Surfactant-polymer interactions: Mixed micelles of hexadecylpyridinium bromide and trimethyltetradecylammonium bromide in aqueous poly(vinylpyrrolidone) solution

The conductance of hexadecylpyridinium bromide (HPyBr) and trimethyltetradecylammonium bromide (TTAB) mixtures over the entire mole fraction range of HPyBr (α_HPyBr) was measured in aqueous poly(vinylpyrrolidone) (PVP) solution containing 1, 5, and 10 wt% PVP at 30°C. Each conductivity curve showed two breaks corresponding to two aggregations throughout the whole mole fraction range of HPyBr and TTAB mixtures except for pure TTAB for which a single break corresponding to the conventional critical micelle concentration was observed. The two aggregation processes in the presence of low amounts of PVP were mostly similar to those in pure water, however, 10 wt% PVP shifted the break, corresponding to the second aggregation, toward the higher value. This was attributed to HPyBr/PVP interactions, which were also evident from the appearance of a second break in the conductivity (κ) plot of pure HPyBr in aqueous 10 wt% PVP. From conductivity data, various micellar parameters in the presence of PVP were determined and discussed from the standpoint of micelle-polymer interactions. The mixing behavior of HPyBr and TTAB corresponding to the first break in the presence of PVP was ideal for the most part and identical to that in pure water.     

Hydrophobic hydration of cationic mixed micelles by alkoxyethanols in aqueous media

The conductances of hexadecylpyridinium chloride (HPyCl) + tetradecyltrimethylammonium bromide (TTAB) mixtures over the entire mole fraction range of HPyCl (α_HPyCl) were measured in aqueous binary mixtures of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether containing 10 to 30 wt% additive in their respective binary mixtures at 30°C. Each conductivity curve showed a single break over the whole mole fraction range of HPyCl + TTAB mixtures. From the break in the conductivity curve, various micellar parameters were calculated and the results were discussed on the basis of alkoxyethanol's hydrophobic hydration of the mixed micelle. The micellar parameters of HPyCl, TTAB, and of their mixtures showed a strong dependence both on the amount and on the number of repeating units of ethylene and diethylene glycol derivatives. The hydrophobic hydration was considerably higher in the case of diethylene glycol derivatives owing to the presence of an extra ether oxygen. An evaluation of the non-ideality in the HPyCl + TTAB mixtures in the presence of additives revealed that alkoxyethanols reduce the unlike surfactant monomer interactions in order to form the mixed micelles in comparison to those in pure water. It has also been observed that such interactions systematically decrease with an increase in the number of repeating units from monomethyl ether to monobutyl ether, both in the case of ethylene and diethylene glycol derivatives.     

Polymer-Induced incompatibility in the mixed micelle formation of cationic surfactants with bulky polar head groups

The conductances of tetradecyltrimethylammonium bromide (TTAB)+tetradecyl triphenylphosphonium bromide (TTPB) mixtures over the entire mole fraction range were measured in aqueous poly(vinyl pyrrolidone) (PVP) containing 1 to 10 wt% of PVP at 30°C. Each conductivity (κ) curve showed a single break corresponding to the mixed micelle formation in the presence of PVP over the whole mole fraction range. From the conductivity data, various micellar parameters in the presence of PVP were computed and discussed in terms of micelle-polymer interactions. The mixing behavior of TTAB+TTPB in pure water was close to ideal, whereas in the presence of PVP a significant degree of nonideality was sobserved that was evaluated by computing the mole fraction of TTAB in the mixed micelle state (x ₁) and the interanction parameter (β) by using the regular solution approach. The former is less than the value in the ideal state, and the latter is much greater, indicating the enhancement in the antagonistic mixing behavior of TTAB+TTPB in the presence of PVP. The results have been explained on the basis of an increase in the incompatibility between the monomers of TTAB and TTPB in the mixed state due to the steric hindrances created by the PVP upon adsorption at the micelle-solution interface. The results have also been further supported by comparing with those of structurally similar cationic binary combinations in the presence of PVP.     

