend when near infrared light is turned on and off. Our effort illustrates the potential of combining 3D printing, responsive hydrogels and photothermal elements with near infrared light towards soft robotic applications. This combination yields actuators capable of shape‐shifting without requiring localized light or transitioning between environments with varying temperatures.

Development and characterization of thermosensing color indicator by pH changes using a temperature-responsive polymer

Poly(NIPAM-co-AAC) (P(NI-AC)) was synthesized by changing the polymerization conditions using poly(N-isopropylacrylamide) (NIPAM) as temperature-responsive polymer and acrylic acid (AAC). Thermosensing color indicators, that changes color depending on the external temperature, were fabricated using P(NI-AC), a pH indicator, and agar. The pH of the P(NI-AC) aqueous solution increased above the lower critical solution temperature (LCST, 34°C), and a gradual pH rise and the shrinkage of aggregate diameter continued up to 70 °C under conditions with high AAC polymerization ratio. The LCST of P(NI-AC) aqueous solution with glucose decreased, and the discoloration temperature range of the thermosensing color indicator with glucose shifted to lower temperature side from 37 to 30°C. The LCST of polymer synthesized with NIPAM, AAC, and N,N-dimethylacrylamide (DMA) increased, and the discoloration temperature range of the thermosensing color indicator shifted to higher temperature side from 39 to 50°C. These results indicated that the discoloration temperature range was successfully adjusted by as much as 20 °C.

Photo‐Responsive TiO2‐Gold Nanoparticle‐Polymer Nanohybrid Exhibits Photothermal, Thermo‐Release, and Photocatalytic Effects

AbstractThe development of multi‐responsive nanohybrid systems that combine photothermia, thermo‐responsive effects and photocatalysis is a challenging topic in the research of multifunctional materials with a large field of applications. Here, we report the first example of a three‐components light‐responsive nanosystem consisting of titania, gold nanoparticles and poly‐N‐isopropylacrylamide (TiO2‐Au‐PNM). The hybrid nanostructure exhibited photothermal conversion effect upon green‐light excitation and capacity to entrap methylene blue and curcumin selected as cargo models. The formation of the nanohybrid–cargo adducts, the photothermal‐controlled cargo release triggered by green‐light irradiation (532 nm) and mediated by lower critical solution temperature (LCST), as well as the photocatalytic effect prompted by UV‐light excitation (300 nm) were demonstrated by spectroscopic techniques. The mechanism involved in the interaction of the polymeric component with the cargos was investigated by molecular modelling calculations.

High-performance PVDF/PVB blend membranes with tailored sponge-like structure and antifouling properties for beer filtration

Currently limited research reported the design of microfiltration (MF) membranes specially for handling complex food processing streams such as rough beer. This study aimed to address this knowledge gap by tailoring for the first time a new class of polyvinylidene fluoride/poly(vinyl butyral) (PVDF/PVB) blend MF membrane with highly controllable pore structure and improved anti-fouling properties, and demonstrate its potential in real rough beer filtration. Combining an unconventional nonsolvent thermally induced phase separation (NTIPS) method and a unique quinary dope solution (i.e., PVDF/PVB/PVP/DMAc/MgCl2) with lower critical solution temperature (LCST) feature, the roles of PVB content and coagulation temperature were investigated in terms of pore structure characteristics and hydrophilicity. Although both the control PVDF membrane M0 without PVB and M6 with optimal 6.0 % PVB achieved similar turbidity removal (98–100 %), M6 exhibited enhanced permeance ranging from 27 % to 12 % with increasing simulated feed complexity from containing dextran only, yeast only to yeast/dextran mixture. The contribution of fouling of these key beer components was analyzed, indicating that the co-existence of yeast and dextran significantly aggravated fouling. Combining with membrane autopsy, in real rough beer filtration M6 showed permeance of 26.7 L·m−2·h−1·bar−1 at 1 bar that was ∼70 % higher than M0. Although with ∼50 % less irreversible fouling than M0, water cleaning implemented on M6 only recovered 62.5 % of flux. The simultaneous investigations on alkaline cleaning and operating pressure found that: a reasonably low pressure seemed favorable, e.g., 63.6 L·m−2·h−1·bar−1 at 0.2 bar, achieving up to flux recovery of ∼91 % with only ∼10 % contributed by irreversible fouling. Overall this study offers a facile yet practical strategy to tailor membranes for beer filtration, serving as an inspiration for designing future membrane processes for treating complex food processing and industry waste streams.

