The rheological properties of partially hydrolyzed polyacrylamide (HPAM) and PEO-PPO-ph-PPO-PEO (BPE) or PPO-PEO-ph-PEO-PPO (BEP) block polyether solutions are investigated here. Another hydrophobically associating polymer (HMPAM) is chosen as a contrast. The rheological results show that the elastic modulus (G′) and viscous modulus (G″) of HPAM/BPE and HPAM/BEP solutions first increase then decrease, while the viscosities of HMPAM/BPE and HMPAM/BEP solutions decrease with the increase of block polyether concentration. The HPAM/BPE solution has a larger viscosity than HPAM/BEP, while the HMPAM/BPE solution has a lower viscosity than HMPAM/BEP. The polymer solutions containing BEP have larger G′ and G″ values than the solutions with BPE. Furthermore, the block polyethers reduce the sensitivity of viscosity to temperature. BEP is more effective to stabilize the viscoelastic property and improve the temperature resistance than BPE in HMPAM system. BEP has a better property to enhance the salt tolerance of the polymer solution than BPE. Moreover, the enhanced oil recovery (EOR) experiments show that HPAM/block polyether mixed solution has a larger oil recovery than HPAM, and HPAM/BEP system has a larger enhanced effect than HPAM/BPE solution.

The dilational rheological properties of hydrophobically modified polyacrylamide (HMPAM) or hydrolyzed polyacrylamide (HPAM) solutions without and with imidazolium surfactants ([C14-4-C14im]Br2 and [C14mim]Br) at the air/water surface were investigated using oscillating bubble measurements. The results obtained suggest that imidazolium surfactants interact with the polymer on the surface, enhancing the dilational viscoelasticity of surface film. The dilational modulus value of [C14-4-C14im]Br2/HMPAM is higher than that of the [C14mim]Br/HMPAM system at low polymer concentration, confirming that [C14-4-C14im]Br2 with two head groups and two hydrophobic chains can combine with a polymer to form a strong film on the surface. Moreover, imidazolium surfactants have stronger hydrophobic interaction with HMPAM chains than those of HPAM, thus enhancing the surface film strength for a surfactant/HMPAM system. The surface interaction mechanism between polyacrylamide and imidazolium surfactant is proposed to result from the electrostatic interactions and the hydrophobic effect.

The aggregation behavior of sodium bis-(2-ethylhexyl)-sulfosuccinate (AOT) at the air/water interface in the absence and presence of inorganic salts was investigated by molecular dynamics simulation. Both monovalent and divalent ions were studied, such as LiCl, NaCl, KCl, MgCl2 and CaCl2. It has been proved that these inorganic ions have great influence on the structure of the AOT monolayer and water molecules around its headgroup. In the presence of inorganic salts, AOT molecules are relatively ordered at the interface and water around the headgroups of AOT shows a lower diffusion coefficient compared with the situation without inorganic salts. All the counterions are prone to move toward the headgroups and locate at the interface. Divalent ions have a strong interaction with AOT, thus they affect the aggregation behavior of AOT remarkably.

The interactions between Pluronic block polyethers (L64 and 17R4) and cetyltrimethyl ammonium bromide (CTAB) were investigated by the measurement of the interfacial dilational viscoelasticity. The dilational moduli of the Pluronic block polyether/CTAB solutions firstly increased, passed through the maximum, and then decreased with the increasing concentration of CTAB. 17R4/CTAB mixed solutions have much larger dilational moduli than L64/CTAB systems, which means that 17R4 and CTAB have stronger interactions than L64 and CTAB. The dilational moduli of 17R4/CTAB systems were different from L64/CTAB systems in the presence of NaBr. The dilational moduli of the L64/CTAB mixed solutions decreased firstly, passed through the minimum value, and then increased with the increasing concentration of NaBr, while the dilational moduli of 17R4/CTAB mixed solutions increased firstly, passed through the maximum, and then decreased. These differences show that NaBr has great influence on the interactions between Pluronic block polyethers and CTAB.

Polyvinyl alcohol (PVA) hydrogels have been proposed for use as promising biomaterials in biomedical and tissue engineering, and graphene oxide (GO) has been recognized as a unique two-dimensional building block for various graphene-based supramolecular architectures. In this article, we systematically studied the influence of three kinds of PVA with different molecular weights on the interaction between PVA and GO. Moreover, the effects of PVA on the gelation of GO were also investigated. The native PVA hydrogel, as well as PVA–GO hybrid hydrogels, have been thoroughly characterized by the phase behavior study and various techniques including field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and rheological measurements. It can be seen that with the increase of the molecular weight of PVA, the addition of GO can effectively promote the gelation of PVA which can be reflected by a decrease of the critical gel concentration (CGC) for PVA–GO hydrogels. Dye adsorption experiments indicate that the toxic dye, i.e., methylene blue (MB), was efficiently entrapped in the PVA–GO xerogels. It is also demonstrated that the gelation of PVA and GO composites can be promoted by different supramolecular interactions, including hydrogen bonding and electrostatic interaction. This work indicates that the PVA–GO composite is a good candidate for preparing “super” and “smart” hydrogels and will enable further studies on the supramolecular chemistry of PVA, graphene and its derivatives.

•The interactions between BSA (or gelation) and NaDC were compared.•The interaction between BSA and NaDC is stronger than that of gelation/NaDC system.•A model of interaction between protein and NaDC has been brought out.•This research might find significant applications in various industrial areas.Surface tension, fluorescence and circular dichroism (CD) methods have been used to investigate the interaction between a biological surfactant sodium deoxycholate (NaDC) and proteins including bovine serum albumin (BSA) and gelatin. It can be seen from the surface tension measurements that both NaDC/BSA and NaDC/gelatin systems can form complexes and the ability of NaDC/BSA to lower surface tension is more obvious than that of NaDC/gelatin. The formation of the complexes influences not only the polarity of the microenvironment of the systems but also their fluorescence spectra. The far-UV CD spectra shows that the α-helical network of BSA increases first and then decreases as the concentration of NaDC increases, while the random coil content of gelatin always increases. A model of interaction between protein and NaDC influenced by the concentration of NaDC has been brought out based on the data gained from this study.Schematic illustrations of the interaction between NaDC and BSA: (A) BSA solution; (B) the interaction between NaDC monomer and BSA; (C) the interaction between NaDC dimer and BSA; (D) the interaction between NaDC secondary aggregate and BSA. The rigid skeleton and carboxyl group of NaDC are respectively represented by an orange semicircle and a negatively charged blue ball.

Silicone surfactants favor spreading at interfaces and siloxane has strong interaction with carbon nanotubes (CNT), thus silicone surfactant may be a good dispersant of CNT. Here, four silicone surfactants (named S1E19, S2E38, S2E16 and S1E16P8) were used to disperse CNT in aqueous solutions. The effects of surfactant structure and concentration on the ability at dispersing CNT were considered. All of the four silicone surfactants can disperse CNT in aqueous solution and the sample with 1,000 mg L−1 S1E16P8 was the best one. The hydrophilic group polyoxyethylene (PEO) and the hydrophobic groups siloxane and polypropylene (PPO) are crucial factors in the ability of dispersing CNT. S2E38 with more ethylene oxide (EO) groups has a stronger ability to disperse CNT than S2E16. The dispersion system provided by S1E19 which contains fewer siloxane and EO groups is relatively unstable and disperses less CNT. These experimental results are explained by molecular dynamics simulation. S2E38 compared with S1E19 and S2E16 has stronger interactions with CNT. The interaction energy of CNT with S1E16P8 which has a PPO moiety but fewer siloxane groups is close to that of S2E16. Furthermore, it can be concluded that these four surfactants are adsorbed on CNT mainly by van der Waals forces and the Si–O–Si chain of silicon surfactant was flexible due to the long Si–C bond and it could easily wrap onto the surface of CNT through hydrophobic and other intermolecular interactions. The hydrophilic part of PEO helped the CNT dispersed in the aqueous solution and prevented CNT from aggregating in water through steric stabilization.

The aggregation behaviors of X-shaped block copolymers, Tetronic 1107 and Tetronic 90R4 with a sequential and reverse architecture, at the air/water interface were studied. The effects of block sequence, concentration, and temperature were investigated by equilibrium surface tension, surface dilational viscoelasticity, and surface tension relaxation measurements. The conformations of Tetronic 1107 and Tetronic 90R4 are different at the air/water interface. The possible adsorption model of Tetronic 1107 is “brush” and that of Tetronic 90R4 is invert “umbrella”. With the increase of temperature, the dilational modulus of Tetronic 1107 solutions decreases, while that of Tetronic 90R4 solutions increases. The mechanisms of the temperature which effects on the conformational transition of Tetronic 1107 and Tetronic 90R4 were discussed in detail. Furthermore, the thermodynamic parameters for the micellization of Tetronic 1107 and Tetronic 90R4 were compared at different temperatures.