Interaction of tetradecyltrimethylammonium bromide with bovine serum albumin in different compositions: Effect of temperatures and electrolytes/urea

Herein, the interaction of a protein, bovine serum albumin (BSA), with tetradecyltrimethylammonium bromide (TTAB, a cationic surfactant), has been investigated using the conductivity measurement technique in pure water and some sodium salts (NaCl, Na₂SO₄, Na₂CO₃, and Na₃PO₄) solutions at temperature range of 295.15-320.15 K. Results reveal that, in the plot of specific conductivity versus the concentration of TTAB, only a single critical micelle concentration (cmc) was found for the TTAB + BSA mixed system in all solvents media studied. The addition of BSA in aqueous TTAB solution, the value of cmc undergoes a change from its pure form, which indicates the presence of strong interaction operating between the BSA and TTAB molecules. In aqueous system, the cmc values of the TTAB + BSA mixtures are obtained higher compared to the values found for single TTAB surfactant. However, the addition of salt decreases the cmc value of mixed TTAB + BSA system. The values of cmc of the BSA + TTAB mixed system at 310.15 K and 1.00 mmol·kg^-1 ionic strength of salt followed the order: cmc_Na2CO3 > cmc_Na3PO4 > cmc_NaCl > cmc_Na2SO4. The cmc values of TTAB + BSA mixture were found to be lowered in urea solution within the concentrations studied. The values of degree of dissociation (α) and fraction of counter ion binding (β) were found to be dependent on additives and temperature. The free energy of micellization (△G_m^o) is negative for all the systems, which manifests that the micellization phenomenon is energetically spontaneous. The enhancement of the negative value of △G_m^o in aqueous salt solutions reveals an increase of spontaneity of the TTAB + BSA micellization process. The values of △G_m^o also reveal that the spontaneity of micelle formation is enhanced at higher temperatures in all media studied. The values of free energy of transfer (△G_{m, t}^o) were also determined for numerous solvent media used in the present study and described with appropriate reasoning.     

Ionic liquids as catalytic additives for the acceleration of the photopolymerization of poly(ethylene glycol dimethacrylate)s

BACKGROUND: The fast development of practical applications of photopolymerizable compositions (PPCs) leads to a growing demand for the elaboration of novel monomers and simultaneously for the investigation of three‐dimensional polymerization mechanisms including the possible influence of initiator, additives, etc. The aim of the current study is to explore and clarify the role of ionic liquids (ILs) as environmentally friendly catalytic additives in the photopolymerization of poly(ethylene glycol dimethacrylate)s. RESULTS: The photopolymerization of triethylene glycol dimethacrylate (TEGDM) and poly(ethylene glycol‐400 dimethacrylate) (PEGDM) in the presence of various ILs both imidazolium‐based, i.e. [1‐methyl‐3‐alkylim]⁺ (CF₃SO₂)₂N^? (im = imidazolium; alkyl = C₂H₅, C₄H₉, C₁₄H₂₉), and phosphonium‐based, i.e. [P⁺ (C₆H₁₃)₃(C₁₄H₂₉)]X^? (X^? = PF₆^?, BF₄^?, (CF₃SO₂)₂N^?, Cl^?), as catalytic additives was investigated. The influence of the concentration of the ionic salts as well as the nature of the ILs upon the photopolymerization was studied in detail. It was found that imidazolium ILs accelerate TEGDM photopolymerization and suppress the polymerization of PEGDM. In contrast, polymerization of PEGDM with extra small amounts of phosphonium ionic solvents proceeded at a high rate and offered access to new polymers and the utilization of low‐reactivity monomers in PPCs. CONCLUSION: The most striking advantage is that the use of certain ILs permits the control of polymerization rate to achieve maximum oligomer conversion. Copyright © 2007 Society of Chemical Industry     

Effect of additives on the clouding behavior of sodium dodecyl sulfate + tetra-<Emphasis Type="Italic">n</Emphasis>-butylammonium bromide system

