Cloud Point Temperature Research Articles

PNIPAM Mesoglobules in Dependence on Pressure.

Poly(N-isopropylacrylamide) (PNIPAM) in aqueous solution forms mesoglobules above its cloud point temperature Tcp. While these are small and compact at atmospheric pressure, they are large and water-rich at high pressure. To identify the transition between these states, we employed optical microscopy and carried out isothermal pressure scans. Using very small angle neutron scattering, we determined the size and water content of the mesoglobules in pressure scans at different temperatures above Tcp. We observe a distinct transition at pressures of 35-55 MPa with the transition pressure depending on temperature. While the transition is smooth at high temperatures, i.e., far away from the coexistence line, it is abrupt at low temperatures, i.e., close to the coexistence line. Hence, at high temperatures, the swelling of the mesoglobules dominates, whereas at low temperatures, the coalescence of mesoglobules prevails. Subsequently decreasing the pressure results in a gradual deswelling of the mesoglobules at high temperature. In contrast, at low temperatures, small and compact mesoglobules form, but the large aggregates persist. We conclude that, on the time scale of the experiment, the disintegration of the large swollen aggregates into small and compact mesoglobules is only partially possible. Erasing the history by cooling the sample at the maximum pressure into the one-phase state does not result in qualitative changes for the behavior with the only difference that Fewer mesoglobules are formed when the pressure is decreased again. The newly identified transition line separates the low-pressure from the high-pressure regime.

Spectrophotometric determination of zinc in blood and food samples using an air-assisted rapid synergistic-cloud point extraction method based on deep eutectic solvents

At room temperature, an air-assisted rapid synergistic cloud point extraction (AA-RS-CPE) method based on deep eutectic solvent (DES) was presented to determine Zn (II) traces in various samples. Nonanoic acid and L-menthol formed the synergistic reagent (DES) in a 2:1 mole ratio to reduce both time and cloud point temperature. Air cycles were used to maximize recovery and accelerate cloudy solution formation. The 4,4-dimethyl-2,6-dioxo-N-phenylcyclohexanecarbothioamide (DDPCCTA) and TritonX-100 were used as ligand and surfactant, respectively. The validation parameters, including the calibration curve linearity (0.2-900µgL-1), the limit of detection (LOD = 0.10µgL-1), the enhancement factor (EF = 120), and the preconcentration factor (PE = 100), were calculated. Additionally, the accuracy of the AA-RS-DES-CPE approach was proved by two certified reference materials (CRMs). Finally, the three greenness tools, the Blue Applicability Grade Index (BAGI), the Sample Preparation Metric of Sustainability (SPMS), and the Analytical Greenness Metric for Sample Preparation (AGREEprep), were used to evaluate the environmental sustainability values, health hazards, and applicability of this method. This approach was improved to be safer and more environmentally friendly than existing methods, with high application potential.

Gas hydrate inhibition by urea and its blends with vinyl lactam polymer: Paving the way to green hybrid inhibitors

Urea is an environmentally benign substance considered a promising gas hydrate inhibitor in flow assurance. Nevertheless, its effect on gas hydrate formation kinetics remains poorly understood. This study investigates the impact of urea and hybrid urea/polymer KHI samples on the nucleation and growth kinetics of sII natural gas hydrates. Hydrate formation was observed at a lower onset temperature with increasing urea and polymer concentration. The nucleation of sII hydrate in aqueous urea solutions occurred at a higher subcooling (7.50 ± 0.58 K at 30 mass%) than in pure water (5.17 ± 0.69 K). These findings indicate that urea acts as a nucleation inhibitor of sII hydrates, although its capacity is not as potent as that of polymer KHI.The analysis of the hydrate nucleation probability distributions revealed that the sII hydrate nucleation rate exhibited a significant decline, approximately one order of magnitude, at subcooling of 5.3–6 K for 20 mass% urea compared to water. A similar behavior was noticed in an aqueous solution of polymer KHI. Urea has succeeded in providing a total benefit of up to 10 K in hydrate onset temperature due to a shift in the hydrate stability zone and nucleation retardation.Consequently, urea is a green dual-acting anti-hydrate chemical that inhibits the formation of sII hydrates by thermodynamic and kinetic mechanisms. Besides, adding 10 mass% urea increases the cloud point temperature of vinyl lactam polymer Luvicap 55W by 14 K. Urea is an additive that considerably augments the stability of the polymer in aqueous solutions at elevated temperatures. These findings make urea an effective and environmentally friendly top-up inhibitor that significantly enhances the anti-hydrate properties of polymer KHI.