•The cross-linkage effect of cellulose/laponite hybrids was investigated.•Rheological measurements demonstrated a sol-to-gel transition triggered by loading of laponite.•The cross-linkage effect of cellulose/laponite hybrids was responsible for tensile strength enhancement of composite films.Homogenous cellulose/laponite aqueous dispersions and composite films were respectively prepared from the pre-cooling NaOH/urea aqueous systems. Rheological measurements of aqueous dispersions demonstrated a sol-to-gel transition triggered by loading of laponite, reflecting a cross-linkage effect of cellulose/laponite hybrids. Similarly, based on scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) characterizations, as well as mechanical and thermal measurements, the cross-linkage effect of cellulose/laponite hybrids was also found in solid films, which played an important role in improving the tensile strength (σb) of composite films. For instance, the σb exhibited a largest enhancement up to 75.7% at a critical laponite content of 0.100 wt%, indicating that the property of composite film was closely related with the dispersion and interaction state of laponite, i.e. its content in cellulose matrix. These results were expected to provide significant information for fabrication and utility of cellulose-based materials.

•We used NaDC and Eu(NO3)3 to prepare luminescent hydrogels.•The hydrogels have excellent gelation capabilities and mechanical strength.•The maximum emission of hydrogel is at 1:3 between Eu(NO3)3 and NaDC.•The incorporation of lanthanide ions imparts versatile functionalities for hydrogels.Luminescent hydrogels were facilely designed through supramolecular self-assembly of biological surfactant (sodium deoxycholate, NaDC) and lanthanide salt (Eu(NO3)3). The microstructures of the hydrogels were characterized by transmission electron microscopy (TEM), high-resolution TEM (HR-TEM) and field emission scanning electron microscopy (FE-SEM), from which nanofibers and tiny particles were observed. The arrangement of the deoxycholate and metal ions was proposed according to small-angle X-ray scattering (SAXS) and X-ray powder diffraction (XRD) measurements. Rheological measurements revealed that the mechanical strength of the hydrogels increased with increasing concentration of NaDC and Eu(NO3)3, while the maximum emission of the fluorescence of the gels appeared at a stoichiometry between Eu(NO3)3 and NaDC of 1:3. It is expected that the incorporation of luminescent lanthanide ions could impart versatile functionalities for practical applications to the hydrogels.Graphical abstract

Supramolecular hydrogels were prepared in the mixtures of biological surfactant sodium deoxycholate (NaDC) and halide salts (NaCl and NaBr) in sodium phosphate buffer. It is very interesting that with the addition of two kinds of amino acids (l-lysine and l-arginine) to NaDC/NaX hydrogels, the gel becomes solution at room temperature. We characterized this performance through phase behavior observation, transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectra, and rheological measurements. The results demonstrate that the gels are formed by intertwined fibrils, which are induced by enormous cycles of NaDC molecules driven by comprehensive noncovalent interactions, especially the hydrogen bonds. Our conclusion is that the presence of halide salts (NaCl and NaBr) enhances the formation of the gels, while the addition of amino acids (l-lysine and l-arginine) could make the breakage of the hydrogen bonds and weaken the formation of the gels. Moreover, its fast disassembly in the presence of amino acids allows for the release of substances (i.e., the dye methylene blue) entrapped within the gel network. The tunable gel morphology, microstructure, mechanical strength, and anisotropy verify the role of halide salts and amino acids in altering the properties of the gels, which can probably be exploited for a variety of applications in future.

The interaction between an ethoxylated alkylphenol polymer with formaldehyde (EAPPF) and a triblock polyEO–polyPO–polyEO copolymer (TBCP) in aqueous solutions has been investigated in detail by means of surface tension, steady-state fluorescence, dynamic light scattering (DLS) measurements and computer simulations. For comparison, the ethoxylated alkylphenol oligomer (EAPO), which is the monomer unit of EAPPF, and another nonionic water-soluble polymer PEG were also selected to get more information about the interaction between different types of surfactants and polymers. The surface properties of mixed systems at the air/water surface were evaluated from surface tension measurements. Information about the hydrophobic microenvironment and size of the aggregates was obtained from steady-state fluorescence using pyrene as a hydrophobic probe and DLS measurements, respectively. The dissipative particle dynamics simulation method was applied to simulate the interaction between EAPPF (or EAPO) and TBCP (or PEG) in aqueous solutions. The synergetic interaction between EAPPF (or EAPO) and TBCP in binary mixed solution enhanced the adsorption of surfactant molecules (EAPPF or EAPO) at the interface, while no obvious interaction between EAPPF (or EAPO) and PEG was observed.

•The foam stability of composite system is better than for either single component.•There exist optimum foaming concentrations for AES and welan gum.•A network structure is formed in the AES/welan gum composite system.•High interfacial elasticity is required to stabilize the interfacial layer.Foam properties of the anionic–nonionic surfactant sodium fatty alcohol polyoxyethylene ether sulfate (AES) and microbial polysaccharide welan gum composite systems have been investigated. Both foaming ability and foam stability of AES/welan gum composite system are better than for either single component. It is important to control the quantities of the two species when to use, since there exist optimum foaming concentrations for AES (1000 mg L−1) and welan gum (80 mg L−1). Competitive adsorption exists between AES and welan gum at the air/liquid interface. A network structure is formed in the AES/welan gum composite system as the dynamic modulus has exponential relationship with the concentration. High interfacial elasticity is required to prevent the coalescence of the bubbles and the rupturing of interfacial layers. The hydrogen bonds and van der Waals forces between AES and welan gum may hinder AES molecules from diffusing from the bulk to the interface. The formation of an interface network of welan gum and the structural stability of double helices, arranged in parallel as zipper model within the network, strengthen the ability of the film to resist disturbance and deformation.

The effect of polymers (hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM)) on the stability of oil-in-water nano-emulsions has been studied in paraffin oil/Span 20-Tween 20/water systems by method of phase inversion composition (PIC). The stabilization of nano-emulsions was investigated by visual observation and the change of water content induced by centrifugation. Droplet size distributions of nano-emulsions were obtained by a laser-scanner particle size distribution analyzer. The interfacial tension and charge of nano-emulsions were obtained by interfacial tension and zeta potential measurements. All the results indicate that the droplet size can be decreased by the addition of HMPAM, while almost no change could be observed when the HPAM was added. Meanwhile, HMPAM has a better effect on the stabilization of nano-emulsions than HPAM. It may conclude that the HMPAM molecules adsorbed at the oil/water interface of the nano-emulsion droplets. Therefore, the stability of nano-emulsion with the addition of HMPAM is based on both an associative thickening mechanism caused by the alkyl chains of HMPAM molecules and the adsorption of HMPAM at the oil/water interface, which can form a solid film to prevent the Ostwald ripening of nano-emulsion droplets.

Rheological properties of welan gum and xanthan gum solutions have been characterized systematically at various concentrations, temperatures and salinities. It is found that the viscoelasticity of welan gum is higher than that of xanthan gum at the same condition though the molecular weight of welan gum is lower. In view of this, welan gum will make a good performance in enhanced oil recovery, especially in high temperature and high salinity reservoirs. Network structure can be formed in solutions of welan gum and xanthan gum for the dynamic modulus has exponential relationship with the concentration. Moreover, the molecular aggregates of welan gum adopt a different arrangement with that of xanthan gum, adjacent double helices of welan gum arrange in parallel as the zipper model. The structure formed by zipper model is still stable in high temperature and high salinity.Highlights► Rheological properties of welan gum and xanthan gum solutions have been compared. ► Welan gum shows a higher viscoelasticity than that of xanthan gum. ► The dynamic modulus has exponential relationship with the concentration. ► Adjacent double helices of welan gum arrange in parallel as the zipper model. ► The network structure formed by zipper model is more stable.