The effect of additives on the cloud point (CP) of nonionic surfactants has been studied for more than six decades. Ionic surfactants, however, generally do not show clouding. Recently, CP in ionic surfactant solutions have been reported in the presence of a few quaternary bromides. In this study, we report the effect of various additives (e.g., ureas, sugars, salts, organic solvents, acids) on the CP of sodium dodecyl sulfate (SDS) + tetra-n-butylammonium bromide (Bu₄NBr) systems. An increase in CP of the system with urea concentration is explained by its water structure-breaking ability. An opposite effect of thiourea may be due to the direct interaction of the compound with the SDS-Bu₄NBr mixed micelle. The CP-decreasing effect of sugars is due to their water structure-making ability. All the salts decrease the CP, owing to increased counterion binding. The organic solvents used here raise the CP, whereas the other organic additives decrease the CP. The overall criteria of CP variation seemingly depend upon the solubilities of the additive in the micellar interfacial region and the background solvent.     

Microwave dielectric relaxation and molecular dynamics in binary mixtures of poly(propylene glycol) 2000 and poly(ethylene glycol)s of varying molecular weight in dilute solution

Molecular dynamics of binary mixtures of poly(propylene glycol) (PPG) and poly(ethylene glycol)s (PEGs) of varying molecular weight due to molecular interactions, chain coiling and elongation in dilute solution under various conditions, ie varying number of monomer units of PEG, method of mixing of polymers and solvent environment, has been explored using microwave dielectric relaxation times. The average relaxation time τ_o, relaxation time corresponding to segmental motion τ₁ and group rotations τ₂, of a series of binary mixtures of poly(propylene glycol) 2000 and poly(ethylene glycol) of varying molecular weight (ie PPG 2000 + PEG 200, PPG 2000 + PEG 300, PPG 2000 + PEG 400, and PPG 2000 + PEG 600 mixed by equal volume in the pure liquid states, and PPG 2000 + PEG 1500, PPG 2000 + PEG 4000 and PPG 2000 + PEG 6000 mixed equal weights in solvent) have been determined in dilute solution in benzene and carbon tetrachloride at 10.10 GHz and 35 °C. A comparison of the results of these binary systems of highly associating molecules shows that the molecular dynamics corresponding to rotation of a molecule as a whole and segmental motion in dilute solutions are governed by the solvent density when the solutes are mixed in their pure liquid state. Furthermore, the molecular motion is independent of solvent environment when the polymers are added separately in the solvent for the preparation of binary mixtures. It has also been observed that there is a systematic elongation of the dynamic network of the species formed during mixing of pure liquid polymers in lighter environment of solvent with increasing PEG monomer units, while the elongation behaviour of the same species in the heavier environment of carbon tetrachloride solvent is in contrast to the elongation behaviour of the polymeric species formed in pure PEG. The role of rotating methyl side‐groups in the PPG molecular chain has been discussed in term of the breaking and reforming of hydrogen bonds in complex polymeric species for the segmental motion. In all these mixtures, the relaxation time corresponding to group rotations is independent of the solvent environment and constituents of the binary mixtures. The effect of chain flexibility and coiling in these binary mixtures is discussed by comparing the relaxation times of the mixtures with their individual relaxation times in dilute solutions measured earlier in this laboratory. © 2001 Society of Chemical Industry     

