Cloud Point Of Aqueous Solution Research Articles

Effect of Molecular Weight on Cloud Point of Aqueous Solution of Poly (ethylene oxide)-Poly (propylene oxide) Alternating Multiblock Copolymer.

A poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO) alternating multiblock (AMB) copolymer with various molecular weights was prepared via precipitation fractionation from an acetone/n-hexane mixture. The cloud point (Tc) of the aqueous solution of PEO-PPO AMB copolymer decreased as the number-average molecular weight of the sample increased. This phenomenon is generally observed for certain homopolymer systems having a lower critical solution temperature, such as PEO/water and poly(N,N-diethylacrylamide)/water systems. The relationship between the Tc of the solutions and the number of monomer units of the AMB copolymer suggests that the Shultz-Flory theory is applicable to this system.

The cloud point of aqueous solutions of ethoxylated monoalkylphenols in the individual state and in the presence of electrolytes

ABSTRACTThe cloud points tcp of aqueous solutions of ethoxylated monoalkylphenols, AF9-n (n = 8,9,10,12), were measured in the concentration (C) range of 0.25-40 wt.%. tcp increased as C decreased at C < 1 wt.%. At 1 < С < 10 wt.%, tcp changed insignificantly; Δtcp/tcp did not exceed 5%. Solutions transformed into the gel state at С > 10-20 wt.% and tcp sharply increased. The dependence of tcp on the length of the oxyethylene chains of ethoxylated nonylphenols at C = 1 wt.% can be described by the equation tcp = b·ln(n-n0), where n0 = 6. The cloud points of aqueous solutions (C = 1 wt.%) of the ethoxylated nonylphenols were measured at different concentrations of NaI, NaCl, NaF, Na2CO3, and Na2SO4 salts. For all of these solutions, tcp decreased in the presence of NaCl, NaF, Na2CO3, Na2SO4 and increased in the presence of NaI. To describe the dependence of tcp on the salt concentration, the equation was suggested, where and tcp are the cloud points of a neat aqueous solution of ethoxylated nonylphenols and of the solution in the presence of electrolytes, respectively.

Density, Surface Tension, and Cloud Point of Aqueous Solutions of β-Cyclodextrin-polyethylene Glycol

The physical property data (density, surface tension, and cloud point) for aqueous solutions of β-cyclodextrin-polyethylene glycol have been determined at temperatures from (293.15 to 313.15) K and atmospheric pressure. Results show that the density and surface tension decrease as the temperature increases. The density and cloud point increase with the mass fraction of β-CD-PEG, whereas the surface tension decreases. Finally, the density and surface tension experimental data have been correlated with different equations. Specifically, the density increases linearly with the increase of β-CD-PEG mass fraction from 2 % to 10 %; however, the surface tension of β-CD-PEG decreases quickly in the β-CD-PEG mass range of 0.001 % to 0.060 %. When the β-CD-PEG mass fraction is 0.080 % the surface tension of β-CD-PEG shows the minimum value, 56.1 mN·m–1.

The polydispersity effect of distributed oxyethylene chains on the cloud points of nonionic surfactants

The cloud points of aqueous solutions containing polyoxyethylene surfactant molecules with a distribution of chain lengths were studied for several nonionic surfactants. Experimentally, the cloud points increased as the oxyethylene chain lengths increased with a linear or logarithmic relation of the number of oxyethylates, as proposed by Schott. An experimental scale, the p-Po scale, was previously developed to correspond to the cloud points, where p is the average number of oxyethylene units per molecule and Po is the shortest chain length reference. However, no previous prediction methods of cloud point addressed systems containing a range of chain lengths. In this work, we propose a rescaling of the representative chain length as s-Po, where s is the cloud point-weighted mean ethylene oxide chain below p, and approximated as (p-Po)/PDI where PDI is the polydispersity index. Using the rescaled length, the experimental data for C(12)Es (lauryl alcohol ethoxylate, LAE), NPE-10 (nonyl phenol ethoxylate) and TDE-10 (tridecyl alcohol ethoxylate) were successfully predicted with no additional parameters, such as {(p-Po)/(PDI)}/CP=a+b{(p-Po)/(PDI)}, where PDI indicates the Broadness of the chain length distribution.

Temperature Sensitivity Control of Alkylamide-Terminated Poly(amidoamine) Dendrimers Induced by Guest Molecule Binding

We examined the effect of binding of rose bengal (RB) to alkylamide-terminated PAMAM G5 dendrimers on their temperature-sensitive properties. The cloud point of aqueous solutions of the isobutyramide-terminated dendrimer decreased with increasing amount of RB molecules bound to the dendrimer. The propylamide-terminated dendrimer, which is fundamentally temperature-insensitive, also exhibited a cloud point after binding of RB. Results indicate that complexation with guest molecules might be an efficient approach for control of temperature sensitivity or even temperature sensitization of dendrimers.

