Biphenyl-contained monomer of 1,4-bis[2-(3,4-epoxy cyclohexyl ethyl) dimethylsilyl] biphenyl (BP-SiH-EP) was prepared via hydrosilylation reaction of 1,4-bis(dimethylsilyl) biphenyl (BP-SiH) and 1,2-epoxy-4-vinylcyclohexane in the presence of Karstedt’s catalyst. 1H-NMR, 13C-NMR and FTIR were used to characterize the structure of the obtained monomer. BP-SiH-EP was then cured by methyl hexahydrophthalic anhydride (MeHHPA) with 1-cyanoethyl-2-ethyl-4-methylimidazole as an accelerator. The polymerization behavior was studied by DSC. The results of DMA measurement demonstrate that the cured BP-SiH-EP/MeHHPA can maintain high storage modulus (> 1 GPa) in a wide range of temperature up to 176 °C. According to the damping factor curve of DMA, cured BP-SiH-EP/MeHHPA exhibits a high glass transition temperature (Tg) of 192 °C, which is 20 °C higher than that of cured 1,4-bis[2-(3,4-epoxy cyclohexyl ethyl) dimethylsilyl] benzene (DEDSB)/MeHHPA. TGA results show that cured BP-SiH-EP/MeHHPA has good thermal stability (T5% = 339 °C) due to the high heat-resistance of rigid biphenyl group. Moreover, the crosslinking density of cured BP-SiH-EP/MeHHPA should be lower than that of cured DEDSB/MeHHPA estimated from their chemical structures, which conflicts with the calculated results based on the rubber elasticity equation. The inconsistence indicates that the calculated crosslinking densities are not comparable, possibly owing to their differences in the rigidity of polymer chains and intermolecular interaction.

A series of star-shaped block copolymers (CDPDPM) of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) with tunable stimuli-responsive behavior are synthesized via sequential atom transfer radical polymerization (ATRP) with the 2-bromoisobutyryl-terminated β-cyclodextrin (β-CD) as a core. The properties of these star-shaped copolymers are characterized by FT-IR, NMR and GPC analyses. Meanwhile, the thermo-sensitive behaviors of CDPDPM with different compositions and pH values are investigated by dynamic light scattering (DLS) and UV–vis measurements. The results have shown that the synthesized polymer CDPDPM exhibits both pH- and thermo-responsive behaviors in aqueous solutions. The star-shaped copolymers with the nearly equal mole fraction of DMAEMA and MEO2MA show two-step thermo-induced aggregation behavior in water at a pH near the isoelectric point (IEP), which corresponds to the formation of branch aggregates and large aggregates consisting of clustered branch aggregates, respectively. The mole fraction of DMAEMA and MEO2MA in polymer affects the thermal-responsive behaviors of polymer itself. Moreover, the micellar behaviors of the synthesized copolymers in aqueous solution are explored. The aggregation process of the copolymer can be generalized into intramolecular aggregation of the hydrophobic chains (corresponding to CI), formation of premicelles, the aggregation and rearrangement of the premicelles (namely CMC), as well as the formation of multicore structures. The CI and CMC values depend on both the MEO2MA molar fraction and the carbon backbone length of polymers. The aggregation number (N) and the sizes of polymer micelles (Dh) vary with the polymer composition, polymer concentration and ambient environment.

The traditional surfactant sodium dodecyl sulfate (SDS) and ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF4]) have been combined to create a novel efficient medium for chromogenic catalysis of 3,3′,5,5′-tetramethylbenzidine with horseradish peroxidase in presence of H2O2. The results have shown the [Emim][BF4] in the mediums can promote the rate of formation of the blue chromogen, the SDS is responsible for the stabilization of the blue chromogen due to the electrostatic attraction between positively charged blue chromogen and the negatively charged surfactant. The SDS/[Emim][BF4] combination not only enhance catalytic activity of HRP remarkably but also stabilize the blue chromogen formed in the HRP oxidation of the substrate TMB compared to the conventional medium. Based on the superior combination of SDS and [Emim][BF4], the colorimetric assay for detecting HRP activity and H2O2 concentration was established. This work demonstrates a novel efficient medium for chromogenic catalysis with potential applications in biosensors and clinical diagnosis.Download high-res image (196KB)Download full-size imageThe traditional surfactant sodium dodecyl sulfate (SDS) and ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF4]) have been combined to create a novel efficient medium for chromogenic catalysis of 3,3′,5,5′-tetramethylbenzidine (TMB) with horseradish peroxidase (HRP) in presence of hydrogen peroxide (H2O2). The SDS/[Emim][BF4] combination not only enhance catalytic activity of HRP remarkably but also stabilize the blue chromogen formed in the HRP oxidation of the substrate TMB compared to the conventional medium.