Enhanced removal of toxic Disperse Blue 35 dye through cloud point extraction: influence of parameters and solvent regeneration

Abstract The release of the dye Disperse Blue 35 (DB35) into water has serious environmental and health consequences, due to its toxicity and resistance to degradation. This paper investigates the effectiveness of cloud point extraction (CPE) to remove this industrial dye from aqueous solution by Lutensol AO7 and Triton X-114, two environmentally friendly nonionic surfactants. First, the partial phase diagrams of the water–surfactant binary systems are constructed. Then, the effects of pollutants, sodium sulfate and cetyltrimethylammonium bromide on the cloud point temperature (T c) are determined. The experimental results are expressed by four responses: Extraction efficiency (E), residual concentrations of solute and surfactant in the dilute phase (X s,w and X t,w, respectively) and the volume fraction of coacervate (Ф c). An empirical smoothing method was applied. For each parameter, the results obtained were modeled using the response surface methodology (RSM) and represented on three-dimensional diagrams. The results show that the efficiency of dye extraction with Lutensol AO7 and Triton X-114 at a concentration of 6 wt% is about 95 % and 82 %, respectively. The influence of salt and ionic surfactant on the effectiveness of CPE for the removal of DB 35 dye was determined. The regeneration of surfactant was only achieved by pH adjustment.

Molecularly Engineered Supramolecular Thermoresponsive Hydrogels with Tunable Mechanical and Dynamic Properties.

Synthetic supramolecular polymers and hydrogels in water are emerging as promising biomaterials due to their modularity and intrinsic dynamics. Here, we introduce temperature sensitivity into the nonfunctionalized benzene-1,3,5-tricarboxamide (BTA-EG4) supramolecular system by incorporating a poly(N-isopropylacrylamide)-functionalized (BTA-PNIPAM) moiety, enabling 3D cell encapsulation applications. The viscous and structural properties in the solution state as well as the mechanical and dynamic features in the gel state of BTA-PNIPAM/BTA-EG4 mixtures were investigated and modulated. In the dilute state (c ∼μM), BTA-PNIPAM acted as a chain capper below the cloud point temperature (Tcp = 24 °C) but served as a cross-linker above Tcp. At higher concentrations (c ∼mM), weak or stiff hydrogels were obtained, depending on the BTA-PNIPAM/BTA-EG4 ratio. The mixture with the highest BTA-PNIPAM ratio was ∼100 times stiffer and ∼10 times less dynamic than BTA-EG4 hydrogel. Facile cell encapsulation in 3D was realized by leveraging the temperature-sensitive sol-gel transition, opening opportunities for utilizing this hydrogel as an extracellular matrix mimic.

Lecithin-based micellar extraction of bioactive from pomegranate peel and its application in Indian flat bread (chapati) as a bioactive emulsifier

Micellar extraction is a sustainable, eco-friendly, and cost-efficient method for extracting and recovering phenolic and flavonoid molecules from pomegranate peel. This technique traps bioactive molecules in micelles formed by a surfactant above cloud point temperature (CPT). The influence of process variables such as lecithin concentration (8–16%), pH (3−6), temperature (40–60 °C), and NaCl concentration (8–16%) on extraction was examined and then optimized numerically. For micellar separation, lecithin and salt content were the most significant (p < 0.05). The optimal variables to maximize bioactive recovery were 13.11% (w/v) lecithin concentration, 4.13 pH at 50.88 °C, and 13.89% (w/v) NaCl concentration. 88.21% of total polyphenols (TPC) and 82.64% of total flavonoids (TFC) were recovered at optimal conditions. The yields of TPC, TFC, punicalagin (PC), ellagic acid (EAC), and total hydrolyzable tannins (THTC) were 163.36 mg gallic acid equivalent/g, 24.71 mg quercetin equivalent/g, 27.29 mg/g, 8.97 mg/g, and 112.36 mg tannic acid equivalent/g of pomegranate peel, respectively. The extract exhibited good antioxidant capacity (55.18% DPPH and 39.25% ABTS). Using liquid chromatography mass spectroscopy, total 14 additional hydrolyzable tannins compounds were identified. The changes in functional groups and thermal properties of the micellar pomegranate peel extract enriched lecithin (MPEL) and pomegranate peel were effectively correlated by fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. MPEL was employed to prepare chapatis. The staling, textural, and bioactive properties of MPEL-enriched chapatis were significantly improved as compared to the control chapatis. However, the color and sensory attributes of chapatis developed with and without lecithin were similar. Additionally, MPEL also controlled staling and microbial growth (AMC: aerobic mesophilic count and YMC: yeast and mold count) along with the retention of the texture of chapatis during the storage of 5 days at 5 and 25 °C.