Oxo-Alcohol Ethoxylates: Surface and Thermodynamic Properties and Effect of Various Additives on the Cloud Point

AbstractIn this study the thermodynamic properties of various Oxo-alcohol ethoxylates related to their adsorption at the air/water interface and to their micellization have been studied. The effect of various additives, including electrolytes, alcohols, polar aromatic solutes, and ionic and nonionic surfactants on the cloud point of aqueous solutions of the same surfactants has also been investigated. Salting-out electrolytes lower the cloud point while salting-in species raise it. Except for the totally water-miscible alcohols, most hydroxylated compounds lower the cloud point. Phenols, aromatic alcohols, and amines seem to interact preferentially with the ethylene oxide groups of the micelles, leading to strong dehydration, and consequently lowering the cloud point. On the contrary, by forming mixed micelles, an anionic surfactant strongly raises the cloud point of the nonionic.

Surfactants and interfacial phenomena

Surfactants and interfacial phenomena

Cloud Point of Aqueous Solutions of Tetrabutylammonium Dodecyl Sulfate Is a Function of the Concentration of Counterions in the Aqueous Phase

The cloud point of the surfactant tetrabutylammonium dodecyl sulfate is shown to be a function of the tetrabutylammonium counterion concentration in the aqueous phase whether the counterions are provided by the surfactant or both the surfactant and added tetrabutylammonium bromide. The micellized surfactant dissociates 17% of its counterions to aqueous phase.

Cloud point of aqueous solutions containing oxyethylated methyl dodecanoates: effects of surfactant hydrophilicity, nature of added electrolyte, and water activity

The aim of this work was to determine the cloud points of new oxyethylated methyl dodecanoates of various hydrophilicity (OMD- n, where n refers to the average degree of oxyethylation) and to correlate them with surfactant hydrophilicity and, for a given electrolyte, with water activity. Thus, it is shown that the cloud point in the absence of electrolyte (CP 0) can be simulated by the following equation: CP 0=165.5log n−112.0 (with R 2=0.987). The effects of NaCl, NaHCO 3, and KSCN on the cloud point are also reported and discussed. The salting-out effect arising from the presence of NaCl or NaHCO 3 is explained by the existence of a hydration shell with enhanced water structure as well as a zone with decreased salt concentration around the (OCH 2CH 2) n  chain, as compared with the bulk. On the other hand, the salting-in effect is explained by depletion of water around the (OCH 2CH 2) n  chain. Thus, it is estimated that the number b of water molecules forced back into the bulk solution from the salt-deficient regions when the hydration shells of two OCH 2CH 2 monomer units overlap ranges between 2 and 3 and 3 and 4 for NaCl and NaHCO 3, respectively, depending on the average degree of oxyethylation n of OMD- n. It is also shown that the water activity is a useful parameter to simulate the variation of cloud point in the presence of an electrolyte (CP) at low and moderate concentration (e.g., <1 M NaCl), CP 0/CP≈1−( bR/ α)ln a w , where R is the gas constant and α≈15 J K −1 mol −1. At high electrolyte concentration, the relationship between CP 0/CP and ln a w significantly deviates from linearity. In the particular case of KSCN, an inversion of the salt effect can be observed. The salting-in effect of KSCN increases up to about 2 M, but decreases at higher KSCN concentrations, so that KSCN can even act as a salting-out salt at high concentration (typically above 3.3 M for OMD-14).

The effect of electrolytes on the cloud point of poly ethylene glycol aqueous solutions

Cloud points of aqueous solutions of poly ethylene glycol (PEG)/inorganic salts are measured using the particle counting method. The average molecular weights of PEG are 3,350 and 10,000. NaH2PO4, Na2HPO4, KH2PO4 and K2HPO4 are the inorganic salts used. Measurements are done for different weight percentage of PEG and salts in water.

