Hydrophobic Association Research Articles

3D-printed high-toughness double network hydrogels via digital light processing

Double-network hydrogels have attracted more and more attention in the field of hydrogels due to their high toughness and strength. Up to now, such hydrogels were processed only via model casting and extrusion-based three-dimensional (3D) printing, greatly restricting the freedom of design and manufacture. Herein, we provide a pre-hydrogel ink material composed of commercially available compounds, such as acrylamide and stearyl methacrylate, which can not only be suitable for vat photopolymerization, but also produces a hydrogel with double-network structures. Various hydrogel objects can be printed with a good CAD fidelity, verifying the good printability of the ink material. The printed hydrogels are based on an interpenetrated polymeric network consisting of covalent bond and hydrophobic association, enabling excellent toughness, puncture resistance, and self-recovering performance of the printed objects. The proposed approach may provide an effective way to design the ink of double-network hydrogels suitable for photocurable 3D printing, which may have great application prospects in the fields of customizing wearable sensors, robotics and biomedicine.

Influence of Temperature and Salt Concentration on the Hydrophobic Interactions of Adamantane and Hexane

One of the definitions of hydrophobic interactions is the aggregation of nonpolar particles in a polar solvent, such as water. While this phenomenon appears to be very simple, it is crucial for many complex processes, such as protein folding, to take place. In this work, the hydrophobic association of adamantane and hexane at various temperatures and ionic strengths was studied using molecular dynamics simulations with the AMBER 16.0 program and the GAFF force field. The potentials of mean force of hydrophobic dimer formation, as well as the excess free energy, excess energy, excess entropy, and excess heat capacity corresponding to the formation of the contact minimum, were determined and analyzed. For both systems, the depth of the contact minimum in the potential of mean force was found to increase with both temperature and ionic strength. The excess heat capacity of the association at the contact minimum and T = 298 K was found to be negative and to decrease, while the excess entropy and energy were found to be positive and to increase for both systems, the changes being more pronounced for the hexane dimer. The excess heat capacity is also greater in absolute value for the hexane dimer.

Synthesis and characterisation of a novel pH-sensitive flocculant and its flocculation performance

In this study, a novel pH-sensitive flocculant, poly(AM-DEA-DPL) (PADD), was synthesised using acrylamide (AM), diethylaminoethyl methacrylate (DEA), and dodecyl glucoside (DPL) as monomers through solution copolymerisation. The synthesis conditions were optimised, and the intrinsic viscosity and conversion rate of the polymer were improved. The molecular structure of the flocculant was determined through Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (1H NMR) spectroscopy analysis. The isoelectric points of PADD were found to be pH 4 through zeta potential measurements, indicating that PADD is an amphoteric flocculant. The change in turbidity with pH reflected the pH sensitivity and the change in the hydrophilicity and hydrophobicity of the polymer. Gel permeation chromatography (GPC) measurements showed that the average molecular weight of the polymer was 89,310. PADD had great turbidity removal and flocculation effects on both hydrophilic kaolin and hydrophobic molybdenite. At pH 2–8, a small amount of flocculant had excellent flocculation effects on kaolin and molybdenite suspensions. According to FTIR characterisation and zeta potential measurements of the flocs, and to previous reports, this was mainly the result of electrostatic attraction, adsorption bridging, hydrophobic association, and synergy. The PADD flocculant has promising industrial applications.

The injection method of a hydrophobic associated polymer with evident salt thickening property

A comb like micro-blocked hydrophobic association polymer (CBHAP) with evident thickening property in high salinity and weak thickening property in fresh water was developed. Based on the unique property, we designed the injection strategy that polymer in fresh water with low viscosity was injected into the cores to improve injectivity and high salinity water was used to perform subsequent water flooding to improve mobility control ability. The factors influencing on the injectivity as well as mobility control ability were researched by the core flooding experiments. As a result, pressure fluctuation was found in the subsequent water flooding from 0.7 PV to 1.5 PV, showing obvious variation of viscosity in the cores. The phenomenon was believed to improve mobility control ability. In addition, the positive correlation between polymer concentration, salinity, injected volume and the fluctuation was found. The designed injection method for the polymer can be used to solve injectivity issue as well as improve mobility control ability in high salinity reservoir.