Compressible Hydrogels with Stabilized Chirality from Thermoresponsive Helical Dendronized Poly(phenylacetylene)s

AbstractFabrication of chiral hydrogels from thermoresponsive helical dendronized phenylacetylene copolymers (PPAs) carrying three‐fold dendritic oligoethylene glycols (OEGs) is reported. Three different temperatures, i.e. below or above cloud point temperatures (Tcps) of the copolymers, and under freezing condition, were utilized, affording thermoresponsive hydrogels with different morphologies and mechanical properties. At room temperature, transparent hydrogels were obtained through crosslinking among different copolymer chains. Differently, opaque hydrogels with much improved mechanical properties were formed at elevated temperatures through crosslinking from the thermally dehydrated and collapsed copolymer aggregates, leading to heterogeneity for the hydrogels with highly porous morphology. While crosslinking at freezing temperature synergistically through ice templating, these amphiphilic dendronized copolymers formed hydrogels with highly porous lamellar structures, which exhibited remarkable compressible properties as human articular cartilage with excellent fatigue resistance. Amphiphilicity of the dendronized copolymers played a pivotal role in modulating the network formation during the gelation, as well as morphology and mechanical performance of the resulting hydrogels. Through crosslinking, these dendronized copolymers featured with typical dynamic helical conformations were transformed into hydrogels with unprecedently stabilized helicities due to the restrained chain mobilities in the three‐dimensional networks.

Compressible Hydrogels with Stabilized Chirality from Thermoresponsive Helical Dendronized Poly(phenylacetylene)s.

Fabrication of chiral hydrogels from thermoresponsive helical dendronized phenylacetylene copolymers (PPAs) carrying three-fold dendritic oligoethylene glycols (OEGs) is reported. Three different temperatures, i.e. below or above cloud point temperatures (Tcps) of the copolymers, and under freezing condition, were utilized, affording thermoresponsive hydrogels with different morphologies and mechanical properties. At room temperature, transparent hydrogels were obtained through crosslinking among different copolymer chains. Differently, opaque hydrogels with much improved mechanical properties were formed at elevated temperatures through crosslinking from the thermally dehydrated and collapsed copolymer aggregates, leading to heterogeneity for the hydrogels with highly porous morphology. While crosslinking at freezing temperature synergistically through ice templating, these amphiphilic dendronized copolymers formed hydrogels with highly porous lamellar structures, which exhibited remarkable compressible properties as human articular cartilage with excellent fatigue resistance. Amphiphilicity of the dendronized copolymers played a pivotal role in modulating the network formation during the gelation, as well as morphology and mechanical performance of the resulting hydrogels. Through crosslinking, these dendronized copolymers featured with typical dynamic helical conformations were transformed into hydrogels with unprecedently stabilized helicities due to the restrained chain mobilities in the three-dimensional networks.

Study of the Thermal Phase Transition of Poly(N,N-diethylacrylamide-co-N-ethylacrylamide) Random Copolymers in Aqueous Solution.

N-alkyl-substituted polyacrylamides exhibit a thermal coil-to-globule transition in aqueous solution driven by an increase in hydrophobic interactions with rising temperature. With the aim of understanding the role of N-alkyl substituents in the thermal transition, this study focuses on the molecular interactions underlying the phase transition of poly(N,N-diethylacrylamide-co-N-ethylacrylamide) random copolymers. Poly(N,N-diethylacrylamide) (PDEAm), poly(N-ethylacrylamide) (PNEAm), and their random copolymers were synthesized by free radical polymerization and their chemical structure characterized spectroscopically. It was found that the values of the cloud-point temperature increased with PNEAm content, and particle aggregation processes took place, increasing the negative charge density on their surface. The cloud-point temperature of each copolymer decreased with respect to the theoretical values calculated assuming an absence of interactions. It is attributed to the formation of intra- and interchain hydrogen bonding in aqueous solutions. These interactions favor the formation of more hydrophobic macromolecular segments, thereby promoting the cooperative nature of the transition. These results definitively reveal the dominant mechanism occurring during the phase transition in the aqueous solutions of these copolymers.