A water-in-oil microemulsion was prepared by using nonionic surfactant Triton X-100, 1-hexanol, cyclohexane and AgNO3 aqueous solution with a concentration of 0.2 mol L−1. Successive addition of sodium borohydride (NaBH4), ammonium hydroxide (NH3·H2O) and tetraethyl orthosilicate (TEOS) to this microemulsion leads to the formation of hierarchically-organized Ag@SiO2 hybrid nanoparticles with Ag nanocrystals randomly distributed inside amorphous SiO2, as proved by transmission electron microscopy (TEM) and high-resolution electron microscopy (HRTEM) observations. In many cases, H2 gas bubbles, which were produced during the reduction of Ag+, were found to influence the structures of Ag nanocrystals. The morphologies of the hybrid nanoparticles and the H2-induced cavities can be easily tuned by the molar ratio of AgNO3 to NaBH4 and the volume ratio of AgNO3 aqueous solution to TEOS. Embedded in amorphous SiO2, the Ag nanoparticles are highly stable, while the unprotected Ag nanocrystals underwent fast aggregation. The inner Ag nanocrystals have dominant (111) planes and are optically active, as shown by X-ray powder diffraction (XRD) and UV-vis measurement, respectively. These properties make these Ag@SiO2 hybrid nanoparticles fascinating candidates for a variety of applications in catalysis and life science.

The influence of Ca2+ on the aggregation of sodium dodecyl sulfate (SDS), sodium dodecyl oxyethylene sulfate (SDES), sodium dodecyl benzene sulfate (SDBS) and sodium dodecyl benzene oxyethylene sulfate (SDBES) at air–water interface were compared to investigate the role of oxyethylene unit by means of the molecular dynamics simulation. In the SDES and SDBES systems, the interaction between OSO3− groups and Na+ions decreases, the diffusion coefficient of Na+ increases, while the interaction between surfactants and Ca2+ ions increases, and the diffusion coefficient of Ca2+ ions decreases. Unlike SDS and SDBS systems, the EO groups introduced may bind Ca2+ ions and the interaction between Ca2+ ions OSO3− groups is weakened, consequently, the precipitation of anionic surfactant by Ca2+ ion is restrained, i.e., the Ca2+-tolerance of anionic surfactants via the introduction of EO groups may be improved. The present results could help in choosing of anionic surfactants used in aqueous solution with inorganic salts.Graphical abstractIn the SDS and SDBS systems, the Ca2+ ions are mostly around the head groups, and tend to precipitate surfactants, while more Ca2+ ions should close to the Op in the SDES and SDBES systems, and only a few Ca2+ ions appear to the head groups, then the surfactants would not precipitate easily, so the Ca2+-tolerances of SDES and SDBES molecules are higher than that of SDS and SDBS molecules.Highlights► Some Ca2+ ions enter into the interface only in the SDES and SDBES systems. ► The appearance of Ca2+ ions decreases the interactions between OSO3− groups and Na+ ions. ► The introduced EO groups can bind Ca2+ ions and restrict the mobility of Ca2+ ions. ► Only a few free Ca2+ ions interact with the head groups for the existence of EO groups. ► The presence of EO groups also increases the hydration ability of OSO3− groups.

The foam properties of Tween 20 and BSA systems in Tris–HCl buffer solution were investigated by nitrogen-blowing method on a Foamscan. The foamability of Tween 20/BSA systems is obviously better than that of individual BSA system. The foams stabilized by BSA drained slower than Tween 20 systems with or without BSA. The foam stability of Tween 20 systems is enhanced by an addition of BSA. The optimal ratio of Tween 20 to BSA is determined for the most stable foams. Surface dilational rheological results indicate surface elasticity dominates the adsorbed layer and it is increased in the presence of BSA. The variation of surface elasticity accords with that of foam stability with an increase of Tween 20 concentration. It can be concluded surface elasticity dominates the corresponding foam stability.Graphical abstractThe formation of gel-like network at the air–water surface distinctly improves the film stability.Highlights► Tween 20–BSA systems have better foamability and foam stability. ► The optimal ratio of Tween 20 to BSA is determined for stable foams. ► Surface elasticity dominates corresponding foam stability. ► Foam stabilization mechanism relies on gel-like networks at air–gas interface.

Oil-in-water (o/w) nano-emulsions with paraffin as an oil phase and Sorbitan monooleate (Span 20)/polyoxyethylene sorbitan monooleate (Tween 20) as emulsifiers were prepared using the emulsion inversion phase (EIP) method at 25 ℃. The properties of the nano-emulsions were investigated in detail as a function of emulsifier content and the addition of ionic surfactants including cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). The droplets of the nano-emulsions become smaller with the increasing concentration of Tween 20/Span 20 and the polydispersity of the droplets decreases. Similarly, the mean droplet size also decreases with the addition of both CTAB and SDS. The zeta potential of the nano-emulsion droplet without SDS or CTAB was found to be negative. Upon the addition of SDS, a more negative value was obtained which leads to an increased electrostatic interactions between droplets and improves the stability of the nano-emulsions via lowering the Ostwald ripening rate. Upon the addition of CTAB, however, a less negative zeta potential was induced which weakens the electrostatic interactions between droplets and lowers the stability of the nano-emulsions. These results indicate that electrostatic interaction is the main factor determining the stability of the nano-emulsions. Interfacial rheological measurements indicated that the maximum values of dilational moduli of both Tween 20/SDS and Tween 20/CTAB mixed adsorption layers at paraffin oil/water interface are lower than that of single adsorption layer of Tween 20. Our results give new insights of the nano-emulsions containing mixed surfactants and may serve as guidelines for preparation of new nano-emulsion systems for practical applications.Graphical abstractWater removal (K, squares) and zeta potential (ζ, circles) as a function of the concentration of mixed emulsifier Span 20/Tween 20.Highlights► We used emulsion inversion phase method to prepare nano-emulsions. ► The stability of the nano-emulsions was enhanced with the addition of SDS. ► SDS and CTAB induce a decreased droplet size but have opposite trends of stability. ► The electrostatic interactions are responsible for the stability of the nano-emulsions. ► This method might find significant applications in various industrial areas.

Nonviral vectors are highly desirable for the development of efficient gene delivery systems. In this study, we report the monomolecular condensation of plasmid DNA and efficient cell transfection by imidazolium gemini surfactants ([C12-4-C12im]Br2), which could be a potential nonviral vector for efficient gene therapy. Homogeneous DNA/[C12-4-C12im]Br2 nanoparticles are formed with a diameter of approximately 100 nm and investigated by using atomic force microscopy. DNA condensates evolve from supercoiled DNA molecules, to individual toroids, to close-packed particles, and eventually to multimolecular aggregates with the increase of [C12-4-C12im]Br2 concentrations. Highly efficient gene transfection in vitro is demonstrated in human embryonic kidney 293 (HEK293) and HeLa cells, which could be attributed to the effective DNA condensation into uniform nanoparticles induced by [C12-4-C12im]Br2. In addition, the low cytotoxicity of [C12-4-C12im]Br2 at transfection concentration region verified by cell viability assay (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide, MTT assay) also supports [C12-4-C12im]Br2 as an effective gene vector. The high gene transfection efficiency by [C12-4-C12im]Br2 as well as its low cytotoxicity could shed light on the rational molecular design of nonviral vectors for gene delivery systems.

The effect of inorganic salts (CaCl2, MgCl2, NaCl, NaI and NaSCN) on the aggregation behavior of a synthesized polyether with seven poly (ethylene oxide)-b-poly (propylene oxide)-b-poly (ethylene oxide) (PEO-PPO-PEO) arms attached to a tetraethylenepentamine core (simplified AE73) at air/water and n-heptane/water interfaces has been investigated by interfacial tension and oscillating bubble methods. The additions of NaCl, CaCl2, and MgCl2 may facilitate the micellization of AE73 and increase its maximum interfacial excess concentration (Γmax) due to the “salting out” effect, while NaSCN induces opposite effect and NaI exerts little influence. The adsorption kinetics of AE73 is controlled not only by the diffusion between the bulk solution and the interfacial layer but also by the energetic and steric barriers generated by the already adsorbed molecules. The adsorption relaxation time of AE73 is reduced with the addition of salts and this phenomenon is more prominent at the n-heptane/water interface. The “salting in” ions decrease the dilational modulus of AE73 while the “salting out” ions induce an opposite effect. The mechanisms of the interaction between inorganic ions and the polyether were discussed; the difference in aggregation behavior between linear and branched block polyethers were also compared.

