Hydrophobic Association Research Articles

Synthesis and properties of hydrophobically associating polymer fracturing fluid

The double tailed hydrophobic monomer PMB-16 was synthesized by the reaction of phenylethylamine,1-bromohexadecane and methacryloyl chloride. The ternary hydrophobic association polymer (PADM) was synthesized by free radical copolymerization of PMB-16 with acrylamide (AM) and methacryloyloxyethyl trimethylammonium chloride (DMC). The optimum synthesis conditions were as follows, the mass ratio of m (AM):m (DMC):m (PMB-16) was 80:19.6:0.4, the total monomer concentration was 35.0 wt%, the amount of initiator (V50) was 0.1 wt% of the total mass of monomer, the reaction temperature was 55 °C, the reaction time was 6.0 h, the system pH was 7, and the amount of metal ion chelating agent (EDTA-4Na) was 0.01 wt% of the total mass of monomer. The results of performance evaluation showed that PADM aqueous solution had excellent temperature and salt resistance. Using zirconium acetylacetonate as crosslinking agent, the mass crosslinking ratio of PADM solution to zirconium acetylacetonate was 100:0.9, the crosslinking temperature was 60 °C, and the pH value was 6.0. The system presented good thickening, temperature resistance, shear stability and low residue content, so it was a low damage fracturing fluid.

Esterification of Alginate with Alkyl Bromides of Different Carbon Chain Lengths via the Bimolecular Nucleophilic Substitution Reaction: Synthesis, Characterization, and Controlled Release Performance.

To extend the alginate applicability for the sustained release of hydrophobic medicine in drug delivery systems, the alkyl alginate ester derivative (AAD), including hexyl alginate ester derivative (HAD), octyl alginate ester derivative (OAD), decyl alginate ester derivative (DAD), and lauryl alginate ester derivative (LAD), were synthesized using the alkyl bromides with different lengths of carbon chain as the hydrophobic modifiers under homogeneous conditions via the bimolecular nucleophilic substitution (SN2) reaction. Experimental results revealed that the successful grafting of the hydrophobic alkyl groups onto the alginate molecular backbone via the SN2 reaction had weakened and destroyed the intramolecular hydrogen bonds, thus enhancing the molecular flexibility of the alginate, which endowed the AAD with a good amphiphilic property and a critical aggregation concentration (CAC) of 0.48~0.0068 g/L. Therefore, the resultant AAD could form stable spherical self-aggregated micelles with the average hydrodynamic diameter of 285.3~180.5 nm and zeta potential at approximately −44.8~−34.4 mV due to the intra or intermolecular hydrophobic associations. With the increase of the carbon chain length of the hydrophobic side groups, the AAD was more prone to self-aggregation, and therefore was able to achieve the loading and sustained release of hydrophobic ibuprofen. Additionally, the swelling and degradation of AAD microcapsules and the diffusion of the loaded drug jointly controlled the release rate of ibuprofen. Meanwhile, the AAD also displayed low cytotoxicity to the murine macrophage RAW264.7 cells. Thanks to the good amphiphilic property, colloidal interface activity, hydrophobic drug-loading performance, and cytocompatibility, the synthesized AAD exhibited a great potential for the development of hydrophobic pharmaceutical formulations.

Zinc Recovery from Wulagen Sulfide Flotation Plant Tail by Applying Ether Amine Organic Collectors.

Separating oxidized zinc minerals from flotation tailings is always a challenge. In this study, a flotation tailing from Wulagen zinc mine in China (Zn grade < 1%) was processed using froth flotation with combinations of amines (OPA 10, OPA 1214, OPA 13, DDA) and Na2S to study the effects of these amines on the zinc recovery as well as their interactions with other reagents, aiming to screen out a proper reagent scheme to improve zinc separation from extremely low-grade zinc flotation tailings. The results show that different amines led to different flotation performance, and the collectors were ranked as OPA 1214, OPA 13, OPA 10 and DDA in a decreasing order based on flotation collectivity and selectivity. An increase in the concentration of each collector increased the zinc recovery but reduced the concentrate zinc grade. Interactions were also observed between different amines and Na2S and Na2SiO3, and OPA 1214 outdid the others in saving the usage of both the Na2S and Na2SiO3. The measured adsorption of collector onto smithsonite was found to correlate well with flotation test results. It was concluded that hydrocarbon chains can be held accountable for the difference in the flotation performance with different amines. The longer the hydrocarbon chain, the stronger the hydrophobic association ability of amine, which is conducive to the selective amine adsorption onto sulfurized smithsonite particles and hence the smithsonite flotation.