From Facile One-Pot Synthesis of Semi-Degradable Amphiphilic Miktoarm Polymers to Unique Degradation Properties.

We report a one-pot synthesis of well-defined A5B and A8B miktoarm star-shaped polymers where N,N-dimethylaminoethyl methacrylate (DMAEMA) and various cyclic esters such as ε-caprolactone (ε-CL), lactide (LA) and glycolide (GA) were used for the synthesis. Miktopolymers were obtained by simultaneously carrying out atom transfer radical polymerization (ATRP) of DMAEMA, ring-opening polymerization (ROP) of cyclic esters, and click reaction between the azide group in gluconamide-based (GLBr5-Az) or lactonamide-based (GLBr8-Az) ATRP initiators and 4-pentyn-1-ol. The relatively low dispersity indices of the obtained miktoarm stars (Đ = 1.2-1.6) indicate that control over the polymerization processes was sustained despite almost complete monomers conversions (83-99%). The presence of salts from phosphate-buffered saline (PBS) in polymer solutions affects the phase transition, increasing cloud point temperatures (TCP) values. The critical aggregation concentration (CAC) values increased with a decreasing number of average molecular weights of the hydrophobic fraction. Hydrolytic degradation studies revealed that the highest reduction of molecular weight was observed for polymers with PCL and PLGCL arm. The influence of the composition on the miktopolymers hydrophilicity was investigated via water contact angle (WCA) measurement. Thermogravimetric analysis (TGA) disclosed that the number of arms and their composition in the miktopolymer affects its weight loss under the influence of temperature.

Effect of End Groups on the Cloud Point Temperature of Aqueous Solutions of Thermoresponsive Polymers: An Inside View by Flory-Huggins Theory.

In an effort to gain insight into the origin of the effects of end groups on the cloud point temperature (Tcp) as a function of the polymer molar mass of thermoresponsive polymers with lower critical solution behavior in dilute aqueous solutions, we use the Flory-Huggins (FH) theory amended for end groups. The theory was applied to available experimental data sets of poly(N-isopropylacrylamide) (PNIPAM), poly(4-vinylbenzyl methoxytris(oxyethylene) ether) (PTEGSt), and poly(α-hydro-ω-(4-vinylbenzyl)tetrakis(oxyethylene) ether) (PHTrEGSt). The theory relates the variations in TcpM,ϕcp for different end groups to the effective FH χ parameter of the end groups and explains the qualitative notion that the influence of the end groups is related to the hydrophobicity/hydrophilicity of the end groups relative to that of the so called intrinsic TcpM,ϕcp response of a polymer without end groups. The limits to the applicability of the FH theory are established, and a set of possible theoretical improvements is considered. The ultimate scrutiny of the simple FH theory and suggested improved theories must await the measurement of truly thermodynamic cloud points; the available cloud points are merely estimations of the thermodynamic cloud point, for which the deviation to the true cloud point cannot be established with sufficient accuracy.

High-substituted hydroxypropyl cellulose prepared by homogeneous method and its clouding and self-assembly behaviors

Hydroxypropyl cellulose (HPC) is a sustainable cellulose derivative valued for its excellent biocompatibility and solubility and is widely used in various fields. Recent scientific research on high-substituted HPC mainly focused on its efficient preparation and phase transition behavior. Herein, a novel strategy of high-substituted HPC synthesis was demonstrated by employing DMSO/TBAF·3H2O as a cellulose solvent, exhibiting more efficiency than traditional approaches. High-substituted HPC prepared has remarkable thermal stability, exceptional hydrophilicity, and satisfactory solubility. Phase transition behavior of HPC with varying molar degrees of substitution (MS) was delved and a notable negative correlation between MS and cloud point temperature (TCP), was revealed, particularly evident at an MS of 12.3, where the TCP drops to 33 °C. Moreover, a unique self-assembly behavior featuring structural color and responsiveness to force in a solvent-free environment emerged when the MS exceeded 10.4. These insights comprehensively strengthen the understanding and knowledge of high-substituted HPC, simultaneously paving the way for further HPC investigation and exploitation.

Synergistic topological and supramolecular control of Diels-Alder reactivity based on a tunable self-complexing host-guest molecular switch.