Micellar association in simultaneous presence of organic salts/additives

Viscosity measurements under Newtonian flow conditions had been performed on cetyltrimethylammonium bromide (CTAB) aqueous solutions in the combined presence of sodium salts of aromatic acids (sodium salicylate, NaSal; sodium benzoate, NaBen; sodium anthranilate, NaAn) and organic additives (1-hexanol, C₆OH; n-hexylamine, C₆NH₂) at 30°C. On addition of C₆OH or C₆NH₂, the viscosity of 25 mM CTAB solution remained nearly constant without salt as well as with a lower salt concentration. This is due to low CTAB concentration which is not sufficient to produce structural changes in this concentration range of salts. However, as the salt concentration was increased further, the effect of C₆OH/C₆NH₂ addition was different with different salts: The viscosity first increased; then a decrease was observed with the former while with C₆NH₂ a decrease followed by constancy appeared in plots of relative viscosities (η _r ) vs. organic additive concentrations. At further higher salt concentration, the magnitude of η _r was much higher. The viscosity increase is explained in terms of micellar growth and the decrease in terms of swollen micelle formation (due to interior solubilization of organic additive) or micellar disintegration (due to formation of water + additive pseudophase).     

Effects of 1-Alkyl-(and 1-Benzyl)-2,3-Dimethylimidazolium Ionic Liquids as Additives on the Micellar Behavior of Surfactant SB-12

The micellization and surface-active behavior of zwitterionic surfactant N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SB-12) in aqueous media were investigated in the absence and presence of different alkyl-appended and benzyl-appended ionic liquids (IL) 1-butyl-2,3-dimethylimidazolium chloride [bdmim][Cl], 1-butyl-2,3-dimethylimidazolium bromide [bdmim][Br], 1-hexyl-2,3-dimethylimidazolium bromide [hdmim][Br], and 1-benzyl-2,3-dimethylimidazolium chloride [bzdmim][Cl]. The characteristics of self-organization processes in SB-12 + IL/water systems include critical micelle concentration (cmc), aggregation number (N_agg), micellar size (D), surface, and adsorption parameters. These parameters were determined by the fluorescence and surface tension measurements. In SB-12 solutions, cmc were found to be decreasing to different extents in the presence of all the studied IL than in pure water. The addition of IL [hdmim][Br] decreases the cmc of aqueous SB-12 to rather a low extent. The other three IL show a prominent lowering in cmc of surfactant SB-12 to different magnitude. The maximum lowering in cmc was observed due to addition of benzyl-appended IL [bzdmim][Cl]. The aggregation number of aqueous SB-12 solution obtained in general is higher at high wt.% of added IL. The average micellar size was also found to increase upon addition of IL. Both IL anions and cations interacted with the charged centers present on the zwitterionic surfactant SB-12, which caused a substantial increase in the surface activity.     

The Effect of Ethanol on Nanostructures of Mixed Cationic and Anionic Surfactants

Micellization of tetradecyl trimethyl ammonium bromide (TTAB) and sodium dodecyl sulfate (SDS) in water–ethanol (ET) micellar solutions, with the weight percent of ET changing within the range 0–30, was studied by means of surface tension and conductivity measurements. Surface tension measurements also provided information about the dependence of the surface excess concentration, the minimum area per surfactant molecule, and the standard Gibbs energy of adsorption on the added weight percent of the organic solvent. Information about the degree of counterion dissociation and phase transition was obtained through conductivity measurements. Cyclic voltammetry (CV) and dynamic light scattering (DLS) was also employed to investigate the mixed micellar behavior of the binary mixtures. It was shown that an excess of cationic surfactant and ET resulted in a phase transition of vesicles and large micelles to mixed micelles. The regular solution theory approximation was used to determine various micellar parameters of ideal systems. The regular solution interaction parameter (β) suggests that the formation of mixed micelles is due to the synergistic interactions in the case of TTAB/SDS systems and becomes affected by the water/ET ratio.     

Synthesis, Antimicrobial Activity and Micellization of Gemini Anionic Surfactants in a Pure State as Well as Mixed With a Conventional Nonionic Surfactant