Multistimuli responsive hydrogels with shape fix/memory capability fabricated from gold nanorod‐conjugated amino acid‐based vinyl polymer networks

AbstractFabricating robust shape‐memory hydrogels that respond to multiple external stimuli is an important challenge in facilitating gel technology for versatile applications. In this study, we report a simple approach for constructing thermo‐, redox‐, and photo‐responsive hydrogels with high mechanical strength and shape fix/memory capability. Upper critical solution temperature (UCST)‐type amino acid‐based hydrogels were facilely prepared by radical copolymerization of N‐acryloyl glycinamide (NAGAm) with cystine‐derived divinyl acrylamides (ionic cystine [NAC] or nonionic cystine‐methyl ester [NACMe]) units at different monomer concentrations (1/2 M). These hydrogels were transparent and exhibited good mechanical strength (tensile strength of 0.3–0.4 MPa and breaking elongation of 400%–700%). All hydrogels showed UCST‐type swelling‐shrinking behaviors based on thermo‐driven reversible hydrogen bonds among the PNAGAm units, and thus could be fixed into variety of shapes and recovered to the original shape by temperature manipulation. The cystine‐based crosslinkers having SS bonds served as efficient redox‐sensitive and gold‐nanorod‐(AuNR)‐adsorbing moieties; thus, AuNR could be conjugated stably and evenly into the PNAGAm/NAC hydrogel. Moreover, upon light‐irradiation, the AuNR‐conjugated hybrid hydrogel exhibited shape‐memory behavior owing to the photothermal effect of the AuNRs. These multiresponsive/functional hydrogels composed of amino acid units have considerable potential for various applications in the fields of soft actuators and biomedicines.

Preparation and performance evaluation of intelligent plugging agent for thermo‐sensitive water‐based drilling fluid

AbstractIn the process of unconventional oil and gas exploitation, the invasion of a large amount of drilling fluid into the formation is one of the most critical reasons leading to wellbore instability. A temperature‐sensitive polymer (AOS) was synthesized from acrylamide, oligo (ethylene glycol) methyl ether methacrylate (OEGMA), and sodium p‐styrene sulfonate by emulsion polymerization. The material is a solid‐free fluid with good fluidity at room temperature, after injection into the formation, the fluid is gradually transformed into hard gel above the lower critical solution temperature (LCST) (90°C), thus blocking micro‐fractures and improving wellbore stability. Infrared and NMR characterization confirmed the successful preparation of the target product. The transmittance of AOS with ambient temperature was measured by UV–vis spectrophotometer, and the LCST behavior of AOS was verified by rheological and viscoelastic measurements. The interaction mechanism between AOS and sodium bentonite was evaluated according to the American Petroleum Institute standard. The results show that after aging at 180°C, the filtration loss is reduced by 93%, and the medium permeability (100, 200 mD) formation is effectively plugged, with a plugging efficiency is as high as 74.7%.

Synthesis of novel stimuli-responsive hydrogels based on polyurethane

This article describes the study of a thermo-responsive hybrid systems based on polyurethane (PU) modified with sensitive acrylamide derivates. The hybrid systems were synthesized using PU and two acrylamide derivatives (N-isopropylacrylamide (NIPA) and N-isopropylmethacrylamide (NIPMA)) in different proportions. The systems were characterized using infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic light scattering (DLS). Water-uptake capacity and sedimentation rate were also determined. The results showed that the hybrids with 30% acrylamide derivate (AD) showed a T50 of approximately 360 °C indicating that thermal degradation decreased with the addition of NIPA and NIPMA. Additionally, the incorporation of AD increases the glass transition temperature from −34 to −22 °C when 30% AD was used. The hybrids with 30% AD showed a variation in the diameters (above 60%) when the temperature was decreased from 50 to 22 °C. These changes were attributed to the hydrophilic → hydrophobic transition that occurs when measuring below and above the low critical solution temperature (LCST) of the polymer. Furthermore, the extra methyl group in the structure of NIPMA makes the collapse less pronounced than in NIPA, decreasing the relative diameter change by 10%. Sedimentation tests showed that the addition of the hybrid hydrogels in the sand increased the time of decantation by 60%. So, the combination of two thermo-responsive polymers to alter the hydrophilic/hydrophobic balance allows these polymers to modify their conformation at a specific temperature and could be potentially useful as self-suspending support agents or drug delivery systems.