Compartmentalization and binding-triggered conformational change regulate many metabolic processes in living matter. Here, we have synergistically combined these two biorelevant processes to tune the Diels-Alder (DA) reactivity of a synthetic self-complexing host-guest molecular switch CBPQT4+ -Fu, consisting of an electron-rich furan unit covalently attached to the electron-deficient cyclobis(paraquat-p-phenylene) tetrachloride (CBPQT4+ , 4Cl- ) host. This design allows CBPQT4+ -Fu to efficiently compartmentalize the furan ring inside its host cavity in water, thereby protecting it from the DA reaction with maleimide. Remarkably, the self-complexed CBPQT4+ -Fu can undergo a conformational change through intramolecular decomplexation upon the addition of a stronger binding molecular naphthalene derivative as a competitive guest, triggering the DA reaction upon addition of a chemical regulator. Remarkably, connecting the guest to a thermoresponsive lower critical solution temperature (LCST) copolymer regulator controls the DA reaction on command upon heating and cooling the reaction media beyond and below the cloud point temperature of the copolymer, representing a rare example of decreased reactivity upon increasing temperature. Altogether, this work opens up new avenues towards combined topological and supramolecular control over reactivity in synthetic constructs, enabling control over reactivity through molecular regulators or even mild temperature variations.

ПОВЕРХНОСТНО-АКТИВНЫЕ СВОЙСТВА АЛКАНОЛАМИДОВ

The indicators of the wetting ability of surfaces with aqueous solutions of the studied alkanolamides based on distilled fatty acids of rapeseed (DKRMA) and sunflower (DKPMA) oils were studied and monoethanolamide. The sizes of surfactant components were diagnosed using high-precision instruments: a DataPhysics DCAT 21 tensiometer and a 90Plus/BI-MAS particle size analyzer. The contact angles of wetting of glass (hydrophilic) and paraffin (hydrophobic) surfaces with DCPMA solutions at concentrations above the critical micelle concentration (CMC) (1.5-2.0 g/dm3) reached values of 33.0-34.0º. For DKRMA, the contact angles were 34.0-35.0º for the glass surface and 36.0-37.0º for the paraffin surface. It was found that before CMC (at a surfactant concentration of 0.5-1.0 g/dm3), the hydrodynamic radii of the components are in the range of 120.7 - 121.1 nm. Outside the CMC, the hydrodynamic radii of particles of surfactant micelles reach values of 221.3 - 221.6 nm. It was revealed that the synthesized alkanolamides belonged to the category of monodisperse systems according to the fractional composition of the particles of the dispersed phase. The latter is regulated by the uniformity of dispersed particle sizes. The latter is regulated by the uniformity of dispersed particle sizes. Depending on the average size of dispersed particles, the surfactants under study are highly dispersed systems (divided by particle size of the dispersed phase). The surfactants under study are highly dispersed systems, in accordance with the classification by particle size of the dispersed phase depending on the average size of the dispersed particles. It has been proven that the products take an intermediate position between nano- and microparticles. The cloud point temperature (81-83ºС) was measured and the hydrophilic-lipophilic balance (HLB) (11.8-11.9) of the surfactants under study was calculated. The obtained HLB values mean that alkanolamides belong to the group of “oil in water” emulsions. The pH of aqueous solutions of surfactants at a concentration of 10.0 g/dm3 was 7-8. Neonol AF 9-12 was used as a control surfactant.

Degradable polymers with adjustable thermoresponsiveness based on multicomponent polymerization and molecular recognition

Degradable PEG-based polymers with disulfide linkages and adamantyl groups are synthesized through multicomponent polymerization. The cloud point temperature and the zeta potential of the polymers can be adjusted through molecular recognition.

Temperature response behavior of poly(1-vinyl-3-methylimidazole dimethyl phosphate-co-N-isopropylacrylamide) in aqueous and ester solutions driven by hydrogen bonding