New gemini anionic surfactants were prepared from sodium salts of monoalkyl sulfosuccinate esters of ethylene glycol having variably long tails (C₁₂, C₁₆, C₁₈) and dichloroethane. The chemical structures of the prepared surfactants were confirmed using different spectroscopic techniques. The surfaces tension values of the synthesized surfactants were measured at 25 °C individually or mixing at different molar fractions with ethoxylated alkylphenol. In all cases, mixed micellar aggregates were formed and critical micellar concentrations of binary mixtures containing different mole fractions of the surfactants were measured. The micellization processes of the individual and mixed surfactants were investigated. The effect of different alkyl chains of gemini anionic surfactants on properties of binary systems and molar ratio in the mixed aggregates were deduced. The critical micelle concentration of mixed surfactants shifted to lower values compared to those of the single surfactants. Effectiveness values increased with decreases in the mole fraction of gemini anionic surfactants. The negative values of interaction parameter (β) increased with increases in the chain length of anionic surfactants. The activity coefficient (f ₁, f ₂) and total minimum surface area of mixed solution were calculated. Also, the gemini anionic surfactants prepared have moderate antimicrobial activity towards bacteria and not active towards fungi.     

Properties of aqueous solutions for two binary mixed systems between two kinds of bile salts and nonionic surfactants

The micellar properties of aqueous binary mixed solutions for two systems consisting of sodium cholate (NaC)-octaoxyethylene glycol mono n-decyl ether (C₁₀E₈) and sodium glycocholate (NaGC)-C₁₀E₈ have been studied on the basis of surface tensions, polarity of the micelle interior and the mean aggregation number. Application of two theoretical treatments, based on regular solution and excess thermodynamic quantities for critical micellar concentration (CMC) data from surface tension curves of two mixed systems showed that the mole fraction of each bile salt in the mixed micelles near the CMC is lower than that of the corresponding prepared mole fraction in the mixed solution. The polarity of the interior suggested that the hydrophobicity of intramicelles increased with the increase of the mole fraction of bile salt in the mixed solution and that the mixed micelles become dramatically more hydrophobic at a mole fraction of 0.68 for NaGC−C₁₀E₈ system and 0.75 for NaC−C₁₀E₈ system, respectively. This implies that the micelles become richer in the bile salt molecules and the tendency appears strongly for NaGC−C₁₀E₈ system due to the strong cohesion between the conjugated glycines in the NaGC molecules. The decrease of aggregation number with the increase of the mole fraction of bile salts shows that the micelles approach those of the single system of each bile salt. This supports the previously mentioned facts.     

Self-Assembly,Surface Activity and Structure of n-Octyl-β-D-thioglucopyranoside in Ethylene Glycol-Water Mixtures

The effect of the addition of ethylene glycol (EG) on the interfacial adsorption and micellar properties of the alkylglucoside surfactant n-octyl-β-d-thioglucopyranoside (OTG) has been investigated. Critical micelle concentrations (cmc) upon EG addition were obtained by both surface tension measurements and the pyrene 1:3 ratio method. A systematic increase in the cmc induced by the presence of the co-solvent was observed. This behavior was attributed to a reduction in the cohesive energy of the mixed solvent with respect to pure water, which favors an increase in the solubility of the surfactant with EG content. Static light scattering measurements revealed a decrease in the mean aggregation number of the OTG micelles with EG addition. Moreover, dynamic light scattering data showed that the effect of the surfactant concentration on micellar size is also controlled by the content of the co-solvent in the system. Finally, the effect of EG addition on the microstructure of OTG micelles was investigated using the hydrophobic probe Coumarin 153 (C153). Time-resolved fluorescence anisotropy decay curves of the probe solubilized in micelles were analyzed using the two-step model. The results indicate a slight reduction of the average reorientation time of the probe molecule with increasing EG in the mixed solvent system, thereby suggesting a lesser compactness induced by the presence of the co-solvent.     