A novel hydrophobically associating polymer based on Twin-tailed amphiphilic Monomer: Experimental study and molecular dynamics simulation

A novel twin-tailed amphiphilic monomer named CGS-12 was synthesized. The copolymer GHPAM was prepared by copolymerization of CGS-12 with acrylamide (AM) and acrylic acid (AA) by photoinitiated free radical polymerization in aqueous solution. The critical micelle concentration of CGS-12 is 1.02 × 10-4 M. The rheological behaviour of the above copolymer was studied. It was found that GHPAM provides better performance at high temperature, exhibits unusual salinity sensitivity and tolerates greater higher shear forces. The viscoelasticity and micro morphologies have been investigated revealing that CGS-12 considerably enhances the crosslinking density and promotes to form a more compact network than the corresponding single-tailed hydrophobic monomer DM-12. Finally, we prove via molecular dynamics simulations that CGS-12 can enhance the hydrophobic association compared to DM-12 while maintaining the same hydrophobic chains content, resulting in improved rheological properties.

Molecular interaction of poly (acrylamide‐co‐2‐acrylamido‐dodecyl sulfonate) with dual responsiveness and application in oily emulsion wastewater

AbstractStimuli‐sensitive polymers are a class of macromolecular system with “intelligent” behavior. Herein, a copolymer of poly (acrylamide‐co‐2‐acrylamido‐dodecyl sulfonate), which has salt‐sensitive and thermosensitive properties, is synthesized via precipitation polymerization. Its aqueous solution exhibits a clear sol state, while a gel is obtained via salt‐induction by addition a certain amount of NaCl. More interestingly, the gel can transform into clear sol again upon heating, which exhibits a phase transition of upper critical solution temperature in NaCl solution. The dual responsive behaviors of copolymer solutions are studied via rheological measurements. Then fluorescence spectrum, zeta potential test, and dynamic light scattering are employed to investigate molecular interaction in aqueous solution under varying conditions. It is found that dual responsive behaviors are caused by electrostatic interaction and hydrophobic association. At last, oily emulsion wastewater treatment indicates that this polymer shows characteristics of “smart flocculant” and has potential application prospect.

Water: An underappreciated reaction medium for photodimerizations

Organic solvents have been the sought-after medium to achieve light initiated transformations in laboratories and industries. Given the current emphasis on green chemistry and rising awareness of environmental pollution it may be necessary for us to utilize abundantly freely available, non-toxic and environmentally friendly water as the medium to perform photoreactions. Although water has attracted the attention of organic synthetic chemists, it is yet to receive the indispensable attention of photochemists. In this article we present examples of photocycloaddition reactions of four molecules namely coumarin, indene, cinnamic acid and acenaphthylene that are sparingly soluble in water. Photodimerization of these molecules in water is much faster and occurs at much lower concentrations than in organic solvents. Aggregation probably forced by hydrophobic association is suggested to be the cause for the increased reactivity even at lower concentrations. The dimer distribution in water is different from that in organic solvents. Further work is required to fully understand the mechanism of photodimerization in water. Although the poor solubility of organic molecules in water requires one to irradiate large volumes to collect enough useful amounts, availability of flow reactors and LEDs as light sources should help one overcome the challenges.

Synthesis of Poly(ε-caprolactone) Diacrylate for Micelle-Cross-Linked Sodium AMPS Hydrogel for Use as Controlled Drug Delivery Wound Dressing.

This study focuses on the synthesis of poly(ε-caprolactone) diacrylate (PCLDA) for the fabrication of micelle-cross-linked sodium AMPS wound dressing hydrogels. The novel synthetic approach of PCLDA is functionalizing a PCL diol with acrylic acid. The influences of varying the PCL diol/AA molar ratio and temperature on the suitable conditions for the synthesis of PCLDA are discussed. The hydrogel was synthesized through micellar copolymerization of sodium 2-acrylamido-2-methylpropane sulfonate (Na-AMPS) as a basic monomer and PCLDA as a hydrophobic association monomer. In this study, an attempt was made to develop new hydrogel wound dressings meant for the release of antibacterial drugs (ciprofloxacin and silver sulfadiazine). The chemical structures, morphology, porosity, and water interaction of the hydrogels were characterized. The hydrogels' swelling ratio and water vapor transmission rate (WVTR) showed a high swelling capacity (4688-10753%) and good WVTR (approximately 2000 g·m-2·day-1), which can be controlled through variation of the PCLDA concentration. The mechanical property results confirmed that PCLDA improved the mechanical properties of the hydrogel; the stress increased from 37 to 68 kPa, and the strain increased from 198 to 360% with increasing PCLDA (0-30% wt of Na-AMPS). These hydrogels presented no cytotoxicity based on over 70% cell viability responses (L929 fibroblasts) using an in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Additionally, the drug release mechanism, kinetic models, and antibacterial activity were determined. The results demonstrated that antibiotics were released from the hydrogel with a Fickian diffusion mechanism and antibacterial activity against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus). Based on the results obtained, and bearing in mind that further progress still needs to be made, the fabricated hydrogels show considerable potential for meeting the stringent property requirements of hydrogel wound dressings.