Hydrophobic association and solvation of neopentane in urea, TMAO and urea-TMAO solutions.

A detailed knowledge of hydrophobic association and solvation is crucial for understanding the con-formational stability of proteins and polymers in osmolyte solutions. Using molecular dynamics simulations, it is found that the hydrophobic association of neopentane molecules is greater in a mixed urea-TMAO-water solution in comparison to that in 8 M urea solution, 4 M TMAO solution and neat water. The neopentane association in urea solution is greater than that in TMAO solution or neat water. We find the association is even less in TMAO solution than pure water. From free energy calculations, it is revealed that the neopentane sized cavity creation in mixed urea-TMAO-water is most unfavorable and that causes the highest hydrophobic association. The cavity formation in urea solution is either more unfavorable or comparable to that in TMAO solution. Importantly, it is found that the population of neopentane-neopentane contact pair and the free energy contribution for the cavity formation step in TMAO solution are very sensitive towards the choice of TMAO force-fields. A careful construction of TMAO force-fields is important for studying the hydrophobic association. Interestingly it is observed that the total solute-solvent dispersion interaction energy contribution is always the most favorable in mixed urea-TMAO-water. The magnitude of this interaction energy is greater in urea solution relative to TMAO solution for two different force-fields of TMAO, whereas the lowest value is obtained in pure water. It is revealed that the extent of the overall hydrophobic association in osmolyte solutions is mainly governed by the cavity creation step and it nullifies the contribution coming from the solute-solvent interaction contribution.

Synthesis of a hydrophobic associating polymer and its application in plugging spacer fluid.

The high temperature of formation and multiple stages of leakage zone seriously affect the efficiency and safety of drilling and cementing operations. To improve leakage plugging quality before the cementing process, the hydrophobic associating polymer PHAAO was synthesized from acrylamide (AM), 2-acrylamide-2-methyl propane sulfonic acid (AMPS), and the long side-chain hydrophobic monomer octadecyl dimethyl allyl ammonium chloride (ODAAC) in this study. The structure and molecular weight of the polymer were characterized, and it was proved that the polymer has strong association properties and excellent heat resistance. Utilizing the bridge plugging principle, the polymer PHAAO was used with 36-mesh walnut shells and lignin fiber to form a compound plugging agent. This agent was added to spacer fluid to become a plugging spacer. API water loss tests and loading capacity tests under high temperatures show that the filter cake formed by the spacer fluid is dense. The sealing pressure of the spacer fluid on a 1 mm crack can reach 6.5 MPa at 160 °C, and it has good compatibility with cement slurry. A scanning electron microscopy (SEM) test was conducted to explore the membrane formation mechanism of the polymer. An ultra-low permeability membrane is formed on the surface of the filter cake from the spacer fluid due to the hydrophobic association and hydrogen bonding between the polymer and lignin fiber, thereby greatly reducing the loss of spacer fluid.

A Review on Synthesis Methods of Phyllosilicate- and Graphene-Filled Composite Hydrogels

This review discusses, in brief, the various synthetic methods of two widely-used nanofillers; phyllosilicate and graphene. Both are 2D fillers introduced into hydrogel matrices to achieve mechanical robustness and water uptake behavior. Both the fillers are inserted by physical and chemical gelation methods where most of the chemical gelation, i.e., covalent approaches, results in better physical properties compared to their physical gels. Physical gels occur due to supramolecular assembly, van der Waals interactions, electrostatic interactions, hydrophobic associations, and H-bonding. For chemical gelation, in situ radical triggered gelation mostly occurs.

Tough and self-healing hydrogels based on transient crosslinking by nanoparticles.

In this investigation, transient crosslinking was constructed to obtain a hydrogel with excellent mechanical and self-healing properties. Firstly, core-shell particles with hydrophilic amino groups were prepared by emulsion polymerization and subsequently dispersed into hydrophobic association polyacrylamide hydrogels. Transient crosslinking was constructed through hydrogen bonding between core-shell particles and polyacrylamide. As a result, the hydrogels exhibited a tensile strength of 1.4 MPa and self-healing efficiency of 98% at 24 h. Furthermore, reconstruction of the transient crosslinking was confirmed from rheological measurements. Therefore, the essential reinforcement principle based on transient crosslinking would open a novel strategy to obtain hydrogels with superior toughness and self-healing properties.