The interactions between poly(2-(2-methoxyethoxy)ethyl methacrylate90-co-oligo(ethylene glycol) methacrylate10) (P(MEO2MA90-co-OEGMA10)) and sodium dodecyl sulfate (SDS) or dodecyltrimethyl ammonium bromide (DTAB) in aqueous solutions with and without salt are explored. The influence rule of surfactant on thermo-sensitive behavior of polymer and the corresponding mechanism is revealed. The results have suggested that both surfactants have moderate interactions with P(MEO2MA90-co-OEGMA10), which result in the formation of P(MEO2MA90-co-OEGMA10)/surfactant complexes. Meanwhile, the self-aggregation of polymer chains is hindered causing the lower critical solution temperatures (LCSTs) increase due to the electrostatic repulsion and “locking water” effect caused by surfactant head groups. Tetra-n-butylammonium bromide (Bu4NBr) and tetra-n-propylammonium bromide (Pr4NBr) can associate with SDS and form mixed micelles. Interestingly, the formed mixed micelles apt to attach on the polymer chain and the polymer-bound necklace-like structure forms in the ternary polymer/salt/surfactant system. The structure of the complexes formed in the ternary system is confirmed by 2D NOESY NMR and the interaction mode is proposed. The relations between LCST of different systems and surfactant concentrations are also established quantitatively.

We report on the rheological behavior of wormlike micelles constructed by ionic liquid surfactant [C8mim]Br (1-octyl-3-methylimidazolium bromide) and anionic surfactant sodium oleate (NaOA) in aqueous solution. The effects of surfactant composition, total surfactant concentration, added salts, and temperature were investigated. The prevailing surfactant effect at lower concentration and the leading cosolvent effect at higher concentration of [C8mim]Br may be the main reasons for appearance of well-established maximum in key rheological parameters with variation of surfactant composition and total surfactant concentration. The Cole-Cole plots demonstrate that the systems (total surfactant concentration falls within 0.17–0.35 mol·L–1 and molar ratio 0.33≤R≤0.50) fit the Maxwell’s mechanical model as linear viscoelastic fluid. The addition of NaBr or sodium salicylate decreases significantly the viscosity and the relaxation time of the wormlike micelle solution but cannot change the value of plateau modulus G0. The present system has low rheological tolerance to temperature. The increase of temperature decreases the average contour length and viscosity of wormlike micelles and thus strengthens the relaxation progress of diffusion and weakens the relaxation progress of reptation. Increasing the temperature also decreases the value of plateau modulus G0 and shifts the minimum value of the loss modulus G″min to higher frequencies.

•Multiphase systems containing both surfactant and polymer were designed.•Liquid crystal is foundation of phase separation for system containing surfactant.•Zeta potential of existed phase determines whether the formation of new phase or not.•The different phases have different extraction powers to xylenol orange.A new phase separation system, aqueous multiphase system (MuPSs, ranging from two to four phases), containing surfactants and polymer (SDS/DTAB/PEG/NaBr/H2O) was designed and the complicated four-phase systems were investigated systematically. To interpret the phase separation phenomena, the phase composition, phase density, phase volume ratio between the studied phase and the whole system as well as the particle size and zeta potential of aggregates in each phases were investigated. The results have shown that the multiphase system contains liquid crystal phase, which may imply a close relationship between MuPSs and liquid crystal. At the same time, it seems there is a direct relationship between zeta potential of the existed phase and the appearance of new phase. Phase composition analysis results illustrate that the rich component for the three phases from top to the third one are PEG, DTAB, and SDS, respectively. However, the bottom phase is almost dilute brine. Furthermore, the differential scanning calorimetry experiments prove that the micro-complexity of aggregates in different phases is different from each other. The studied MuPSs are very stable but temperature sensitive; the coexisted phases have different extraction power to xylenol orange because of the variation of composition. The higher stability of MuPSs makes it useful when the storage and long-term stability of the separation media are important. The work not only provides theoretical guidance for the development of efficient extraction and separation technology but also provides new opportunities for the development of aqueous multiphase systems.A new phase separation system, aqueous multiphase system (ranging from two to four phases), containing surfactants and polymer (SDS/DTAB/PEG/NaBr/H2O) was designed, the multiphase systems are stable and different phases have different extraction powers to xylenol orange because of the variation of composition.