Application of environmentally friendly amphoteric polyacrylamide hydrophobically modified with plant oil as additive in water-based drilling fluid

Hydrophobic associating polymers show great potential in formulation of high-performance drilling fluids, due to their hydrophobic associative ability in high-temperature and high-salt conditions. Herein, a novel amphoteric polyacrylamide of poly(acrylamide/2-acrylamido-2-methyl-1-propanesulfonic acid/methylacrylethyl trimethylammonium chloride) hydrophobically modified with epoxidized soybean oil denoted as PAADE was prepared and applied in water-based drilling fluid, and one without hydrophobic modification (PAAD) was also used for comparison. Compared with PAAD, PAADE displayed characteristic association behavior with a critical association concentration (CAC) of 0.3 w/v%, and a salt thickening phenomenon over 3 w/v% NaCl concentration. The impacts of PAADE and PAAD on rheological and filtration properties of bentonite-based drilling fluid (BTDF) were evaluated under different salinity. The fitted Herschel-Bulkley rheological parameters indicated that BTDF containing PAADE showed stronger yield stress, easier flowability and better salt resistance at a reasonable concentration below CAC. Meanwhile, PAADE largely reduced the fluid loss of BTDF before and after thermal aging at 150°C, showing high temperature tolerance. The addition of NaCl promoted larger reduction of filtration. The superior properties of PAADE in BTDF were revealed to be the competitive results of salt-induced hydrophobic association and inter-particles configuration transition. Moreover, the incorporation of epoxidized soybean oil improved the biodegradability of PAADE.

Simple Osthole/Nanocarrier Pesticide Efficiently Controls Both Pests and Diseases Fulfilling the Need of Green Production of Strawberry.

The application of botanical pesticides is a good choice in organic agriculture. However, most botanical pesticides have limitations of slow action and short persistence for pest and disease management, which constrain their further application. With the objective of exploring a green pesticide for controlling strawberry pests and diseases simultaneously, a star polymer (SPc) with a low production cost was synthesized as a pesticide nanocarrier through simple reactions. The SPc complexed with osthole quickly through electrostatic interaction and hydrophobic association, which decreased the particle size of osthole down to the nanoscale (17.66 nm). With the help of SPc, more nano-sized osthole was delivered into cytoplasm through endocytosis, leading to the enhanced cytotoxicity against insect cells. As a green botanical pesticide, the control efficacy of the osthole/SPc complex was improved against main strawberry pests (green peach aphid and two-spotted spider mite) and disease (powdery mildew), which fulfilled the need of both pest and disease management in sustainable production of strawberry. Meanwhile, the introduction of SPc not only improved plant-uptake but also decreased the residue of osthole due to the higher degradation rate. Furthermore, the application of the osthole/SPc complex exhibited no influence on the strawberry fruit quality and nontarget predators. To our knowledge, it is the first success to control plant pests and diseases simultaneously for sustainable agriculture by only one pesticidal formulation based on nanoparticle-delivered botanical pesticides.

Structure and Unique Functions of Anisotropic Hydrogels Comprising Uniaxially Aligned Lamellar Bilayers

Abstract In this account, we provide an overview of unique anisotropic hydrogels comprising uniaxially aligned lamellar bilayers embedded in amorphous gel matrix. Owing to their unique structures, the lamellar gels exhibit many unique functions that cannot be obtained from conventional hydrogels featuring amorphous and isotropic structures. For example, the periodical multilayer structure having interlayer spacing of several hundreds of nanometers imparts beautiful structural colors to the gel that respond sensitively to mechanical and chemical stimuli, the water-impermeable nature of the bilayers imparts one-dimensional swelling and diffusion, and the hydrophobic association of the bilayers serves as sacrificial bonds to impart high mechanical strength and toughness during deformation. This work demonstrates the significant potential of hydrogel materials fabricated by introducing anisotropic ordered structures.