Hydrophobic association and ionic coordination dual crossed‐linked conductive hydrogels with self‐adhesive and self‐healing virtues for conformal strain sensors

AbstractAs a promising functional material, conductive hydrogel has attracted extensive attention, especially in flexible sensor field. Despite the recent developments, current hydrogels still experience several issues, such as limited stretchability, lack of self‐recovery and self‐healing capability, and insufficient self‐adhesion. Herein, dual cross‐linked (DC) poly (AA‐co‐LMA)SDS/Fe3+ hydrogels are fabricated subtly on the basis of ionic coordination interactions and the poly (AA‐co‐LMA)SDS hydrophobic association networks, which may provide one plausible routine to compensate the mentioned drawback of hydrogels. The hydrophobic association and ionic coordination networks work synergistically to endow the hydrogels remarkable stretchability (>1200%), high‐fracture strength (≈ 820 kPa), and excellent self‐healing capability. In addition, the DC hydrogel‐based strain sensors displayed a broad sensing range (0 ∼ 900%), conspicuous sensitivity (strain 0% ∼ 200%, gauge factor = 0.53; strain 200% ∼ 500%, gauge factor = 1.23; strain 500% ∼ 900%, gauge factor = 2.09), and pronounced durability. What's more, the self‐adhesive feature ensures the strain sensor always forming a good conformal contact with the skin during human movements and displaying remarkable bidirectional detection capability.

A quinoline alkaloid potentially modulates the amyloidogenic structural transitions of the biofilm scaffolding small basic protein

Bacterial biofilm formation by communities of opportunistic bacterial pathogens like Staphylococcus epidermidis is regarded as the primary virulence mechanism facilitating the spread of detrimental nosocomial and implant-associated infections. An 18-kDa small basic protein (Sbp) and its amyloid fibrils account for strengthening the biofilm architecture and scaffolding the S. epidermidis biofilm matrix. Our study reports systematic analysis of the amyloidogenic structural transitions of Sbp and predicts the amyloid core of the protein which may trigger misfolding and aggregation. Herein, we report the novel amyloid inhibitory potential of Camptothecin, a quinoline alkaloid which binds stably to Sbp monomers and redirects the formation of unstructured regions further destabilizing the protein. Molecular dynamics simulations reveal that Camptothecin averts β-sheet transitions, interrupts with electrostatic interactions and disrupts the intermolecular hydrophobic associations between the exposed hydrophobic amyloidogenic regions of Sbp. Collectively, our study puts forward the first report detailing the heteromolecular associations and amyloid modulatory effects of Camptothecin which may serve as a structural scaffold for the tailored designing of novel drugs targeting the S. epidermidis biofilm matrix. Communicated by Ramaswamy H. Sarma

Synthesis of a hydrophobic association polymer with an inner salt structure for fracture fluid with ultra-high-salinity water

This study used a compound initiation free radical polymerization process to synthesize a hydrophobic association polymer (PDMA1) with good salt resistance for use in ultra-high salinity reservoirs. The critical association and entanglement concentrations of PDMA1 in deionized (DI) water were 1596 and 2799 mg/L, respectively. The properties of the polymer in simulated formation (SF) water were investigated using viscosity change and conductivity tests, and the apparent viscosity of the PDMA1 solution was investigated using apparent viscosity, viscoelasticity, and thixotropy experiments. To a certain extent, the apparent viscosity of the solution was found to be influenced by metal ions. Under total dissolved solids (TDS) concentrations of up to 239,500 ppm, when the polymer concentration exceeded the critical entanglement concentration, the apparent viscosity of the polymer remained close to that of DI water. Additionally, the viscosity of the PDMA1 solution was affected by different types of metal ions, and the polymer solution thickened owing to divalent cations. PDMA1 is resistant to salt owing to hydrophobic interaction, electrostatic shielding, and double-layer compression. The results of the thixotropy and viscoelasticity tests revealed the thixotropy loop area of the PDMA1 solution in SF water to be greater than that in DI water. Under these conditions, PDMA1 is mostly viscous at low shear frequencies and mostly elastic at high shear frequencies. The PDMA1 inner-salt hydrophobic association polymer can be utilized as a chemical agent for tertiary recovery and fracturing, processes in high-salinity reservoirs, particularly for aggravating fracturing fluid.