Micellization Behavior of Cationic Gemini Surfactants in Aqueous-Ethylene Glycol Solution

The micellization behavior of gemini surfactants i.e. alkanediyl-α,ω-bis(cetyldimethylammonium bromide) (C₁₆-s-C₁₆,2Br⁻ where s = 3, 4, 10) in 10% (v/v) ethylene glycol solution was investigated by surface tension and conductometric measurements at 300 K. The critical micelle concentration, degree of micellar ionization, surface excess concentration, minimum surface area per molecule of surfactant, surface pressure at the CMC and Gibbs energy of adsorption of the dimeric surfactants have also been determined in the presence of different salts (NaCl, NaBr and NaI). The critical micelle concentration and degree of micellar ionization values decrease significantly in the presence of sodium halides and follows the sequence NaCl < NaBr < NaI. The free energy, enthalpy and entropy of micellization of dimeric surfactants in 10% (v/v) ethylene glycol solution were determined using the temperature dependence of the critical micelle concentration. The standard free energy of micellization was found to be negative in all the cases.     

Solution thermodynamic study of several hydrocarbons in γ-butyrolactone and ethylene glycol mixtures by GLC

The gas—liquid chromatographic technique was used to determine the thermodynamic properties of solutions at infinite dilution for binary and ternary systems of five normal paraffins (C₅–-C₉), cyclohexane, benzene and toluene with γ-butyrolactone and ethylene glycol mixtures. A combination solvent of 50 mol % of γ-butyrolactone and ethylene glycol was shown to have the highest selectivity towards aromatic hydrocarbons.     

Micellar and Surface Properties of Some Monomeric Surfactants and a Gemini Cationic Surfactant

The physicochemical and interfacial properties of the monomeric surfactants cetyltrimethyl ammonium bromide (CTAB), cetyltriphenyl phosphonium bromide (CTPB), tetradecyl triphenyl phosphonium bromide (TTPB), cetyldiethylethanol ammonium bromide (CDEEAB), cetyltrimethyl ammonium chloride (CTACl), tetradecyltrimethyl ammonium bromide (TTAB), and a gemini surfactant (C₁₆-3-C_16, 2Br⁻) at different pH (3.1, 7.0, and 7.75) have been investigated by conductivity and surface tension measurements at 300 K. The critical micellar concentration (CMC), degree of micellar ionization (α), surface excess concentration (Г_max), minimum surface area per molecule of surfactant (A _min), Gibbs free energy of micellization (∆G _m⁰), surface pressure at the CMC (π _CMC), and the Gibbs energy of adsorption (∆G _ads⁰) of the monomeric surfactants have also been determined. The CMC, α and Г_max, increase with increasing pH whereas A _min decreases.     

Aggregation and adsorption behavior of cobalt-based metallosurfactant in water–ethylene glycol media forming worm-like micelles

The cobalt based metallosurfactant cis-chlorobis(ethylenediamine)hexadecylaminecobalt(III) chloride (CHCC) has been prepared and well characterized by utilizing elemental analysis, NMR (¹H, ¹³C), FT-IR and UV–Vis spectroscopy. The CHCC metallosurfactant shows thermal stability up to 168°C. The micellization behavior of the synthesized CHCC metallosurfactant has been investigated systematically by the tensiometric, conductometric, and fluorescence techniques. The critical micelle concentration (cmc) values of CHCC have been determined in various water–ethylene glycol mixtures ranging from 0 to 100 weight % of ethylene glycol at 293.15, 298.15, 303.15, and 308.15 K. The physicochemical parameters namely counterion binding constant, surface pressure, surface excess, surface area covered per CHCC metallosurfactant molecule, free energy minimum, standard free energies of micellization and adsorption, standard enthalpy and entropy of micellization, and Gibb's free energy of transfer have been calculated. The hydrodynamic diameters and zeta potentials of the CHCC metallomicelles have been measured by dynamic light scattering method. Transmission electron microscopy was employed to confirm the presence of worm-like micelles.     