Synthesis of novel cationic polymeric surfactants

A series of new cationic polymeric surfactants, comprising a short hydrophobic n-alkyl (C12 or C16) end-group and a long hydrophilic sequence of 17–68 2-(dimethylamino)ethyl methacrylate (DMA) units, were successfully synthesized by oxyanion-initiated polymerization. A previously titrated solution of DMSO−K+ was used for quantitative formation of the potassium alcoholate initiators from the corresponding C12 or C16 alcohols. Optimum polymerization conditions were found to be at or above room temperature, using THF as solvent. Under these conditions the polymers had relatively narrow polydispersities (Mw/Mn≈1.25) and both GPC and NMR spectroscopy showed no residual monomer. NMR studies of the surfactants in CDCl3 also confirmed that good control over the degree of polymerization was achieved, indicating very high initiator efficiency. Cloud points of aqueous solutions of selected polymeric surfactants were determined by turbidimetry and decreased with increasing DMA chain length, as expected.NMR spectra of the surfactants were also recorded in D2O. The C12 surfactants each had roughly the same degree of polymerization of DMA in D2O as that obtained in CDCl3, suggesting molecular dissolution. In contrast, the apparent degrees of polymerization for the DMA blocks in the C16 surfactants were markedly higher in D2O than in CDCl3. This indicates reduced solvation for the C16 moiety, which is consistent with micelle formation. Surface tensiometry studies indicated higher surface activities for the C12-based surfactants compared to the C16-based surfactants. Again, this is consistent with the hypothesis that the latter surfactants form intermolecular micelles in aqueous solution, whereas the C12-based surfactants are molecularly dissolved. Dynamic light scattering and transmission electron microscopy studies confirmed the existence of micelles in C16 surfactant solutions but no micelles were observed for the C12 surfactants. Finally, a selectively deuterated C12-based polymeric surfactant was also prepared for planned neutron reflectivity studies at the air–water interface.

Effect of Additives on the Cloud Points of Aqueous Solutions of Ethylene Oxide–Propylene Oxide–Ethylene Oxide Block Copolymers

The cloud points of aqueous solutions of eight ethylene oxide (EO)/propylene oxide (PO) triblock copolymers were measured in the presence of eight additives. The additives increased these temperatures in the following sequence: urea, dimethylurea, tetrapropylammonium bromide < nicotinamide < sodium thiocyanate < sodiump-toluenesulfonate < sodium xylenesulfonate < tetrabutylammonium bromide. No similar trend could be derived in relation to the polymers structure or composition. The same additives were tested with two ethoxylated nonylphenols and with three PPO and were only effective to increase the cloud points of compounds containing EO chains. This observation suggests that these additives affect the solvation capacity of water in relation to the EO units, especially at higher temperatures.

Preparation of poly(vinyl alcohol) as the dispersant for suspension vinyl chloride polymerizations

The study of the influence of the reaction conditions of alkaline catalysed methanolysis or hydrolysis of methanolic poly(vinyl acetate) (PVAc) solution shows that for PVAc with an average degree of polymerization of ∼1140 the optimal degree of hydrolysis for use as a dispersant in the suspension polymerization of vinyl chloride is ∼71 mol%. Also, the cloud point of aqueous solutions with 1 wt% poly(vinyl alcohol) (PVA) is at 23–29°C. It is necessary to minimize the amount of water present during PVAc methanolysis. PVA samples produced under optimal conditions can be used as dispersants for the suspension polymerization of vinyl chloride.

Incorporation of hydrocarbons into surfactant monolayers

Alkane incorporation into close-packed surfactant monolayers at oil-water interfaces can greatly influence the surface concentration of surfactant, depending on the chain length of the alkane. Such incorporation into monolayers stabilising microemulsion droplets in Winsor systems (microemulsions in equilibrium with excess of the dispersed phase) can cause an inversion of the microemulsion type from oil-in-water to water-in-oil or vice versa. Closely related to this are the effects which solubilised hydrocarbon can have on the cloud points of aqueous solutions of nonionic surfactants. It is difficult to measure quantitatively the extent of hydrocarbon incorporation into surfactant monolayers at oil-water interfaces, but we have determined the extent of uptake of a range of alkanes into monolayers of various surfactants at the air-water surface. In this paper we consider close-packed monolayers at both planar and curved (microemulsion droplet) interfaces, and the effects which incorporation of hydrocarbons into the monolayers has on system behaviour. The extent to which mixed alkane+surfactant monolayers resemble monolayers at oil/water interfaces is explored, and for one system we show how alkane incorporation into films at A/W surfaces directly mirrors microemulsion behaviour in the same system.

Lower critical solution temperature (LCST) and theta temperature of aqueous solutions of nonionic surface active agents of various polyoxyethylene chain lengths

Cloud points of aqueous solutions of homogeneous poly(oxyethylene)dodecyl ether derivatives (C12(OE)n: n=2–8) and the apparent theta temperatureTθ ap were determined from the abrupt changes in optical transmittance and the temperature dependence of the second virial coefficient obtained by light scattering measurements. It was found that the lower critical solution temperature (LCST) shifts to a lower temperature and lower concentration as the number of oxyethylene units in a molecule decreases. Because of this behavior of LCST, the modified Flory-Schultz plot of phase separation was applied to the present nonionic surfactant-water system, and its theta temperature obtained. The dependence ofTθ ap on the number of oxyethylene units suggests that the polyoxyethylene chain has different effects on the solubility of C12(OE)n in water forn less than or equal to 3 from those forn greater than or equal to 4.