Improving the mechanical performance of P(N‐hydroxymethyl acrylamide/acrylic acid/2‐acrylamido‐2‐methylpropanesulfonic acid) hydrogel via hydrophobic modified nanosilica

AbstractHydrogels with high mechanical strength are essential for its most industrial applications. In this work, the hydrophobic SiO2nanoparticles (M‐SiO2NPs) modified with octadecyltrimethoxysilane were used as physical crosslinker to toughen the mechanical properties of hydrogels. The solution of monomers containing M‐SiO2NPs, N‐hydroxymethyl acrylamide (NHAM), acrylic acid (AA), 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS), was polymerized to prepare a P(NHAM/AA/AMPS)‐based composite hydrogel without any chemical cross‐linker. The composition and microstructure of the hydrogel were carefully studied with Fourier transform infrared spectroscopy and scanning electron microscopy. The mechanical properties of the hydrogel were investigated through compressive and tensile tests. Dynamic swelling tests were carried out at different pH values (1.0–12.0) and salinity (2000–20,000 mg/L) to study the acid resistance, alkali resistance, and salt resistance of the hydrogel. The obtained results showed that the hydrogel exhibited excellent mechanical performance, which was attributed to the unique 3D network formed by the hydrogen bond between M‐SiO2NPs and polymer as well as the hydrophobic association effect between the hydrophobic chains of M‐SiO2NPs. Furthermore, the hydrophobic association effect was enhanced when contacting with salt, acid, and alkali solutions, thus endowing the hydrogel with intensified salt resistance and wider acid–base adaptability range.

One-step self-assembly for fabricating dual responsive fluorescent aggregates

The fluorescent functional material with dual responsiveness was prepared by combining a cationic surfactant, ferrocene azine (FcA) and dye molecule Congo red (CR) via π-π stacking interaction at the oil-water interface. The resulting binary complex spontaneously organized into flower structure and exhibited double stimuli-response behavior triggered by redox species and pH value. The switching mechanism of aggregates was found to be controlled by the cooperative binding of noncovalent interactions, including π-π stacking and amphiphilic hydrophobic association. The self-assembly mechanism was studied in detail by quantum chemistry simulation. In addition, the aggregates could be used as fluorescent probe for detection of Cu2+. In the presence of Cu2+, the fluorescence enhancement was observed. This novel fluorescent probe based on interfacial self-assembly provides a new strategy for environmental monitoring.

The Synthesis of Associative Copolymers with Both Amphoteric and Hydrophobic Groups and the Effect of the Degree of Association on the Instability of Emulsions.

The acrylamide (AM)/methacryloyl ethyl sulfobetaine (SPE)/behenyl polyoxyethylene ether methacrylate (BEM) terpolymer (PASB) was synthesized by soap-free emulsion polymerization. Four types of PASBs were synthesized by adjusting the moles of AM and BEM with constant total moles of monomers. The synthesized copolymers were characterized by Fourier-transform infrared spectroscopy, thermogravimetry, molecular weight, and viscosity. By measuring the microscopic morphology and backscattered light intensity of the emulsions, the instability process of the emulsions prepared by PASBs was investigated in detail. The main instability processes of the emulsions prepared from PASBs within 45 min were flocculation and coalescence. The intermolecular association of copolymer PASBs was dominated by the behenyl functional groups on the molecular chains. The stability of the emulsions, which were prepared from isoviscosity aqueous solutions controlled by the concentration of the associative copolymers, was increased with the degree of association of copolymers. The hydrophobic association between the copolymer molecules can further slow down the flocculation and coalescence of the emulsion droplets on the basis of the same aqueous solution viscosity, which is one of the reasons for improving the stability of the emulsion.