Crowding effects on water-mediated hydrophobic interactions.

Understanding the fundamental forces such as hydrophobic interactions in a crowded intracellular environment is necessary to comprehensively decipher the mechanisms of protein folding and biomolecular self-assemblies. The widely accepted entropic depletion view of crowding effects primarily attributes biomolecular compaction to the solvent excluded volume effects exerted by the "inert" crowders, neglecting their soft interactions with the biomolecule. In this study, we examine the effects of chemical nature and soft attractive energy of crowders on the water-mediated hydrophobic interaction between two non-polar neopentane solutes using molecular dynamics simulations. The crowded environment is modeled using dipeptides composed of polar and non-polar amino acids of varying sizes. The results show that amongst the non-polar crowders, Leu2 strengthens the hydrophobic interactions significantly, whereas the polar and small-sized non-polar crowders do not show significant strengthening. Distinct underlying thermodynamic driving forces are illustrated where the small-sized crowders drive hydrophobic interaction via a classic entropic depletion effect and the bulky crowders strengthen it by preferential interaction with the solute. A crossover from energy-stabilized solvent-separated pair to entropy-stabilized contact pair state is observed in the case of bulky non-polar (Leu2) and polar (Lys2) crowders. The influence of solute-crowder energy in affecting the dehydration energy penalty is found to be crucial for determining the neopentane association. The findings demonstrate that along with the entropic (size) effects, the energetic effects also play a crucial role in determining hydrophobic association. The results can be extended and have implications in understanding the impact of protein crowding with varying chemistry in modulating the protein free energy landscapes.

The influence of hydrophobicity on sludge dewatering associated with cationic starch-based flocculants

Coagulation/flocculation is an extensive and effective pretreatment technology for improving the sludge dewaterability. A series of hydrophobically associated cationic starch-based flocculants (CS-DMRs) with different degrees of hydrophobicity but similar charge densities were designed and synthesized. The CS-DMRs exhibited excellent sludge dewatering performance. The dewaterability of sludge increased with the hydrophobicity of the CS-DMRs, and the filter cake moisture content (FCMC) and specific resistance to filtration (SRF) could be reduced from 95.47% and 7.09 × 1012 m/kg to 79.26% and 2.258 × 1012 m/kg, respectively, at a constant pressure of 0.05 MPa after conditioned by the starch-based flocculant with the highest hydrophobicity at its optimal dose. Moreover, due to their amphiphilic structures, CS-DMRs could closely interact with the negatively charged extracellular polymeric substances (EPS), efficiently compress the protein and polysaccharide in EPS, and release the bound water. A second-order polynomial model was proposed according to the phenomenological theory to quantitatively analyze the effect of hydrophobicity in these starch-based flocculants on the sludge dewaterability. The structure–activity relationship was built, and the optimal dose and corresponding FCMC could be theoretically estimated accordingly. The results were in good agreement with the experimental results. The dewatering mechanisms were also discussed in detail on the basis of the changes in the FCMC, SRF, capillary suction time, properties of sludge flocs, compression coefficient, microstructures of sludge cakes, EPS fractions and components, and spatial distributions of the proteins and polysaccharides. In addition to charge neutralization, the hydrophobic association effects of CS-DMRs played an important role in the formation of drainage channels and net-like porous structures in the sludge cake to improve its permeability and filterability. This study thus provided a good understanding of the structural effects of the starch-based flocculants on the sludge dewaterability. The results are greatly beneficial to the fabrication and utilization of environment-friendly and high-performance natural polymeric conditioners for sludge treatment.

Effect of anionic surfactant on the properties of nonionic hydrophobically associating polymer based slick water

A water-soluble nonionic surfactant hydrophobic monomer (AT100) was synthesized by esterification of acryloyl chloride with Triton X-100, after that, a nonionic hydrophobically associating polyacrylamide P(AM-AT100) was synthesized and used as drag reducer. They were characterized by IR and NMR. In fresh water, when the concentration of drag reducer reached 0.3 g·L−1 (so called slick water), the viscosity was 3.86 mm2·s−1 with a drag reduction rate up to 74.7%. After sodium dodecyl sulfate (SDS) was added into the slick water, hydrophobic chains of SDS and hydrophobic units in P(AM-AT100) aggregated and micelles were likely formed, and this process was just like hydrophobic association. The viscosity of the slick water increased significantly, while the drag reduction rate of the mixed system decreased. With SDS concentration at 1.5 g·L−1 and the drag reducer concentration at 0.3 g·L−1, the drag reduction rate was 71.72% and viscosity was 6.25 mm2·s−1, indicating that increasing viscosity had a significantly adverse effect on drag reduction performance. The proppant layup experiment confirmed that the sand-carrying capacity of low-viscosity slick water is limited, so proppant will settle inevitably.