Solubilization of cholesterol in two binary mixed micelles of bile salt and nonionic surfactant

The saturated amounts of solubilized cholesterol (C_ch) in mixed micelles of sodium cholate (NaC) and octaoxy-ethylene glycol monon-decyl ether (C₁₀E₈) and of sodium zyme assay at 25, 29, 33 and 37°C. The C_ch values in both systems increase with the total surfactant concentration. Because the mixed micelles for both systems tend to form C₁₀E₈-rich micelles near the critical micellar concentration (CMC) of the mixed system, the curves of cholesterol solubility approached the C_ch curve for C₁₀E₈ alone near the CMC. The tendency of C_ch to decrease in both systems with increasing mole fractions of bile salts resembled that of the mean aggregation number of micelles. Thermodynamic analyses of cholesterol solubilization showed that the free energy of solubilization, if considered as the transfer of cholesterol from solid state to micellar environment, increased with increasing mole fraction of bile salt. The enthalpy of cholesterol solubilization (ΔH_S→M) decreased with the mole fraction of bile salts and showed break points around the mole fraction of 0.75 for the NaC−C₁₀E₈ system and at 0.60 for the NaDC−C₁₀E₈ system, respectively. These phenomena resemble earlier hydrophobicity data for mixed micelles by fluorescence measurements. Furthermore, C_ch values for the NaDC−C₁₀E₈ system were larger than those for the NaC−C₁₀E₈ system because of the structural differences at the 7α hydroxyl group between NaC and NaDC. This fact was confirmed by thermodynamic calculations.     

Micellization of a di‐block copolymer in ethylene glycol and its utilization for suspension of carbonaceous nanostructures

Suspensions of carbonaceous nanoparticles (NPs) in ethylene glycol (EG) can be used as colloidal inks for additive manufacturing and nano‐fluids for heat‐transfer applications. While micellar solutions of surfactants are often used for suspension of the NPs in water, micellization of surfactants in EG is suppressed as compared to aqueous solutions and a well‐defined critical micellization concentration (CMC) is often not observed. Unlike the surfactants, a di‐block copolymer comprising a poly(ethylene glycol) monomethylether methacrylate (PEGMA) segment, 2‐(diethylaminoethyl) methacrylate (DEAEMA) and butyl methacrylate (BMA), poly(O950)‐b‐(DEAEMA‐co‐BMA) was found to assemble into spherical micelles in EG. Surface tension measurements show a well‐defined CMC that depends on the volume fraction of EG. Cryogenic transmission electron microscopy and dynamic light scattering show the presence of spherical micelles with a diameter that reduces with the volume fraction of EG. The micellar solutions were further used for suspending carbonaceous NPs of different geometry and characteristic dimensions: C₆₀ fullerenes, multi‐walled carbon nanotubes, and nanodiamonds. The flow behavior of the suspensions exhibits a relatively low viscosity and mostly Newtonian behavior due to strong interaction between the NPs and the micelles. These suspensions may be used as colloidal inks for two‐dimensional and three‐dimensional printing. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46518.     

Organic Additives and Electrolytes as Cloud Point Modifiers in Octylphenol Ethoxylate Solutions

Cloud point measurements of nonionic surfactant Triton X-100, an octylphenol ethoxylate, were carried out in the absence and presence of various organic additives such as n-alkanols (methanol, ethanol, propanol and butanol), glycols (ethylene glycol, diethylene glycol and triethylene glycol), glycol ethers (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol monobutyl ether (EGMBE)) and electrolytes (LiCl, KCl, NaF, NaCl, NaBr, NaI, MgCl₂ and AlCl₃). The combined effect of these organic additives and electrolytes on cloud point (CP) measurement was also investigated. The effect of nature of cation, anion and valency of cation on CP is also reported. Among the n-alkanols and glycol ethers as additives, n-butanol and EGMBE were found to decrease the CP while all other additives increase the cloud point. The addition of electrolytes (LiCl, NaCl and KCl) to the solution of Triton X-100 (TX-100) decreases the CP but the rate of decrease in CP with concentration does not follow the lyotropic series of effect. Sodium halides (except NaI) also decrease the CP and the rate of decrease follows the lyotropic series of effect even in the presence of organic additives. NaI is a water structure breaker, hence it increases the cloud point. Further, cations of increasing valency lessen the depression in CP of TX-100 with the rate of decrease in CP following the order Na⁺ > Mg²⁺ > Al³⁺ even in the presence of organic additives.