A series of poly(1-vinyl-3-methylimidazole dimethyl phosphate-co-N-isopropylacrylamide) oligomers was synthesized by reversible addition-fragmentation chain transfer polymerization. The co-oligomers exhibited a pH-tunable lower critical solution temperature (LCST) phase transition in aqueous solutions. By changing the pH of the aqueous solution (HCI), the hydrogen bonding between the internal molecules of the co-oligomers and water molecules was weakened, which effectively reduced the cloud-point temperature. Poly(1-vinyl-3-methylimidazole dimethyl phosphate-co-N-isopropylacrylamide) oligomers exhibit an upper critical solution temperature (UCST) type of phase transition in an ester solution, which is associated with the formation and breaking of hydrogen bonds within the co-oligomers molecules. FT-IR analysis revealed the effect of temperature on hydrogen bonding between the functional groups. Energy decomposition, Electrostatic Potential (ESP), Atoms-in-Molecules (AIM), and Interaction region indicator (IRI) analyses demonstrated the presence of hydrogen bond donors N–H and imidazole ring C–H, and hydrogen bond acceptors C = O and P = O in the co-oligomers. The sites of hydrogen bonding between the co-oligomers and the solvent molecules as well as intermolecular forces were found to be the main factors contributing to the LCST/UCST-type phase transition.

Eco-Conscious Approach to Thermoresponsive Star-Comb and Mikto-Arm Polymers via Enzymatically Assisted Atom Transfer Radical Polymerization Followed by Ring-Opening Polymerization.

This study explores the synthesis, characterization, and application of a heterofunctional initiator derived from 2-hydroxypropyl cyclodextrin (HP-β-CD), having eight bromoester groups and thirteen hydroxyl groups allowing the synthesis of mikto-arm star-shaped polymers. The bromoesterification of HP-β-CD was achieved using α-bromoisobutyryl bromide as the acylation reagent, modifying the cyclodextrin (CD) molecule as confirmed by electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance (NMR), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy analysis, and differential scanning calorimetry (DSC) thermograms. The initiator's effectiveness was further demonstrated by obtaining star-comb and mikto-arm polymers via an enzymatically assisted atom transfer radical polymerization (ATRP) method and subsequent ring-opening polymerization (ROP). The ATR polymerization quality and control depended on the type of monomer and was optimized by the way of introducing the initiator into the reaction mixture. In the case of ATRP, high conversion rates for poly(ethylene oxide) methyl ether methacrylate (OEOMA), with molecular weights (Mn) of 500 g/mol and 300 g/mol, were achieved. The molecular weight distribution of the obtained polymers remained in the range of 1.23-1.75. The obtained star-comb polymers were characterized by different arm lengths. Unreacted hydroxyl groups in the core of exemplary star-comb polymers were utilized in the ROP of ε-caprolactone (CL) to obtain a hydrophilic mikto-arm polymer. Cloud point temperature (TCP) values of the synthesized polymers increased with arm length, indicating the polymers' reduced hydrophobicity and enhanced solvation by water. Atomic force microscopy (AFM) analysis revealed the ability of the star-comb polymers to create fractals. The study elucidates advancements in the synthesis and utilization of hydrophilic sugar-based initiators for enzymatically assisted ATRP in an aqueous solution for obtaining complex star-comb polymers in a controlled manner.

Thermoresponsive Property of Poly(N,N-bis(2-methoxyethyl)acrylamide) and Its Copolymers with Water-Soluble Poly(N,N-disubstituted acrylamide) Prepared Using Hydrosilylation-Promoted Group Transfer Polymerization.

The group-transfer polymerization (GTP) of N,N-bis(2-methoxyethyl)acrylamide (MOEAm) initiated by Me2EtSiH in the hydrosilylation-promoted method and by silylketene acetal (SKA) in the conventional method proceeded in a controlled/living manner to provide poly(N,N-bis(2-methoxyethyl)acrylamide) (PMOEAm) and PMOEAm with the SKA residue at the α-chain end (MCIP-PMOEAm), respectively. PMOEAm-b-poly(N,N-dimethylacrylamide) (PDMAm) and PMOEAm-s-PDMAm and PMOEAm-b-poly(N,N-bis(2-ethoxyethyl)acrylamide) (PEOEAm) and PMOEAm-s-PEOEAm were synthesized by the block and random group-transfer copolymerization of MOEAm and N,N-dimethylacrylamide or N,N-bis(2-ethoxyethyl)acrylamide. The homo- and copolymer structures affected the thermoresponsive properties; the cloud point temperature (Tcp) increasing by decreasing the degree of polymerization (x). The chain-end group in PMOEAm affected the Tcp with PMOEAmx > MCIP-PMOEAmx. The Tcp of statistical copolymers was higher than that of block copolymers, with PMOEAmx-s-PDMAmy > PMOEAmx-b-PDMAmy and PMOEAmx-s-PEOEAmy > PMOEAmx-b-PEOEAmy.