Calcium carbonate (CaCO3) was crystallized in (2-hydroxypropyl-3-butoxy) propyl-succinyl chitosan (HBP-SCCHS) solutions by a slow vapor diffusion method. The CaCO3 crystals were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetry analysis (TGA) and N2 adsorption–desorption methods. By varying the concentrations of HBP-SCCHS and Ca2+, temperature and initial pH, the CaCO3 crystals with different morphologies were obtained. Based on the analysis of CaCO3 crystals obtained under different conditions, the mechanisms of the CaCO3 crystallization in the presence of HBP-SCCHS were proposed. It was found that the adsorption of HBP-SCCHS molecules on CaCO3 surfaces played a key role in the formation of CaCO3.Typical SEM images of CaCO3 particles obtained from HBP-SCCHS solution. The inset is the magnified SEM image of lenticular-like aggregates after being calcined at 400 °C for 12 h.Highlights► CaCO3 was crystallized in HBP-SCCHS solutions by a slow vapor diffusion method. ► Several influencing factors on the crystallization were investigated. ► The mechanisms of the CaCO3 crystallization in HBP-SCCHS solutions were proposed. ► The work will provide good insight into the CaCO3 crystallization.

To explore the effect of surfactant structure and concentration on the dispersibility of SWNTs in aqueous solutions, the molecular dynamics (MD) simulation was employed to investigate the interactions between the single-walled carbon nanotubes (SWNTs) and four surfactants with and without conjugated structure in water. It is confirmed that surfactants with conjugated structure have a stronger interaction with the SWNT. Aggregate morphologies of surfactants with conjugated structure are different from those without conjugated structure. Multi-layers are prone to form in the former system and the latter one appears semi-micelles on the surface of SWNT. Furthermore, the structures of water and counterion layers around the headgroups are also affected by surfactant structure and concentration. All these changes could present the dispersing ability of surfactants for SWNTs and instruct their applications.Highlights► The interactions between SWNT and surfactants with and without conjugated structure were investigated and compared. ► Different aggregate morphologies on the SWNT were observed. ► The structures of water and counterion layers around the headgroups are affected by surfactant structure and concentration. ► This study could present the dispersing ability of surfactants for SWNTs and instruct their applications.

The block polyethers PEO-PPO-ph-PPO-PEO (BPE) and PPO-PEO-ph-PEO-PPO (BEP) are synthesized by anionic polymerization using bisphenol A as initiator. Compared with Pluronic P123, the aggregation behaviors of BPE and BEP at an air/water interface are investigated by the surface tension and dilational viscoelasticity. The molecular construction can influence the efficiency and effectiveness of block polyethers in decreasing surface tension. BPE has the most efficient ability to decrease surface tension of water among the three block polyethers. The maximum surface excess concentration (Γmax) of BPE is larger than that of BEP or P123. Moreover, the dilational modulus of BPE is almost the same as that of P123, but much larger than that of BEP. The molecular dynamics simulation provides the conformational variations of block polyethers at the air/water interface.

The compaction and condensation of DNA induced by cationic imidazolium gemini surfactants ([Cn-4-Cnim]Br2, n = 10, 12, 14) at different charge ratios have been investigated by dynamic light scattering (DLS), zeta potential, circular dichroism (CD), and ethidium bromide exclusion assay. Upon addition of [Cn-4-Cnim]Br2, DNA molecules undergo the process from compaction to multi-molecular condensation accompanied by conformation change, which could be proved by the DLS and CD results. The charge density changes in zeta potential measurements indicated the impact of the electrostatic interaction in DNA–surfactant complex. The comparison between DNA compaction and condensation by [Cn-4-Cnim]Br2 with different tail lengths demonstrated the important contribution of the hydrophobic interaction. The EtBr exclusion assay indicates the π–π interaction between imidazolium groups of [Cn-4-Cnim]Br2 and DNA aromatic rings also plays a role in the DNA/[Cn-4-Cnim]Br2 complex formation. The impact of the different interactions on the DNA compaction and condensation by gemini surfactants would shed light on their potential applications in gene delivery.Graphical abstractHighlights► An evolution from DNA compaction to multi-molecular DNA condensation induced by [Cn-4-Cnim]Br2 is identified and its mechanism is discussed. ► [Cn-4-Cnim]Br2 as novel imidazolium gemini surfactants can interact with DNA via electrostatic, hydrophobic and π–π interaction. ► The stronger interaction between DNA and [Cn-4-Cnim]Br2 with longer tails demonstrates the important contribution of the hydrophobic interaction.

The interactions between surfactants and polymers are widely investigated due to favorable changes on properties in their mixtures. Silicone surfactants and pluronic copolymers, both having low toxicity, are used in the detergent, cosmetics, medical, and pharmaceutical fields. Their mixture may gain better performance in their further applications. Therefore, we investigated the interaction between an ethoxy-modified trisiloxane (a silicone surfactant named Ag-64) and a block polyether F127 in this paper. From aggregation behavior of Ag-64 and F127, the formation mechanism and conformation of the aggregates were proposed based on experiments and dissipative particle dynamics (DPD) simulation. The surface activity and aggregation behavior of Ag-64 are affected by F127 in aqueous solutions. As the amounts of added Ag-64 increase, two types of aggregates (Ag-64/F127 aggregate with F127 as skeleton and the “pearl- necklace” aggregate in which Ag-64 micelles are strung along F127 chain) form successively. At higher polymer concentration, F127 twists together to form a coil/cluster aggregate with Ag-64. The results of DPD simulation approve that two main factors, the hydrophobic association and twist of F127 coil, contribute to the formation of different aggregates of Ag-64 and F127.

The surface properties of gelatin solutions without and with ionic liquid-type imidazolium gemini surfactants have been investigated via surface shear and dilational rheology as well as surface tension measurements. Both the surface shear and dilational rheological properties show that the strength of gelatin film is enhanced in the presence of 0.005 mmol L−1[C12-4-C12im]Br2, and the storage modulus is larger than loss modulus for gelatin/[C12-4-C12im]Br2, indicating that gelatin/[C12-4-C12im]Br2 is an elastic film. With increasing the concentration of imidazolium gemini surfactant, the dilational modulus increases firstly and then passes through a maximum value, due to the electrostatic and hydrophobic interactions between surfactant molecules and gelatin chains. Although the surface tension of gelatin/surfactant mixed solution is identical to that of the pure surfactant solution at high surfactant concentration, the dilational modulus suggests that the surfactant molecules are unable to fully replace gelatin molecules from the air/water surface. The structure of the gemini surfactant has great effect on the surface viscoelastic modulus of gelatin, it is found that the gelatin film in the presence of imidazolium gemini surfactant with longer hydrophobic chain or longer spacer reveals the larger strength.

The phase behavior of a kind of star-like block polyether in aqueous solution is studied by MesoDyn simulation method in the absence and presence of shear. With the polyether concentration increasing, different mesoscale structures are found in the absence and presence of shear. (1) In the absence of shear, there are four different structures formed with the increasing polyether concentration. The first is micellar phase, including sphere-like micelle and wormlike micelle, the second is bicontinuous phase, the third is lamellar phase, and the fourth is reversed micellar phase, including reversed worm-like micelle and reversed hexagonal micelle. (2) In the presence of shear, there are three morphologies formed in all studied concentrations; they are hexagonal phase, lamellar phase and reverse hexagonal phase, which align in the flow direction. The detailed structures and forming mechanisms of different aggregates are given by analyzing simulation results.

The aggregation behaviors of sodium deoxycholate (NaDC) at the air/water surface were investigated via surface tension and oscillating bubble measurements in the absence and presence of three alkaline amino acids, namely, l-Lysine (l-Lys), l-Arginine (l-Arg), and l-Histidine (l-His). The results of surface tension measurements show that NaDC has a lower ability to reduce the surface tension of water, because NaDC molecules orient at the surface in an oblique direction and tend to aggregate together, which is approved by molecular dynamics (MD) simulation. l-Lys is the most efficient of the three amino acids in reducing the critical aggregation concentration (cac) of NaDC in aqueous solution. The influence of amino acids on the dilational rheological properties of NaDC was studied using the drop shape analysis method in the frequency range from 0.02 to 0.5 Hz. The results reveal that the absolute modulus passes through a maximum value with increasing NaDC concentration. The addition of amino acids increases the absolute modulus of NaDC, and the maximum value is observed at much lower concentration. From the perspective of structures of amino acids, the performance of l-Arg is similar to that of l-His, and both of them bring out a smaller effect on the absolute modulus than that of l-Lys. From the above results, it may be presumed that electrostatic and hydrophobic effects are important impetus during the interaction between amino acids and NaDC at the air/water surface. Hydrogen bonding is so ubiquitous in the system that the difference of hydrogen bonding between NaDC and amino acid is ignored.