Ion‐Mediated Gelation of Thermo‐Responsive Cellulose Nanofibril/Poly(N‐isopropylacrylamide) Hybrid Hydrogels with Tunable De‐Swelling Kinetics

AbstractThe tunability of the lower critical solution temperature (LCST) of poly(N‐isopropylacrylamide) (PNIPAM) to lower or higher temperatures, as well as the ease of modulation of the LCST phase transition kinetics broadens the scope of application of PNIPAM‐based materials in biomedical fields. This work reports a facile approach to formulate a smart, injectable cellulose nanofibril (CNF)/PNIPAM hybrid gel. Hofmeister salts are used to induce ion‐mediated gelation of the nanofibrils and PNIPAM chains, resulting in an interpenetrating network (IPN) structure. From rheological measurements, the hybrid material displays excellent structural integrity at room temperature and tunable thermo‐stiffening around body temperature. De‐swelling kinetics can be modulated by varying the nature and concentration of the Hofmeister ion used. The successful realization of the IPN hybrid gel structure is dependent on the molecular weight of PNIPAM used. Moreover, the hybrid gels show good thermo‐reversibility during thermal cycling, as well as excellent injectability and remarkable self‐healing post‐injection, owing to shear‐thinning and thixotropic characters. Since rheology is a crucial technique in the analysis of soft matter and flow behavior is fundamental for the design and synthesis of application‐specific viscoelastic materials, the work reported herein provides a rheological basis for careful design and synthesis of smart gels.

Cartilage-Inspired, High-Strength, and Heat-Tolerant Lubricating Hydrogels by Macrophase Separation.

Hydrogels are considered as a potential cartilage replacement material based on their structure being similar to natural cartilage, which are of great significance in repairing cartilage defects. However, it is difficult for the existing hydrogels to combine the high load bearing and low friction properties (37 °C) of cartilage through sample methods. Herein, we report a facile and new fabrication strategy to construct the PNIPAm/EYL hydrogel by using the macrophase separation of supersaturated N-isopropylacrylamide (NIPAm) monomer solution to promote the formation of liposomes from egg yolk lecithin (EYL) and asymmetric template method. The PNIPAm/EYL hydrogels possess a relatively high compressive strength (more than 12 MPa), fracture energy (9820 J/m2), good fatigue resistance, lubricating properties, and excellent biocompatibility. Compared with the PNIPAm hydrogel, the friction coefficient (COF 0.046) of PNIPAm/EYL hydrogel is reduced by 50%. More importantly, the COF (0.056) of PNIPAm/EYL hydrogel above lower critical solution temperature (LCST) does not increase significantly, exhibiting heat-tolerant lubricity. The finite element analysis further proves that PNIPAm/EYL hydrogel can effectively disperse the applied stress and dissipate energy under load conditions. This work not only provides new insights for the design of high-strength lubricating hydrogels but also lays a foundation for the treatment of cartilage injury as a substitute material.

Influence of PEG-PPG-PEG Block Copolymer Concentration and Coagulation Bath Temperature on the Structure Formation of Polyphenylsulfone Membranes.