Evaluation of new hydrophobic association inorganic composite material as coagulant for oilfield wastewater treatment

• The hydrophobic association PASS was prepared by a base titration method. • PASS with a small amount of lipophilic group could be improving charge neutralization ability. • The crude water containing polymer was effectively treated. • Floc properties were comparatively investigated. The use of oil recovery technologies has resulted in the weakening of interfacial tension between oil and water in oilfield wastewater due to a large amount of polymer present. This leads to the formation of stable emulsified colloidal systems and increases the difficulty of oilfield wastewater treatment. This study investigated hydrophobically-modified polyaluminium silicate sulphate (PASS-C) as a coagulant for oilfield wastewater treatment. PASS-C was prepared by the condensation polymerisation of Al 2 (SO 4 ) 3 ·18H 2 O with dialysed and hydrolysed KH570 [3-(trimethoxysilyl)propyl methacrylate] under titration with NaAlO 2 and water glass at low temperature. The zeta potential of PASS-C showed that the introduction of hydrophobic groups increased its charge neutralisation ability. Additionally, compared with conventional PASS, PASS-C showed a satisfactory oil removal rate from simulated polymer flooding oily wastewater. When the hydrophobic group content was 1% and the dosage of PASS-C was 140 mg·L –1 , the optimal oil removal rate and turbidity removal rate was 95% and 98%, respectively. The particle size and morphology of the coagulated flocs were characterised by laser particle size analysis and SEM. Compared with PASS, PASS-C formed a larger and more compact floc. These findings indicated that the good flocculability of PASS-C for crude oil wastewater was attributable to the synergistic effects of charge neutralisation, hydrophobic associations and adsorption bridging.

Hydrophobically Modified Alginate Derivatives via the Ugi Multicomponent Reaction for the Development of Hydrophobic Pharmaceutical Formulations

AbstractIn this work, the hydrophobically modified alginate derivative (HMAD) was synthesized by using sodium alginate, cyclohexyl isocyanide, octylamine and propionaldehyde instead of formaldehyde, based on previous explorations of the Ugi reaction for the modification of alginate. Experimental results revealed that the successful grafting of the hydrophobic chains onto the alginate molecular backbone via the Ugi reaction had weakened and destroyed the intramolecular hydrogen bonds, thus enhancing the molecular flexibility of alginate, which endowed the HMAD with good amphiphilic property with the critical aggregation concentration (CAC) of 0.44 g/L. Moreover, the resultant HMAD could form the stable self‐aggregated micelles with the spherical shape due to the intra or intermolecular hydrophobic associations. Its average hydrodynamic diameter and zeta potential were 458 nm (PDI=0.26) and −61.4 mV, respectively, which was able to achieve the loading and sustained‐release of hydrophobic ibuprofen. Meanwhile, HMAD had no significant cytotoxicity to the murine macrophage RAW264.7 cells. Based on the above merits, the synthesized HMAD could exhibit great potential for the development of hydrophobic pharmaceutical formulations.

Synthesis and properties of temperature-tolerance resistant hydrophobically associating polymer suspension agent using response surface method

Aiming at the problem that the oil well cement slurry is easy to settle and lose its stability under high temperature environment, and combining with the characteristics of traditional cement admixtures "thickening at low temperature and thinning at high temperature", we developed a kind of high-temperature resistant cement suspension agent. A quadripolymer suspension agent P-AN18 was synthesized by free radical polymerization using 2-Acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamide (AM), quaternary ammonium salt monomer N-N octadecyl dimethyl allyl ammonium chloride (DMAAC-18), and high-temperature resistant monomer N-Vinyl-2-Pyrrolidinone (NVP). The synthesis conditions were optimized using the response surface method (RSM) innovatively, the response surface graph (3D) showed the influence of independent variables on the rheological properties and density difference of cement slurry influence. The hydrophobic association structure and high-temperature resistance mechanism of P-AN18 were analyzed by infrared spectroscopy, nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), nanoparticle size analyzer, fluorescence probe test and scanning electron microscope (SEM) in a freezing environment. The effect of P-AN18 on maintaining the stability of cement slurry system at high temperature was evaluated. The results showed that the polymer suspension P-AN18 has good temperature resistance and compatibility with cement slurry. At 200 ℃, P-AN18 can keep the cement slurry system stable, and the density difference between the upper and lower part of the solidified cement column is less than 0.01 g/cm 3 . P-AN18 provides a new method for controlling the settlement stability of high-temperature cement slurry, which is expected to be used to improve the safety and cementing quality of deep well cementing. • Predicting density contrast using RSM model. • Characterizing Polymer suspensions from macro and micro perspectives. • Effective prevention of thermal thinning and particle settling of cement slurry.

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.