Length Effects of Short Alkyl Side Chains on Phase-Separated Structure and Dynamics of Hydrophobic Association Hydrogels

Length Effects of Short Alkyl Side Chains on Phase-Separated Structure and Dynamics of Hydrophobic Association Hydrogels

Evaluation of hydrophobically associating cationic starch-based flocculants in sludge dewatering

Two series of binary graft cationic starch-based flocculants (CS-DMCs and CS-DMLs) with different hydrophilicity and charge density (CD) were prepared by graft copolymerization of acrylamide with 2-(Methacryloyloxy)-N,N,N-trimethylethanaminium chloride and methacrylic acid 2-(benzyldimethylaminio) ethyl chloride, respectively, on the starch (St) backbone. The sludge dewatering performance of CS-DMCs and CS-DMLs were evaluated and compared based on the changes in filter cake moisture content (FCMC), specific resistance of filtration (SRF), fractions and components of extracellular polymeric substances, and various physiochemical characteristics of sludge flocs and cakes. Increase in CD of the St-based flocculants caused improved sludge dewaterability. Under the similar CD, CS-DML with relatively high hydrophobicity exhibited lower FCMC and SRF, larger and denser sludge flocs, and better permeability of sludge cakes than CS-DMCs due to the synergistic effects of charge neutralization, bridging flocculation and hydrophobic association. Furthermore, a second-order polynomial model on the basis of phenomenological theory was successfully applied to quantitatively evaluate the influences of the two important structural factors of these St-based flocculants, i.e., hydrophobicity and CD, on the sludge dewaterability. The structure–activity relationship of the St-based flocculants in sludge dewatering was obtained according to the theoretic simulation. The dewatering mechanisms was discussed in depth on the basis of the experimental and simulated results; besides, the FCMC and optimal dose can be predicted by the established structure–activity relationship. This current work offered a novel and valuable way to exploit and design of low-cost and high-performance graft natural polymeric flocculants applied in efficient conditioning of sludge.

Effect of hydrophobic association on the flow resistance of polymer solutions

Comprehending the percolation law of polymer solutions in porous media is the basis of effective application of polymer flooding. The solution properties of partially hydrolyzed polyacrylamide (HPAM) and the hydrophobically associating polymer AP-P4 were compared, and the seepage characteristics in porous media were studied. The results showed that HPAM is a viscoelastic fluid dominated by a viscosity modulus. The smaller hydrodynamic size (≥3 µm) and low adsorption capacity (200 µg/g) caused an increase in the resistance factor of HPAM in porous media with the increase in injection velocity. Hydrophobic association greatly improved the solution properties of the polymer, with a stronger apparent viscosity, elastic modulus, hydrodynamic size (≥10 µm), and adsorption capacity (780 µg/g), showing that the viscoelastic fluid properties were dominated by the elastic modulus. The resistance factor of the polymer solution in porous media decreased with the increase in injection velocity.

A Dual Physical Cross‐Linking Strategy to Construct Tough Hydrogels with High Strength, Excellent Fatigue Resistance, and Stretching‐Induced Strengthening Effect

AbstractHydrogels with excellent stiffness, toughness, anti‐fatigue, and self‐recovery properties are regarded as promising water‐containing materials. In this work, a dual physically cross‐linked (DPC) sodium alginate (SA)/poly[acrylamide (AAm)‐acrylic acid (AAc)‐octadecyl methacrylate (OMA)]‐Fe3+ hydrogel is reported, which is constructed by hydrophobic association (HA) and ionic coordination (IC). The optimal DPC hydrogel demonstrates excellent mechanical performance: tensile modulus of 0.65 MPa, tensile strength of 3.31 MPa, elongation at break of 1547%, and toughness of 27.8 MJ m–3. SA/P(AAm‐AAc‐OMA)‐Fe3+ DPC hydrogels also exhibit prominent anti‐fatigue and self‐recovery performance (99.1–109.7% modulus recovery and 90.4–108.9% dissipated energy recovery after resting for 5 min without additional stimuli at ambient temperature) through the reconstruction of reversible physical cross‐linking. Some of the SA/P(AAm‐AAc‐OMA)‐Fe3+ DPC hydrogels even exhibit a stretching‐induced strengthening effect, which is similar to the performance of muscle—“the more training, the more strength.” Hence, the combination of HA and IC will provide an effective approach to design DPC hydrogels with desirable mechanical performances and a longer service life for wider applications of soft materials.