The aggregation behaviors of branched block polyether Tetronic 1107 (T1107) at an air/liquid surface was investigated in mixed solvents consisting of water and one of the following polar cosolvents: ethanol, n-propanol, ethylene glycol (EG), or glycerol (GLY). Surface tension measurements provide information about the effects of cosolvents on the critical micellization concentration (cmc), the standard Gibbs energy (ΔG°mic), the maximum surface excess concentration (Γmax), the minimum area per polyether molecule at the air/liquid surface (Amin), and the standard free energy of adsorption (ΔG°ads). The addition of ethanol and n-propanol to water disfavors the micellization and progressively increases the cmc of T1107, whereas the cmc decreases with the addition of EG and GLY. The values of ΔG°mic of T1107 are all negative in mixed solvents, and their absolute values become smaller as the ethanol or n-propanol content increases but become larger as the EG or GLY content increases. The cosolvents have a significant effect on the surface adsorption and cmc, and the order is as follows: n-propanol–water > ethanol–water > water > EG–water > GLY–water. The octanol/water partition coefficient (log P) of the cosolvent is used to correlate the effects, and it could capture the effect of cosolvents on the cmc qualitatively. The surface dilational rheological properties of T1107 in water and water–alcohol mixtures were also studied by surface dilational viscoelasticity and surface tension relaxation measurements. The dilational elasticity decreases monotonously in the presence of ethanol or n-propanol. With the increasing concentration of EG and GLY, the dilational elasticity of T1107 passes through a maximum that coincides with the change in Γmax.

The properties of adsorbed monolayers of three hydrocarbon surfactants with the same hydrophobic tail, sodium dodecyl sulfate (SDS), dodecyltrimethylammonium bromide (DTAB) and octaethylene glycol dodecyl ether (C12E8) at the air/water surface in the absence and presence of a dimethylsiloxane ethoxylate-propoxylate (DSEP) were studied via molecular dynamics simulations to compare the effect of the headgroups on the aggregation behaviors of surfactant mixtures. The structures and dynamical properties of the monolayers were greatly affected after adding DSEP. In the presence of DSEP, SDS monolayer was better ordered and more compact, whereas C12E8 monolayer was relatively disordered. Some DTAB molecules immerged into water, and the others adsorbed at the surface were in less compact but well-ordered arrangement. The reason for the appearance of different types of monolayers was also discussed, with the goal of providing a theoretical approach for their further applications.

The block polyethers with different structure and composition were synthesized by anionic polymerization and used to disperse single-walled carbon nanotubes (SWNTs). The block polyethers with the structure of branch or benzene ring had better dispersion ability than the commercial Pluronic block polyethers (L64 and F127). In order to compare the parameters, dispersion limit and efficiency of polyethers for SWNTs were defined. UV–vis–near infrared absorbance spectra showed that eight-branch polyether AE82 had much larger dispersion limit and efficiency than five-branch AE52. BPE containing benzene rings in the molecule had a slightly lower dispersion limit but larger dispersion efficiency than AE82. The defect density of SWNTs dispersed in polyether aqueous solutions was investigated by Raman spectroscopy. The polyethers AE83 and BEP with the structure of poly(ethylene oxide)–poly(propylene oxide) dispersed less defective SWNTs than AE82 and BPE, indicating that the variation of polyether structure and composition could influence the defect density of SWNTs besides dispersion limit and efficiency.

Calcium carbonate (CaCO3) was crystallized in the presence of O-carboxymethylchitosan (CMCS) by a vapor diffusion method. The CaCO3 particles were characterized by scanning electron microscopy (SEM), the energy dispersion spectroscopies (EDS), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetry analysis (TGA) and N2 adsorption–desorption methods. By varying the concentrations of CMCS, Ca2+ and Mg2+ ions, and temperature, the CaCO3 nanocrystals with different morphologies were produced. Based on the analysis of CaCO3 particles obtained under different conditions, the mechanism of the CaCO3 crystallization in the presence of CMCS was proposed.Typical SEM images of the CaCO3 particles precipitated in CMCS solutions. The insert is the image of CaCO3 particles after being calcined at 673 K for 12 h.

The ability of a mixture of an ethoxy-modified trisiloxane (a silicone surfactant, named Ag-64) and a block copolymer F127 to disperse carbon nanotubes (CNTs) was investigated by experimental investigation and molecular dynamics simulation. Dispersions with large amounts of individual CNTs were obtained. The quantity of dispersed CNTs was obviously larger than each quantity of the dispersions with individual surfactants at the same concentration, even exceeded the sum of them. The mechanism of dispersing CNTs was also discussed. It can be inferred that Ag-64 and few F127 could wrap onto the surface of CNTs to dispart clusters to individuals, and the other F127 interact with adsorbed Ag-64 and F127 to generate stronger steric stabilization. Thus, a synergistic effect on dispersing CNTs by the mixture of Ag-64 and F127 was observed.

The comparison of aggregation behaviors between the branched block polyether T1107 (polyether A) and linear polyether (EO)60(PO)40(EO)60 (polyether B) in aqueous solution are investigated by the MesoDyn simulation. Polyether A forms micelles at lower concentration and has a smaller aggregation number than B. Both the polyethers show the time-dependent micellar growth behaviors. The spherical micelles appear and then change to rod-like micelles with time evolution in the 10 vol% solution of polyether A. The micellar cluster appears and changes to pseudo-spherical micelles with time evolution in the 20 vol% solution of polyether A. However, the spherical micelles appear and change to micellar cluster with time evolution in the 20 vol% polyether B solution. The shear can induce the micellar transition of both block polyethers. When the shear rate is 1 × 105 s−1, the shear can induce the sphere-to-rod transition of both polyethers at the concentration of 10 and 20 vol%. When the shear rate is lower than 1 × 105 s−1, the huge micelles and micellar clusters can be formed in the 10 and 20 vol% polyether A systems under the shear, while the huge micelles are formed and then disaggregated with the time evolution in the 20 vol% polyether B system.

Molecular dynamics simulations have been performed to investigate the effect of inorganic salts on the structural and dynamic properties of alkyl benzene sulfonate monolayer formed at the air/water interface. The alkyl benzene sulfonates are two surfactant isomers in the family of sodium hexadecane benzene sulfonates defined by 1C16 and 5C16, indicating a benzene sulfonate group attached to the first and fifth carbon atom in hexadecane backbone. It has been observed that both benzene ring groups and headgroups (−SO3−) are hydrated due to their polar nature. Water molecules can form stable hydrogen bonds with headgroups of surfactants, and the counterions (Na+, Mg2+, or Ca2+) are distributed close to the air/water interface. The stronger electrostatic repulsion drives the 1C16 monolayer arranged in disorder in comparison with 5C16, and the presence of inorganic salts may screen electrostatic repulsions between headgroups and decrease the thickness of the interfacial water layer, which follows the series Ca2+ > Mg2+ > Na+. The order of inorganic salt tolerance of two surfactants is 5C16 > 1C16. The counterions may penetrate into the hydration shell of the surfactant headgroups and restrict the mobility of the water molecules situated in this area.

The surface property of an amphiphilic cyclodextrin 2-O-(hydroxypropyl-N,N-dimethyl-N-dodecylammonio)-β-cyclodextrin (HPDMA-C12-CD) was investigated using oscillating bubble rheometer and electrical conductivity method at different temperatures. The surface tension and dilational viscoelasticity of HPDMA-C12-CD were provided. The results showed that HPDMA-C12-CD could adsorb on the air–water interface, which decreased the surface tension of water efficiently. Critical micelle concentration (cmc) can be clearly defined from the surface tension isotherm. pC20 and πcmc were derived from the surface tension isotherms as well. The thermodynamic parameters (ΔG   0m  , ΔH   0m  , −TΔS   0m) derived from electrical conductivity indicated that the micellization of HPDMA-C12-CD was entropy-driven at lower temperature, while it was enthalpy-driven at higher temperature. The dilational modulus appeared a maximum value while the phase angle appeared two maxima as a function of HPDMA-C12-CD concentration.

The location of the aromatic molecule, benzyl alcohol, in two structurally similar surfactants, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and sodium bis(2-ethylhexyl) phosphate (NaDEHP), in the absence and presence of water-soluble polymer, poly(vinylpyrrolidone) (PVP) is investigated by NMR. According to the variation of the chemical shift of respective protons of AOT and NaDEHP molecules in the presence of probe molecules, it is interesting to find that most of the benzyl alcohol molecules are located around the surface of AOT micelles, while they mainly incorporate in the hydrophobic chain or close to the core of NaDEHP micelles. All the proton chemical shifts of the two studied surfactants moved to higher fields with the increasing benzyl alcohol concentration. The chemical shifts of different protons for the studied surfactant–PVP system with the increasing content of benzyl alcohol are also investigated. In the AOT–PVP system it is found that PVP is wrapped on the surface of AOT micelles due to the weak electrostatic interaction between PVP and AOT molecules, which makes the benzyl alcohol molecules enriched around the surface of the micelles. However, for the NaDEHP-PVP system, the results indicate that PVP has no distinct effect on the location of probe molecules, that is, most of the benzyl alcohol molecules solubilized close to the core of the NaDEHP micelles or in the hydrophobic chain of NaDEHP molecules in the presence of PVP. This is in agreement with our previous results from the surface tension and dynamic light scattering measurements. This study provides important insight into the probe molecules location in the double-chain surfactant micelles in the presence of water-soluble polymer and will be helpful for the application of amphiphile self-assembly in drug delivery.