Interactions between ionic liquid surfactant [C12mim]Br and DNA in dilute brine were investigated in terms of various experimental methods and molecular dynamics (MD) simulation. It was shown that the aggregation of [C12mim]Br on DNA chains is motivated not only by electrostatic attractions between DNA phosphate groups and [C12mim]Br headgroups but also by hydrophobic interactions among [C12mim]Br alkyl chains. Isothermal titration calorimetry analysis indicated that the [C12mim]Br aggregation in the presence and absence of DNA are both thermodynamically favored driven by enthalpy and entropy. DNA undergoes size transition and conformational change induced by [C12mim]Br, and the charges of DNA are neutralized by the added [C12mim]Br. Various microstructures were observed such as DNA with loose coil conformation in nature state, necklace-like structures, and compact spherical aggregates. MD simulation showed that the polyelectrolyte collapses upon the addition of oppositely charged surfactants and the aggregation of surfactants around the polyelectrolyte was reaffirmed. The simulation predicted the gradual neutralization of the negatively charged polyelectrolyte by the surfactant, consistent with the experimental results.Graphical abstractHighlights► Aggregation of [C12mim]Br on DNA is led by electrostatic and hydrophobic interactions. ► Aggregation of [C12mim]Br is thermodynamically favored driven by enthalpy and entropy. ► DNA conformation and the charges carried by DNA can be modulated by [C12mim]Br. ► MD simulation emphasizes the interaction process and affirms the experimental results.

Decondensation of DNA molecules, previously compacted by cationic gemini surfactant 12-3-12 · 2Br, has been successfully achieved by introducing triblock copolymer (PEO)20–(PPO)70–(PEO)20 (P123). P123 can interact with 12-3-12 · 2Br to form supramolecular assemblies through hydrophobic interactions, while not interacting with DNA. When introducing 12-3-12 · 2Br into P123/DNA system, the presence of P123 will inhibit the formation of DNA/12-3-12 · 2Br complexes due to the stronger interaction between P123 and 12-3-12 · 2Br. For previously formed DNA/12-3-12 · 2Br complexes, the addition of P123 can lead to the release of DNA from the complex, which should be attributed to the complexation of P123 with free 12-3-12 · 2Br surfactants in bulk phase followed by the breakup of the thermodynamic equilibrium between surfactant aggregates associated with DNA and free surfactants in bulk phase. CD experiments reveal that 12-3-12 · 2Br can change the conformation of DNA from typical B-form to ψ-phase by formation of DNA/12-3-12 · 2Br complexes. However, the release of the surfactant from the complex induced by P123 turns DNA conformation from ψ-phase back to B-form.

The surface properties of mixed system containing gemini anionic surfactant 1,2,3,4-butanetetracarboxylic sodium, 2,3-didodecyl ester and partly hydrolyzed polyacrylamide were investigated by surface tension measurements and oscillating bubble methods. The influences of surfactant concentration, dilational frequency, temperature, pH, as well as salts on dilational modulus were explored. Meanwhile, the interfacial tension relaxation method was employed to obtain the characteristic time of surface relaxation process. The polymers play important roles in changing the interfacial properties especially at lower surfactant concentration. The possible mechanism of the polymer in changing the interfacial properties is proposed. Both the hydrophobic and electrostatic interaction among the surfactants and polymers dominate the surface properties of mixed system. These dynamic properties are of fundamental interest in understanding the structure of adsorption layers, dynamics of surfactant molecules, and their interaction with polymers at the surface.

The effect of hydrophilicity or hydrophobicity of polyelectrolyte on the interaction between polyelectrolyte and oppositely charged surfactants was investigated by using coarse-grained molecular dynamics simulations. The aggregation of surfactants on the hydrophilic polyelectrolyte is significantly different from that on the hydrophobic polyelectrolyte. The complexes evolve from the “bottle brush”, through the “necklace”, then to the micelle. However, the rod-like micelle, in which polyelectrolyte wraps around the micelle surface, only appears in the hydrophilic polyelectrolyte system. For the hydrophobic polyelectrolyte system, the spherical micelle is formed, and the polyelectrolyte penetrates into the hydrophobic core of complexes. The hydrophobic nature of the surfactant tails induces the surfactant’s tendency to depart from the hydrophilic polyelectrolyte and point toward the bulk phase, but it is apt to combine with the hydrophobic polyelectrolyte, leading to a parallel configuration between the surfactants and the polyelectrolyte. When the charge ratio (Z) of surfactant to polylelectrolyte is lower, the polyelectrolyte shows extended structure, and with the increase of Z, the polyelectrolyte collapse undergoes either a continuous or an abrupt change depending on if it is a hydrophobic or hydrophilic polyelectrolyte. At higher charge density of the hydrophilic polyelectrolyte, there is a synergistic effect of the electrostatic interaction between surfactant and polyelectrolyte, with the hydrophobic interaction among the adsorbed surfactants. For the hydrophobic polyelectrolyte system, no synergistic effect is observed.