Dual Cross‐Linked Polymethacrylic Acid Hydrogels with Tunable Mechanical Properties and Shape Memory Behavior

AbstractHerein, a series of poly(methacrylic acid) hydrogels are prepared via bulk polymerization of methacrylic acid (MAAc) and grafting of Triton X‐100 (TX‐100). One‐pot and extremely simple chemistry consist of only mixing and subsequently heating of commercially available monomer and surfactant. The polymer chains are interconnected through dual physical cross‐link points formed by the hydrophobic associations in the center of TX‐100 micelles and hydrogen bonds stabilized by hydrophobic α‐methyl groups of MAAc. The hydrogels exhibit tunable mechanical properties ranging between softness and stiffness by adjusting the surfactant/monomer molar ratio, such as Young modulus of 0.6−22 MPa, elongation at break of 750−1700%, tensile strength of 0.21−3.6 MPa, and compressive strength of 41−93 MPa. The synergistic effect of high‐density hydrogen bonds with hydrophobic associations endows a plastic‐like hydrogel with high strength and shape memory (SM) behavior, while a high concentration of micelles with low‐density hydrogen bonds endows a stretchable elastic hydrogel. The combination of temperature‐induced SM property and wide‐ranging mechanical performance will make such hydrogels useful in diverse applications.

Chemically modified phytoglycogen: Physicochemical characterizations and applications to encapsulate curcumin

Phytoglycogen (PG), a water-soluble glycogen-like α-d-glucan, exists as natural dendritic nanoparticles which are known as a promising solubility enhancer and delivery vehicle for lipophilic compounds. However, the practical applications of PG in food and pharmaceutical fields are limited by their high hydrophilicity and relatively low encapsulation efficiency compared with other delivery systems. The objectives of this work were to chemically modify native PG nanoparticles with hydrophobic groups and to characterize their physicochemical properties, as well as to evaluate the application feasibility of modified PG (mPG) nanoparticles as a carrier for hydrophobic bioactive compounds. The surface hydroxyl groups of PG nanoparticles were capped with various anhydrides, e.g., acetic, valeric, and N-caprylic, to obtain the PG nanoparticles with different hydrophobicity. Successful modification by acyl groups was evidenced by both Fourier-transform infrared and nuclear magnetic resonance spectroscopies. The mPG nanoparticles exhibited a more compact structure and homogeneous size distribution as revealed by dynamic light scattering measurement and visualized by transmission electron microscope, while their size slightly increased with the chain length of anhydride. Rheological measurement revealed that the viscosity of mPG at low shear rate was increased with the increase of degree of substitution due to the intermolecular hydrophobic association. A novel pH-driven method to load curcumin showed significantly higher encapsulation efficiency and greater antioxidant activity compared with traditional ethanol mediated loading method. Hydrophobic modification of natural dendritic PG nanostructures demonstrates promising potential to develop food-grade nanocarriers for lipophilic bioactive compounds with improved bioactivity.

Tunable mechanical and self-healing poly (acrylic acid-co-stearyl methacrylate) hydrogels induced by soaking methods

Due to the limitation of mechanical properties, the applications of traditional polymer hydrogels are seriously hindered in many fields. In this study, a series of hydrogels with controllable mechanical properties were successfully prepared by immersing the thermo-initiated poly (acrylic acid-co-stearyl methacrylate) hydrogels into LiCl, NaCl and KCl aqueous solution. The structural changes and properties of the gel before and after soaking were explored carefully by XRD, IR and Raman, etc. It was found that except for forming coordination interactions with the carboxyl group of acrylic acid, these salts can also promote the formation of hydrophobic associations consisted of long alkyl chains, which significantly improves the mechanical properties of the gel. The tensile strength and fracture energy of the KCl aqueous solution treated hydrogels could reach to 2.1 MPa and 19 MJ/m3, respectively, which are much higher than those of original hydrogels. Furthermore, the prepared hydrogels also have pressure sensitive conductivity, which could be used to detect body movements.