The effect of amphiphilic block copolymer polyethylene glycol (PEG)-polypropylene glycol (PPG)-PEG concentration in the polyphenylsulfone (PPSU) casting solution and coagulation bath temperature (CBT) on the structure, separation, and antifouling performance of PPSU ultrafiltration membranes was studied for the first time. According to the phase diagram obtained, PPSU/PEG-PPG-PEG/N-methyl-2-pyrrolidone (NMP) systems are characterized by a narrow miscibility gap. It was found that 20 wt.% PPSU solutions in NMP with the addition of 5-15 wt.% of PEG-PPG-PEG block copolymer feature upper critical solution temperature, gel point, and lower critical solution temperature. Membrane composition and structure were studied by Fourier-transform infrared spectroscopy, scanning electron and atomic force microscopies, and water contact angle measurements. The addition of PEG-PPG-PPG to the PPSU casting solution was found to increase the hydrophilicity of the membrane surface (water contact angle decreased from 78° for the reference PPSU membrane down to 50° for 20 wt.%PPSU/15 wt.% PEG-PPG-PEG membrane). It was revealed that the pure water flux increased with the rise of CBT from 18-20 L·m-2·h-1 for the reference PPSU membrane up to 38-140 L·m-2·h-1 for 20 wt.% PPSU/10-15 wt.% PEG-PPG-PEG membranes. However, the opposite trend was observed for 20 wt.% PPSU/5-7 wt.% PEG-PPG-PEG membranes: pure water flux decreased with an increase in CBT. This is due to the differences in the mechanism of phase separation (non-solvent-induced phase separation (NIPS) or a combination of NIPS and temperature-induced phase separation (TIPS)). It was shown that 20 wt.% PPSU/10 wt.% PEG-PPG-PEG membranes were characterized by significantly higher antifouling performance (FRR-81-89%, DRr-26-32%, DRir-10-20%, DT-33-45%) during the ultrafiltration of bovine serum albumin solutions compared to the reference PPSU membrane prepared at different CBTs (FRR-29-38%, DRr-6-14%, DRir-74-89%, DT-88-94%).

Poly(N-isopropylacrylamide)-based hydrogel carrier containing Prussian blue for thermally controlled release

A hydrogel consisted of poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAAm-co-AA) and Prussian blue (PB) was synthesized for a cargo carrier by controlling the release of organic dye under near infrared (NIR) light. The AA moiety of the hydrogel provided chemical bonding with Fe (III) ions for further PB formation. Biocompatible, NIR-responsive PB generated heat and the heat was transferred to the hydrogel. The NIPAAm moiety in the hydrogel was shrunken because of the low critical solution temperature behavior of the hydrogel, and the hydrogel released the loaded dye with 62%. These results suggest dye-loaded hydrogel as a prospective platform for light-triggered carriers.

Synthesis of Thermoresponsive Chitosan-graft-Poly(N-isopropylacrylamide) Hybrid Copolymer and Its Complexation with DNA.

A hybrid synthetic-natural, thermoresponsive graft copolymer composed of poly(N-isopropyl acrylamide) (PNIPAM) side chains, prepared via RAFT polymerization, and a chitosan (Chit) polysaccharide backbone, was synthesized via radical addition-fragmentation reactions using the "grafting to" technique, in aqueous solution. ATR-FTIR, TGA, polyelectrolyte titrations and 1H NMR spectroscopy were employed in order to validate the Chit-g-PNIPAM copolymer chemical structure. Additionally, 1H NMR spectra and back conductometric titration were utilized to quantify the content of grafted PNIPAM side chains. The resulting graft copolymer contains dual functionality, namely both pH responsive free amino groups, with electrostatic complexation/coordination properties, and thermoresponsive PNIPAM side chains. Particle size measurements via dynamic light scattering (DLS) were used to study the thermoresponsive behavior of the Chit-g-PNIPAM copolymer. Thermal properties examined by TGA showed that, by the grafting modification with PNIPAM, the Chit structure became more thermally stable. The lower critical solution temperature (LCST) of the copolymer solution was determined by DLS measurements at 25-45 °C. Furthermore, dynamic and electrophoretic light scattering measurements demonstrated that the Chit-g-PNIPAM thermoresponsive copolymer is suitable of binding DNA molecules and forms nanosized polyplexes at different amino to phosphate groups ratios, with potential application as gene delivery systems.

Bi-layered hydrogel conduit integrating microneedles for enhanced neural recording and stimulation therapy in peripheral nerve injury repair

Nerve conduit is an alternative strategy in peripheral nerve injuries (PNI) treatment both for neural signals recording and therapeutic electrical stimulation (ES). Most conventional conduits suffer from surgical suturing and lacking real-time insights of nerve recovery, as well as failing in integrating therapy strategies. Herein, we introduce a bi-layered hydrogel conduit with microneedles (BHCM), in which poly (N-isopropylacrylamide) (PNIPAm)-incorporated polyethyleneimine (PEI) forms the outer layer for conductivity and electro-driven drug loading and release, whereas PNIPAm/alginate/tannic acid hydrogel (PNIPAm/SA/TA) forms the inner layer to ensure biocompatible mechanics and strong tissue adhesion. Meanwhile, the differences in doping manipulated different critical solution temperature (LCST) and swelling between the double layers determine the self-curling performance. Therefore, the BHCM responds to temperature and self-curls into conduit to wrap and bind to sciatic nerve, avoiding the complicated suturing and enhancing the interfacial electrical transmission. By puncturing the epineurium, the microneedles strongly enhance the electrochemical performance, and synergistically facilitate controllable drug delivery as well as electrical stimulation and recording efficiency. Further, BHCM is demonstrated to regulate macrophage polarization from M1 to M2 through electrically stimulated Rhein release, thereby reducing inflammation and facilitating diabetic PNI repair. The present design aims to improve biosafety, surgical simplicity to realize overall recovery of injured nerves, making it a promising candidate for advanced peripheral nerve repair strategies.