The micellization of cationic gemini surfactant trimethylene-1,3-bis (dodecyldimethylammonium bromide) (12-3-12·2Br) was investigated and critical micelle concentrations (CMC) and thermodynamic parameters were evaluated as functions of ionic strength and temperature. The micellization of 12-3-12·2Br is entropically driven and thermodynamically favored. Raising the temperature slightly increases the CMC, while increasing the ionic strength lowers the CMC. A multi-technique study of the 12-3-12·2Br/DNA interaction and its dependence on ionic strength, temperature and DNA concentration were presented. DNA with loose coil conformation, necklace-like structure, highly ordered toroidal aggregates and coexisting of large aggregates and small structures in DNA/12-3-12·2Br system were observed. Critical aggregation concentrations (CAC), interaction saturation concentrations (C2), and associated thermodynamic parameters were determined. The screening effect of salt decreases the DNA/12-3-12·2Br electrostatic attraction, but favors the formation of free 12-3-12·2Br micelles or aggregates on the DNA chain. DNA acts as a separate phase contacting with the surfactant molecules and therefore CAC is independent of DNA concentration. Increasing DNA concentration postpones the appearance of free micelle in bulk phase, consequently increases the C2. Finally an interaction mechanism between 12-3-12·2Br and DNA was proposed.Graphical abstractComplex formation occurs at CAC, indicated by decrease of transmittance and ΔHobs. After C2, 12-3-12·2Br/DNA interactions reach saturation and free micelles emerge.Highlights► The micellization of 12-3-12·2Br is entropically driven and thermodynamically favored. ► Salt screens DNA/12-3-12·2Br electrostatic action but favors surfactant aggregation. ► DNA behaves as a separate phase so that the CAC is independent of DNA concentration.

The effect of added salts (NaCl, KCl and NaBr) on the aqueous two-phase system (ATPS) formed in mixtures of Gemini(12-3-12, 2Br−)/sodium dodecyl sulfate/polyethylene glycol has been investigated. Phase diagrams of the aqueous systems containing Gemini(12-3-12, 2Br−), sodium dodecyl sulfate (SDS), polyethylene glycol(PEG) and a salt have been determined experimentally at 313.15 K. The results indicate that the addition of salts not only induces the appearance of ATPS-A (in which anionic surfactant is in excess), shortens the phase separation time, enlarges the regions of ATPS-C (in which cationic surfactant is in excess), and decreases the minimum concentration required for forming an ATPS, but also alters the matching between anionic and cationic surfactants. Extractive experiments also showed that these salts notably enhance the extraction ability of ATPS; the Gemini-rich phase exhibits prominent cohesive action with xylenol orange, regardless of whether or not it is the upper phase or the lower phase.

The interaction of DNA with cationic gemini surfactant trimethylene-1,3-bis (dodecyl dimethyl-ammonium bromide) (12-3-12) and anionic surfactant sodium dodecyl sulfate (SDS) mixed system has been investigated by measuring the fluorescence, zeta potential, UV-Vis spectrum, and circular dichroism. In the absence of SDS, owing to the electrostatic and hydrophobic interactions, 12-3-12 forms micelle-like structure on the DNA chain before the micellization in bulk phase. For the mixed system of 12-3-12 and SDS, the negative charges on SDS can compete against DNA to bind with cationic 12-3-12 because of the stronger interaction between oppositely charged surfactants, and thus, the catanionic mixed micelles are formed before the formation of DNA/12-3-12 complexes. Thereafter, the positive charges on the mixed micelles bind with DNA, and thus, the change of the zeta potential from negative to positive is distinctly different from the system without SDS. Meanwhile, the existence of SDS postpones the exclusion of ethidium bromide (EB) from DNA/EB complexes. The conformation of DNA undergoes a change from native B-form to chiral ψ-phase as binding with 12-3-12 process. Upon adding SDS to the DNA/12-3-12 complex solution, however, DNA is released to the bulk and the ψ-phase returns to B-form again.