A complex system that consists of cetyltrimethylammonium bromide (CTAB), Triton X-100 (TX-100), and hydrolyzed polyacrylamide (HPAM), differing from the old-time conceptions of the displacement system, has been studied. It is indicated that the complex system is capable of satisfying requirements of high viscosity and low interfacial tension under conditions of higher temperature and mineralized water. The dynamic interfacial tension of the complex system depends upon multifarious factors, such as the ratio of TX-100/CTAB, concentrations of HPAM and surfactants, temperature, and the mineralized degree, etc. Especially, it is interesting that the dynamic interfacial tension of the complex system cannot reach an ultralow value (<1 × 10−2 mN·m−1) when one component is lacking among the HPAM/TX-100/CTAB complex system. From the results of the adsorption on quartz sands and on the core flooding tests, it can be concluded that the HPAM/TX-100/CTAB complex system is suitable for use as a displacement system in an oil field after polymer flooding.

The block polyethers with various branch structure, such as TEPA[(PO)36(EO)100]7, TEPA[(PO)36(EO)100(PO)36]7, and TEPA[(PO)36(EO)100(PO)56]7 were synthesized. Moreover, the aggregation behavior was investigated via the measurements of equilibrium surface tension, dynamic surface tension, and surface dilational viscoelasticity, in order to probe the effect of the block structure on the property of the branched block polyethers. The surface tension results show that the efficiency and effectiveness of the block polyethers to lower surface tension increase with the increase of the PO group numbers. The maximum surface excess concentration (Γmax) values and the minimum occupied area per molecule at the air/water interface (Amin) values of the branched block polyethers obtained from Gibbs adsorption equations increase and decrease with the increases of the PO group numbers, respectively. The dynamic parameters n and t∗ representing the diffusion speed of the polyether molecules from bulky solution to the subsurface and from the subsurface to the air/water surface are obtained according to the equation proposed by Rosen. The results show that the n values firstly increase and then decrease and t∗ values decrease with the increase of the polyether concentrations. The results of surface dilational viscoelasticity show that the dilational modulus of TEPA[(PO)36(EO)100(PO)56]7 is the largest among the three block copolymers at the low concentration (<1 mg L−1) but that of TEPA[(PO)36(EO)100]7 is the largest at the high concentration (>1 mg L−1).

The aggregation of ionic liquid-type imidazolium gemini surfactant [C12-4-C12im]Br2 on silicon wafer, which is compared with its monomer [C12mim]Br, have been studied. AFM morphology images and contact angle measurements suggest that the aggregations of [C12-4-C12im]Br2 and [C12mim]Br on silicon wafer follow different mechanisms. Below the critical surface aggregation concentrations (CSAC), both surfactant molecules are adsorbed with their hydrophobic tails facing the air. But above the CSAC, [C12-4-C12im]Br2 molecules finally form a bilayer structure with hydrophilic head groups facing the air, whereas [C12mim]Br molecules form a multilayer structure, and with increasing its concentration, the layer numbers increase with the hydrophobic chains and hydrophilic head groups facing the air by turns. Besides, the watery wettability of [C12-4-C12im]Br2-treated silica surface is lower than that of [C12mim]Br at the concentration of 5.0 cmc, and the infrared spectroscopy suggests that the poorer watery wettability of [C12-4-C12im]Br2 may be relative to the less-ordered packing of methylene chains inside the aggregate. These different aggregation behaviors for the two surfactants ascribe to the different molecular structures and electrostatic interactions. This work would have certain theoretical guidance meaning on the modification of solid surface.

The interaction between bovine serum albumin (BSA) with N, N′-bis(dimethylalkyl) ethylammonium dibromide (C12C2Cm, m = 8, 12) was investigated by spectral methods. It can be seen that C12C2C8 and C12C2C12 mainly interact with tryptophan residues of BSA from synchronous fluorescence spectra. Fluorescence, far-UV, and near-UV circular dichrosim spectra of BSA are changed by addition of dissymmetric and symmetric gemini surfactant. For surfactant solution, the polarity of the microenvironment surrounding pyrene is lower while the fluorescence lifetime of it is longer and the microviscosity is higher in the presence of BSA than those in the absence of BSA. But compared with C12C2C12, C12C2C8 has lower binding ability with BSA due to the shorter hydrophobic tail and lower symmetry.

The aggregation behavior and thermodynamic properties of micellization for the ionic liquid-type gemini imidazolium surfactants with different spacer length ([C12–s–C12im]Br2, s = 2, 4, 6) have been investigated by means of surface tension, electrical conductivity, dynamic light scattering and fluorescence measurements. The values of cmc, γcmc, Γmax, Amin, πcmc, pc20 and cmc/pc20 suggest that the shorter the spacer, the higher the surface activity of [C12–s–C12im]Br2 is. The cmc and γcmc values are decreased significantly in the presence of sodium halides, and the values decrease in the order NaCl < NaBr < NaI. The thermodynamic parameters of micellization (\(\Delta G_{\text{m}}^0 \), \(\Delta H_{\text{m}}^0 \), \(\Delta S_{\text{m}}^0 \)) indicate that the micellization of [C12–2–C12im]Br2 and [C12–4–C12im]Br2 is entropy-driven, whereas aggregation of [C12–6–C12im]Br2 is enthalpy-driven at lower temperature but entropy-driven at higher temperature. Finally, the fluorescence measurements show that the micropolarity of micelles increases but the aggregation numbers decrease with increasing the spacer length of [C12–s–C12im]Br2.

Surface tension and dilational viscoelasticity of water in the presence of surfactants Tyloxapol and Triton X-100 with cetyl trimethylammonium Bromide (CTAB) at 25 °C are investigated. The results show that there is synergistic behavior in both the mixtures at higher mole fraction of nonionic surfactant. According to the Rubingh and Rosen theory, the results predict nonideal mixing and attractive interaction between the constituent surfactants in the mixed micelle and layer. By using the Maeda theory, the results suggest the chain−chain interaction among surfactants does not seem to be high. The surface dilational viscoelasticity results show that the Tyloxapol adsorption layer has the highest dilational modulus |ε| value among three single surfactants. Also, it indicates the |ε| maximum values of surfactant mixtures are usually between that of the single surfactant. Moreover, it is worth noting that the |ε| maximum values of Tyloxapol/CTAB mixtures are always higher than those of TX-100/CTAB ones.

The mesoscopic dynamic (MesoDyn) simulation method was used to simulate the aggregation behavior of Pluronic copolymer EO13PO30EO13 (L64) and EO26PO40EO26 (P85) solutions in the presence of SDS. With a simple copolymer model, the morphology and kinetic formation process of copolymer aggregate were obtained. Some factors influencing the aggregation behavior of the copolymer were discussed, such as concentration, temperature and EO/PO ratio. Simulation results show that the presence of SDS induces the L64 spherical micelles formed at much lower L64 concentration comparing with the system without SDS. At the same L64 concentration, an increase in SDS concentration results in an increase in the size of L64 micelles and decrease in the number of micelles. The morphology of L64 aggregates undergoes transitions from spherical micelles → rod-like micelles → bicontinuous phases with L64 concentration increasing. The kinetic process of micelles formation can be divided into three stages and the first diffusion stage will disappear when L64 concentration is above 30%. Temperature investigation indicates that the formation of aggregates is an exothermic process, and it becomes more difficult and the formation rate decreases with temperature increasing. The size of micelles formed by P85 with higher EO/PO ratio value is larger than that formed by L64 micelles. Further more, P85 is more difficult to form micelles comparing with L64. This is caused by the more hydrophilic EO groups in P85, leading to the fact that there are more water molecules amongst P85 micelles.