Isolation of nucleic acids using liquid–liquid phase separation of pH-sensitive elastin-like polypeptides

Extraction of nucleic acids (NAs) is critical for many methods in molecular biology and bioanalytical chemistry. NA extraction has been extensively studied and optimized for a wide range of applications and its importance to society has significantly increased. The COVID-19 pandemic highlighted the importance of early and efficient NA testing, for which NA extraction is a critical analytical step prior to the detection by methods like polymerase chain reaction. This study explores simple, new approaches to extraction using engineered smart nanomaterials, namely NA-binding, intrinsically disordered proteins (IDPs), that undergo triggered liquid–liquid phase separation (LLPS). Two types of NA-binding IDPs are studied, both based on genetically engineered elastin-like polypeptides (ELPs), model IDPs that exhibit a lower critical solution temperature in water and can be designed to exhibit LLPS at desired temperatures in a variety of biological solutions. We show that ELP fusion proteins with natural NA-binding domains can be used to extract DNA and RNA from physiologically relevant solutions. We further show that LLPS of pH responsive ELPs that incorporate histidine in their sequences can be used for both binding, extraction and release of NAs from biological solutions, and can be used to detect SARS-CoV-2 RNA in samples from COVID-positive patients.

Thermo-thickening/amphoteric polymer nanocomposite incorporating vinyl-functionalized nano-silica as a viscosifier for high-salt and ultra-high temperature water-based drilling fluids

In the relentless extraction of oil and gas from deeper reservoirs, the harsh geological conditions pose significant rheological challenges for conventional polymer viscosifiers. Hence, the spotlight has turned to the unique potential of thermo-thickening polymers to enhance drilling fluid performance. In this study, a novel polymer nanocomposite (VMS-ATA) was designed to associate thermo-thickening responses, amphoteric characteristics, and vinyl-functionalized nano-silica (VMS) as nanofillers for the formation of a thermally stable polymer nanocomposite-bentonite hybrid system. VMS-ATA was prepared via in-situ polymerization under optimal synthetic conditions, and the unique chemical structure was analyzed using various techniques such as Fourier transform spectroscopy, proton nuclear magnetic resonance, elemental analysis, thermogravimetric analysis, X-ray spectroscopy, transmission electron microscopy, and scanning electron microscopy. The study systematically investigated the enhancement of in-situ covalent bonding characteristics of VMS on the thermo-thickening behavior of VMS-ATA, while comparing it with amine-nano-silica (AMS) incorporated in a polymer composite (AMS-CGBA). TGA analysis revealed that VMS-ATA exhibits excellent thermal stability compared to AMS-CGBA, attributed to the thermally stable VMS (370 °C) compared to AMS (355 °C). Interestingly, VMS-ATA displayed relatively stable and prolonged thermo-thickening responses (100–200 °C) owed to high thermal-induced activation responses above the lower critical solution temperature (LCST) in both salt-free and saturated salt contamination. The rheological results of VMS-ATA viscosity retention at 220 °C and 20 wt% NaCl, exceeded 60 %, which is twice that of AMS-CGBA-containing fluids. As demonstrated, VMS-ATA and AMS-CGBA exhibited similar macro-interactions with rigid imidazole and caprolactam rings, but significantly differed in their micro-interactions owed to in-situ covalent binding induced by VMS compared to hydrogen bonding in AMS. This breakthrough exhibited the potential of VMS nanofillers to effectively maintain thickening response by facilitating efficient heat distribution to minimize rapid viscosity decay and revolutionize the landscape of high-salt and high-temperature (HSHT) drilling applications.