EVALUATION OF EMULSIFIER BLENDING

ABSTRACT The mechanism of emulsifier blending of different hydrophile-lipophile balance has been studied by the measurements of 1) the phase inversion temperature ( PIT) in emulsions, 2) the size distribution of droplets and the stability of emulsions, and 3) the cloud points of aqueous solutions. The PIT was slowly depressed with the replacement of lipophilic emulsifier at first and then suddenly and discontinuously dropped when the difference in HLB of two emulsifiers is too large. These results imply 1) the HLB number of emulsifier blend markedly deviates from weight average of two emulsifiers and 2) the PIT of certain temperature range, i. e., HLB of certain range cannot be prepared by blending, provided the difference in HLB (or PIT) of two emulsifiers is too large. The emulsion droplets were smaller and the emulsion was more stable when the difference of HLB of emulsifiers to be blended is smaller in the mixture of Tween and Span type emulsifiers. There was, however, an optimum difference in HLB in ...

Structural Effects on the Properties of Nonionic Surfactants. V.

Di (2-hydroxyethyl) ether of 4, 9-dodecanediol was prepared and polyoxyethylated using basic catalyst to give the following nonionics (AD-12-4, 9 series).HO (C2H4O) m/2CH (n-C3H7) (CH2) 4CH (n-C3H7) O (C2H4O) m/2H Polyoxyethylated 1, 12-dodecanediol (AD-12-1, 12 series) and 1, 14-tetradecanediol (AD-14-1, 14 series) were also prepared.Some physicochemical properties of these new type nonionics were compared with those of 1-dodecanol-EO adducts (S-12 series) and other nonionics, in order to clarify the effects of relative position of two POE chains attached to n-alkane. Cloud points of aqueous solutions of these AD series were lower than those expected from their Davies's HLB values. Critical micelle concentrations and aqueous surface tensions of these AD series were considerably higher than those of comparable S series. Molecular areas of both AD-12 series were about two times larger than that of S-12 series. These results were discussed in terms of the characteristic configuration of these nonionics and the hydration mode of their POE chains in surface film or micellar surface. The gross effects such as foaming, wetting and anti-foaming powers of these AD series were also measured and compared with those of other types of nonionics.

Salting in of nonionic surfactants by complexation with inorganic salts

The following cations were found to salt in polyoxyethylated compounds, raising the cloud point of aqueous solutions of i-octylphenol.10 EO and that of (EO) 400 previously reduced to 45° by the addition of sodium sulfate: H +, Pb 2+, Cd 2+, Mg 2+, Ni 3+, Al 3+, Ca 2+, and Li +. Only Na +, K +, and NH 4 + salted the polyoxyethylated compounds out, lowering their cloud points. The ether linkages act as ligands, possibly polydentate, for the cations. The capacity of cations to salt in polyoxyethylated compounds runs parallel with their capacity to form complexes with simple ethers such as ethyl ether, dioxane, and cineole, and to bind water in solid hydrates. All three phenomena are widespread.

Synthesis and study of demulsifying capabilities of ethoxylated ethylenediamides of fatty acids

1. For the first time, ethoxylated ethylenediamides of individual fatty acids have been synthesized and investigated as demulsifiers of crude oil emulsions. 2. It has been established that the maximum demulsifying capability and maximum cloud point of aqueous solutions of the synthesized compounds are observed at the same values of alkyl chain length (C11–C15) in the nonionic surfactant molecule. 3. The ethoxylated ethylenediamides of acids with alkyl chain length of C11–C15 are equal in efficiency to the demulsifier most widely produced in our country, OZhK; hence, they can be recommended for development of commercial production technology.

Macromolecule hydration and the effect of solutes on the cloud point of aqueous solutions of polyvinyl methyl ether: A possible model for protein denaturation and temperature control in homeothermic animals

The effects of strong, neutral, 1:1 electrolytes; MgSO 4; urea, tetraalkylammonium salts, sucrose, and alcohols on the cloud point temperature of aqueous solutions of polyvinyl methyl ether have been examined and are interpreted in terms of (1) the two types of water structure, coulombic and hydrophobic, comprising the hydration sheath of polymer, (2) the selective exclusion of solute from the polymer's hydration sheath, and (3) the solute's stabilization or destabilization of the polymer's hydration sheath. The last two of these processes are related to the viscosity B-coefficient of the solute ions. The behavior of the polymer exhibits both similarities to and differences from proteins, and caution must be exercised in the use of the cloud point phenomenon as a model of protein denaturation. The solute effects described in this paper suggest a possible experimental test of the hypothesis that the thermal destruction of a biopolymer's hydration sheath might provide the basis of temperature control in homeothermic animals.