Aggregation behavior of mixture of polyoxyethylene tert-octylphenyl ether (TX-100) and its oligomer Tyloxapol with cetyltrimethylammonium bromide (CTAB) at the crude oil/water interface in the presence of hydrolyzed polyacrylamide (HPAM) was investigated via the interfacial tension (IFT) measurement by spinning drop technology at 70.0 °C in 10,000 mg L−1 brine solution. Effects of HPAM concentration and mass ratios of nonionic surfactant/CTAB on the dynamic IFT between crude oil and aqueous solution were studied in detail. For single surfactant systems, it was found that the ability of lowering IFT for CTAB was better than that for nonionic surfactant, while the IFTs yielded by system with Tyloxapol were higher than that yielded by the system with TX-100; and the IFTs obtained by mixed surfactants systems were always higher than that obtained by CTAB. Interestingly, the ultra-low IFT was obtained for all surfactant mixtures in the presence of HPAM, i.e., HPAM was as an inducer to produce the ultra-low IFT between crude oil and mixed brine solution of TX-100 and its oligomer Tyloxapol with CTAB. However, there existed both synergism and antagonism between HPAM and mixed surfactants on crude oil/water IFT reduction. Only when mass ratios of nonionic surfactant/CTAB and the amount of HPAM were appropriate could the ultra-low IFTs be obtained. And the difference between HPAM/TX-100/CTAB and HPAM/Tyloxapol/CTAB mixed systems in reducing IFT was that the time to reach ultra-low IFT was longer for the latter system. The result might be of real significance in the enhanced oil recovery (EOR).

CdS–Silica core–shell (assigned as CdS@SiO2) nanoparticles have been synthesized by directly covering silica on the CdS nanocrystalline surface in the same reverse microemulsion composed of polyoxyethylene (10) tertoctylphenyl ether (Triton X-100)/1-hexanol/cyclohexane/H2O. The influencing factors, such as the volume ratio of CdCl2 aqueous solution, ethanol solution containing thioacetamide (TAA), ammonia and tetraethyl orthosilicate (TEOS) were investigated in detail. The transmission electron microscopy (TEM) images showed CdS nanocrystalline aggregated in the silica interior, and the spherical uniformity and regularity of CdS@SiO2 nanoparticles varied along with the variation of reactants. The X-ray powder diffraction (XRD) and selected area electron diffraction (SAED) proved both uncovered CdS nanocrystallines and CdS@SiO2 nanoparticles have zinc blend structures. The UV–vis absorption and photoluminescence (PL) spectra demonstrated the quantum confinement effect and the spectral change of the CdS nanocrystalline after covered by silica. A mechanism of the formation of CdS@SiO2 nanoparticle was proposed based on the analysis of low- and high-resolution electron microscopy (HR-TEM) results.

A series of ionic liquid-type Gemini imidazolium surfactants with four-methylene spacer groups were synthesized ([Cn-4-Cnim]Br2, n=10n=10, 12, 14). The surface activity and thermodynamic properties of micellization between the Gemini imidazolium surfactants and their corresponding monomers ([Cnmim]Br, n=10n=10, 12, 14) were compared by means of surface tension and electrical conductivity measurements. The values of cmc, γcmcγcmc, pc20pc20, ΓmaxΓmax, and AminAmin derived from surface tension measurement at 25 °C suggest that the surface activity of [Cn-4-Cnim]Br2 is higher than that of [Cnmim]Br. While the thermodynamic parameters of micellization (ΔGm○, ΔHm○, ΔSm○) derived from electrical conductivity indicate that the micellization of [Cn-4-Cnim]Br2 is entropy-driven, aggregation of [Cnmim]Br is entropy-driven at low temperature but enthalpy-driven at high temperature. Finally, the activation energy of conductance (EaEa) that is associated with the effective charge is also obtained for [Cn-4-Cnim]Br2 and it is constant below the cmc, but it increases above the cmc.The thermodynamic parameters of micellization obtained from conductivity measurements indicate that negative values of ΔGm○ arise due to large positive ΔSm○ values, and so the micellization process is entropy-driven.

The ability of dispersing carbon nanotubes (CNTs) in aqueous solutions by a starlike amphiphilic block copolymer with PPO−PEO segments (AP432) was investigated in detail. For comparison, two commercially available linear amphiphilic block copolymers, Pluronics L64 and F127, were also selected. It was found that AP432 and F127 can get good CNT dispersions, while L64 was proved to be unable to disperse CNTs. AP432 with five branches could disperse CNTs efficiently at much lower concentrations compared with the linear F127, although it has a smaller molecular weight and shorter terminal EO groups. This indicated clearly that, once branched, copolymers would get a much better ability to disperse CNTs. Increasing concentration of AP432 or F127 would disperse more CNTs, but at high copolymer concentrations the aggregation of dispersed CNTs was observed, which may be related to the free micelles formed by AP432 or F127 around CNTs. Other influencing factors such as the mass ratio of CNTs to copolymers and sonication time and strength were also discussed. From the molecular dynamics simulation results, it can be found that copolymers with five branches can gain better steric repulsions between adjacent CNTs, which is consistent with the experimental results.

The aggregation behavior and the interaction of four mixed systems for a cationic fluorocarbon surfactant, diethanolheptadecafluoro-2-undecanolmethylammonium chloride (DEFUMACl), mixing with cationic hydrocarbon surfactants, alkyltrimethylammonium chloride, CnTACl (n = 12, 14, 16, and 18; where n = 12 is DTACl, n = 14 is TTACl, n = 16 is CTACl, and n = 18 is OTACl), were studied by 1H and 19F NMR in more detail. The results of 19F NMR measurements strongly indicate that in the three mixed systems of DEFUMACl/DTACl, DEFUMACl/TTACl, and DEFUMACl/CTACl at different molar fractions of fluorocarbon surfactant (αF = (cDEFUMACl/cDEFUMACl + cCnTACl)), with an increase of the total concentration of fluorocarbon and hydrocarbon surfactants (cT = cF + cH), the mixed micelles at the first break point and the individual DEFUMACl micelles at the second break point form. However, three different types of micelles were determined in DEFUMACl/OTACl mixtures by 19F NMR measurements, OTACl-rich and DEFUMACl-rich mixed micelles and individual DEFUMACl micelles, respectively. The chemical shifts of proton Δδ (1H) for −CH3 in the mixed systems of DEFUMACl/CnTACl (n = 12, 14, 16, and 18) have different variation trends from the 19F NMR measurements. For the two systems of DEFUACl/DTACl and DEFUMACl/TTACl, the mixed micelles form at the first break point. At the second break point, for lower αF values the DTACl-rich and TTACl-rich mixed micelles form with a strong downfield shift and for higher αF values DEFUMACl-rich mixed micelles form with a strong upfield. For the other two systems of DEFUMACl/CTACl and DEFUMAC/OTACl, the chemical shifts of proton Δδ (1H) of −CH3 increase with an increase of the total concentration of DEFUMACl/CTACl or OTACl, and mixed CH- and CF-surfactant micelles form. At higher total concentration, the greater effect of fluorinated chains of DEFUMACl on CH-chains was obvious, resulting in the strong upfield chemical shifts. In cationic fluorocarbon and hydrocarbon surfactant mixtures, the different kinds of micelles observed by 19F and 1H NMR measurements could be caused by the increase in alkyl chain length of hydrocarbon surfactants with different critical micelle concentrations. Combining two theoretical models for mixing, for the four different chain-length hydrocarbon surfactants studied, one can conclude that the two components of mixtures interact with each other and form mixed micelles in two completely different ways according to their molecular properties and cmc values in a certain range of total concentrations. One is close to an ideal mixing case with the formation of one type of mixed micelles, such as the DEFUMACl/DTACl and DEFUMACl/TTACl systems. The other is a demixing case with the formation of two types of micelles, i.e., fluorocarbon-rich and hydrocarbon-rich mixed micelles, such as DEFUMACl/CTACl and DEFUMACl/OTACl systems. However, as the total concentrations of the mixed systems are high enough, the four systems tend to demix and to form individual micelles of corresponding components due to the initial respective interaction between fluorocarbon and hydrocarbon chains. That is to say, at high total concentration, the individual DEFUMACl micelles in all four systems could form. These results may be primarily directed toward acquiring an understanding of the mechanism of CF−CH mixtures in aqueous solution and secondarily directed toward providing more detailed information on nonideal mixing.