Nonionic Surfactant Blends for Enhanced Oil Recovery in High-Temperature Eagle Ford Reservoir

Summary Nonionic surfactants have proven successful and cost-effective in enhancing production from conventional and unconventional reservoirs. However, studies into the mechanism and performance of nonionic surfactants have been limited to reservoirs with temperatures below 200°F due to the temperature-dependent physiochemical properties, especially cloudpoint (CP). In this study, nonionic-ionic surfactant blends were designed to create nonionic systems with cloudpoint temperatures (CPTs) above 300°F for wettability alteration in high-temperature reservoirs like the Eagle Ford Shale in Texas, USA. Through CP, wettability, interfacial tension (IFT), and spontaneous imbibition experiments, 22 commercial surfactant samples (individual and blends) were investigated. Results showed that the amount of ionic cosurfactant affected thermal stability, with increasing concentration leading to increasing CPT. Wettability alteration was dependent not only on temperature but also on the class of ionic cosurfactant. Cationic cosurfactants were superior at improving nonionic surfactants’ thermal stability. However, they resulted in oil-wet contact angles (CAs) with increasing temperature. On the other hand, anionic cosurfactants displayed better synergy in terms of wettability alteration, creating strongly water-wet and intermediate-wet CAs at high temperatures. Therefore, the focus was placed on nonionic-anionic surfactant blends for the reservoir samples used in this study. Stable surfactant blends with CPTs from 316°F to 348°F were successfully created for enhanced oil recovery (EOR) applications at high-temperature conditions. Spontaneous imbibition studies using these blends indicated improved recovery by up to 173%. This work validates and builds upon previous studies of surfactant performance, wettability alteration, and IFT while providing new insight into nonionic surfactant blends at temperature conditions not currently available in the literature. It also serves as a template for the surfactant screening and selection process when considering nonionic surfactants.

Development of Linagliptin Ultra Fine Solid Supersaturated Bio-SNEDDS Using Triangular Mixture Design for Enhancement of Oral Bioavailability: Impact of P-gp Inhibition

Linagliptin (LIN) is a newly developed dipeptidyl peptidase 4 (DPP-4) inhibitor oral antidiabetic drug. LIN is considered a P-gp substrate, thus suffers from poor bioavailability (&lt; 30%). The aim of this study was to develop and characterize LIN bioactive self-nanoemulsifying drug delivery system to circumvent its poor bioavailability and enhance its therapeutic efficacy.&#x0D; Methodology: In this study, we developed solid supersaturated bioactive self-nanoemulsifying drug delivery system (Ss-bio-SNEDDS) of LIN, using clove oil as an oil phase, cremophor CO 40 as a surfactant, labrasol as a co-surfactant and Hydroxy-propyl-B-cyclodextrin (HPBCD) as a precipitation inhibitor (PI); all components are of established P-gp inhibition activity. Optimization was performed by means of triangular mixture design based on particle size, poly dispersity index (PDI) and percent transmittance. The two optimized formulations (F4 and F8) were designated and evaluated for stability and cloud point. Also, the effect of pH on particle size and PDI was assessed. Additionally, examination of particles’ surface morphology of the two optimized formulations was performed by transmission electron microscope (TEM). The prepared liquid supersaturated-SNEDDS (s-SNEDDS) were converted into solid supersaturated-SNEDDS (Ss-SNEDDS) via adsorption on microcrystalline cellulose (MCC). Further evaluations were carried out, including in vitro drug release, in vitro precipitation and in vivo studies.&#x0D; Results: The optimized formulations F4 and F8 manifested promising characteristics concerning particle size (&lt; 50 nm), PDI (&lt; 0.3) and percent transmittance (&gt; 99%). Stability study showed no phase separation or precipitation with rapid emulsification time. The two optimized formulations showed high cloud point temperature (above 70°C). TEM images of F4 and F8 showed spheroid like appearance with relatively smooth surface. Results of the in vivo study in rats revealed a significant increase in AUC of solid-F4, solid-F8 and solid supersaturated-F4 (S-F4, S-F8 and Ss-F4) by 2.32, 2.89 and 2.54 folds, respectively compared to LIN solution; with a noticeable reduction in blood glucose level at each point.&#x0D; Conclusion: In a nutshell, Ss-bio-SNEDDS are considered as auspicious nano-carriers for LIN with the virtue of augmented bioavailability and possible dose reduction.&#x0D;