The interaction between sodium oleate (C17H33COONa) and partially hydrolyzed polyacrylamide (HPAM) was investigated by rheological measurements. Mainly four series with concentration of HPAM to be 0.1 wt%, 0.2 wt%, 0.4 wt% and 0.6 wt%, respectively, were studied. At low concentrations of C17H33COONa (cC17H33COONa<0.01 wt%)(cC17H33COONa<0.01 wt%), an increase in viscosity is observed due to interpolymer cross-linking through hydrogen bonding between C17H33COONa and HPAM. With increasing concentration of C17H33COONa, the repulsion between C17H33COONa micellar aggregates attached to the HPAM chains increases and the coil of HPAM shrinks. As a result, the network between C17H33COONa and HPAM collapses and the viscosity of the system decreases. Correspondingly, the critical angular frequency ω* obtained from oscillation measurements shows a decrease at low concentrations of C17H33COONa, passes through a minimum and then increases continuously at higher C17H33COONa concentrations. Polarized microscopic observations reveal a possible transition from three dimensional network structures to lamellar structures induced by C17H33COONa addition.

The interaction between cetyltrimethylammonium bromide (CTAB) and β-cyclodextrin (β-CD) was studied via surface tension and dilational viscoelasticity methods. The effect of sodium bromide and sodium chloride on the interaction between CTAB and β-CD were studied as well. The surface tension isotherms provided a series of parameters, including apparent critical micelle concentration (cmc*), surface tension at the cmc* (γcmc), stoichiometry of the complex (R), and the efficiency of adsorption (pC20). The addition of NaBr and NaCl decreases the cmc* of CTAB/β-CD solution. CTAB molecules enter the cavities of β-CD molecules thus formed both 1:1 and 1:2 inclusion complexes. From the change of γcmc, it can be seen that the CTAB/β-CD complexes (1:1) act as short-chain alcohol, which decrease γcmc, but the depression of cmc* is too small to be detected. R first decreases then increases as a function of NaBr and NaCl. Compared to NaCl, NaBr increases R more efficiently. The presence of NaBr and NaCl increases pC20 of CTAB/β-CD solution. The results obtained from the dilational viscoelasticity measurements at low dilational frequencies (0.005–0.1 Hz) reveal that the dilational modulus passes through a maxium value with increasing concentration of β-CD at a given concentration of CTAB. The addition of both NaBr and NaCl decreases the dilational modulus of a given concentration CTAB/β-CD solution.

The dilational rheological properties of 1,2-ethane bis(dimethyl dodecyl ammonium bromide) (C12C2C12·2Br) at air/water interface were investigated using oscillating barriers method at low frequency (0.005–0.1 Hz). The dilational modulus of C12C2C12·2Br is higher than that of dodecyltrimethyl ammonium bromide (DTAB), indicating the strength against perturbation of interfacial layer of the former is greater. This phenomenon is explained by molecular dynamics simulation. Many factors have great effect on the dilational rheology such as bulk concentration, temperature and NaBr. The results reveal that the dilational modulus passes through a maximum value with C12C2C12·2Br concentration increasing. It is also found that the maximum value of the dilational viscous component appears at different concentration with the dilational frequency increasing. And the higher the dilational frequency is, the higher the concentration corresponding to the maximum value of the dilational viscous component is. When temperature rises, the dilational modulus decreases gradually. Moreover, the addition of NaBr can increase the dilational modulus of C12C2C12·2Br.

MesoDyn density functional simulation method is used to study the interactions between dodecyl oxypropyl β-hydroxyltrimethylammonium bromide (C12NBr) and Xanthan (XC). The micro dynamic process of aggregate formation and the aggregate morphology are reported. Interaction between XC and nonyphenyloxypropyl β-hydroxyltrimethylammonium bromide (C9phNBr) is compared with that between XC and C12NBr. Simulation results show that the aggregate morphology of XC/C12NBr and XC/C9phNBr is of rod-like shape with helix characteristic. The binding of C9phNBr to XC is more difficult than that of C12NBr to XC. In addition, three stages for the dynamic evolution of surfactant binding to XC are observed. The simulation results agree with binding isotherms of C9phNBr (C12NBr) to XC obtained via the potentiometric titration method, which shows a typical cooperative binding between C9phNBr (C12NBr) and XC.

The aggregation behavior of fluorinated surfactant in aqueous solution was investigated using dissipative particle dynamics (DPD) simulation method. Simulation results show that fluorinated surfactants behave mainly as their hydrocarbon analogues, having similar sequences of phases and aggregate structures, which are capable of building micelle, hexagonal phase and lamellar phase. But fluorinated surfactants also show interesting differences from hydrocarbon analogues, which can easily form hexagonal and lamellar structures with comparative little curvature. They can also form ellipsoid or rod-like micelles even in very low concentrations instead of spheroid ones. The dynamic aggregation behavior of fluorinated surfactants, as well as the comparison with hydrogenated ones, was also investigated.Computer simulation demonstrates that the fluorinated and hydrogenated surfactants both can build lamellar phase at high concentrations. The density values in the core regions indicate that fluorinated surfactants form loosely packed aggregate structure. Therefore, fluorinated surfactants have a tendency to form less curvature aggregate.

The all atom molecular dynamics method was used in the investigation of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) at isooctane/water interface in order to get dynamic properties in detail. We used a simulation box enclosing 20 surfactant molecules, which the surfactant number was kept constant during the simulation. After reaching the thermodynamic equilibrium, it turned out that the alkyl chains of AOT molecules were dissolved well in the isooctane phase and the isooctane/water interface disappeared. We also carried out investigations of the effects of some additives (NaCl, CaCl2 and Na2SO4) on the dynamic properties for the system. Furthermore, the radial distribution function, mean squared displacement and concentration profiles of these systems were calculated.

The interaction of polyvinylpyrrolidone (PVP) with sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and sodium bis(2-ethylhexyl) phosphate (NaDEHP) in the solution was investigated by dissipative particle dynamics (DPD) simulation. The calculated interaction parameters between PVP and AOT or NaDEHP showed that AOT is in favor to form polymer–surfactant complex with PVP in contrast to NaDEHP. The experiment of surface tension measurement proved the computational results. In DPD simulation, the mean square end-to-end distance 〈r2〉 of polymer chain firstly increases in size, then reduces and increases again. And some polymer–surfactant complexes were also shown. One conclusion is that mesoscopic simulation can be considered as an adjunct to experiment and provide other valuable information for the experiment.

Poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) ((EO)20–(PO)72–(EO)20) and O-(hydroxy isopropyl) chitosan (HPCHS) were employed as control agents of calcium carbonate crystal growth. The effect of the concentrations of polymers, [Ca2+] and [CO32−], the ratios of [Ca2+]–[CO32−] and the initial pH of the solutions were investigated. The obtained CaCO3 particles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The particles are mainly calcite with various morphologies; their size and morphologies are influenced by the polymer content. For (EO)20–(PO)72–(EO)20 systems, the initial pH has a notable influence; but in the HPCHS solution pH shows little influence. The ratio of [Ca2+]–[CO32−] clearly affects the CaCO3 particle size and aggregation degree. HPCHS showed more significant influence on CaCO3 crystallization than (EO)20–(PO)72–(EO)20. The mechanisms of the CaCO3 crystallization as controlled by (EO)20–(PO)72–(EO)20 and HPCHS are proposed and demonstrated by the molecular dynamics simulations.

Calcium carbonate (CaCO3) was crystallized in xanthan (XC) aqueous solutions. The CaCO3 particles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermogravimetry analysis (TGA) methods. The concentrations of XC, Ca2+ and CO32− ions and the ratios [Ca2+]/[CO32−] and [Mg2+]/[Ca2+] show evident influence on the aggregation and growth of CaCO3 particles. The presence of Mg2+ ions influences not only the morphology, but also the polymorph of CaCO3.

Polyvinyl alcohol (PVA) hydrogels have been proposed for use as promising biomaterials in biomedical and tissue engineering, and graphene oxide (GO) has been recognized as a unique two-dimensional building block for various graphene-based supramolecular architectures. In this article, we systematically studied the influence of three kinds of PVA with different molecular weights on the interaction between PVA and GO. Moreover, the effects of PVA on the gelation of GO were also investigated. The native PVA hydrogel, as well as PVA–GO hybrid hydrogels, have been thoroughly characterized by the phase behavior study and various techniques including field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and rheological measurements. It can be seen that with the increase of the molecular weight of PVA, the addition of GO can effectively promote the gelation of PVA which can be reflected by a decrease of the critical gel concentration (CGC) for PVA–GO hydrogels. Dye adsorption experiments indicate that the toxic dye, i.e., methylene blue (MB), was efficiently entrapped in the PVA–GO xerogels. It is also demonstrated that the gelation of PVA and GO composites can be promoted by different supramolecular interactions, including hydrogen bonding and electrostatic interaction. This work indicates that the PVA–GO composite is a good candidate for preparing “super” and “smart” hydrogels and will enable further studies on the supramolecular chemistry of PVA, graphene and its derivatives.