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This paper reports the development in aqueous solution of mixed micelles of tunable cloud point temperature through blending in various proportions of two copolymers of different chemical natures. For that purpose, a lipid-b-poly(2-isopropyl-2-oxazoline) (lipid-b-P(iPrOx)) copolymer, self-assembling into thermosensitive micelles that phase-separate above a cloud point temperature of 38 °C, was blended in various proportions with commercial C18-b-PEOx. The latter was constituted of a hydrophobic saturated C18 chain and a hydrophilic poly(ethylene oxide) (PEO) block with varying polymerization degrees (x) and does not have any thermosensitive properties on the studied temperature range for any value of x. The different blends were thoroughly characterized by light scattering and UV-visible spectroscopy, revealing that hybridization between both copolymers always occurred, independent of the PEO block length. The resulting mixed micelles present TCP values progressively increasing with the C18-b-PEOx proportion, from 38 to 61 °C. This study demonstrates the relevance of the blending approach to tune the phase separation of micellar systems by formulation rather than by more tedious synthetic efforts. Shifting TCP through this approach extends the range of temperature where lipid-b-P(iPrOx) can find an application.

The present review is devoted to a class of organic analytical reagents 6,7- and 7,8-dihydroxybenzopyrylium derivatives: their synthetic pathways, physicochemical properties, state in solutions, and analytical applications are described. Anion nature influence on spectral characteristics and some physico-chemical properties of 6,7-dihydroxybenzopyrylium derivatives was noted. Pathways of acid-base transformations in aqueous solutions of 6,7-dihydroxybenzopyrylium derivatives were described. It has been shown that derivatives of 6,7- and 7,8-dihydroxybenzopyrylium are capable for complexation with a number of p-, d-, and f-elements (Cu (II), Ga (III), In (III), Tl (III), Ge (IV), La (III), titanium subgroup, Bi (III), Mo (VI), W(VI) and others). Information on their composition, structure and analytical characteristics is summarized. It is noted that with the 6,7-dihydroxybenzopyrylium derivatives the simple and highly sensitive methods for the direct spectrophotometric and extraction-photometric determination of Ga(III), In(III), Tl(III), Ti(IV), Zr(IV), Hf(IV), Mo(VI), Ge(IV), Bi(III), Cu(II) have been developed. It is noted that 6,7-dihydroxybenzopyrilium derivatives complexes with Mo(VI) and Cu(II) are effectively extracted by Triton X‑100 micellar phase, which forms the basis for highly sensitive combined spectrophotometric and atomic absorption methods for their determination. The simplicity of targeted synthesis of 7,8- and 6,7-dihydroxybenzopyrylium derivatives opens the way to their use in the development of combined cloud point extraction and liquid-liquid microextraction with spectrophotometric or atomic absorption detection methods for the determination of a number of p- and d-elements.

A green and simple method, dynamic microwave-assisted micelle extraction coupled with cloud point preconcentration, was developed for the determination of triazine herbicides in soil samples. The method has the advantages of those two extraction procedures, which could eliminate the interferences from complex soil samples greatly. Non-ionic surfactant Triton X-114 aqueous solution used as extraction solvent was continuously pumped into soil samples. The resulting extract was heated and centrifuged in the presence of NaCl. After centrifugation, the analytes were enriched into the surfactant-rich phase. No filtration or cleaning steps were required. Several key parameters were investigated. The Box–Behnken design was applied to optimize the experimental factors involved in the dynamic microwave-assisted micelle extraction. Good linearity was observed in the range of 1.00–250.00 μg kg−1. The limits of detection were ranged between 0.26 and 1.71 μg kg−1. The recoveries of analytes ranged from 80.3 to 98.3% with the relative standard deviations ranging from 1.1 to 6.6%.

The increasing usage of zinc oxide nanoparticles (ZnONPs) inevitably leads to their release into the environment. To understand their fate and toxicity in water systems, a reliable method for the quantitative analysis of ZnONPs in environmental waters is urgently needed to be established. In this study, a quantitative analytical method of ZnONPs in environmental waters was developed by cloud point extraction (CPE) combined inductively coupled plasma mass spectrometry (ICP-MS). To obtain high recoveries of ZnONPs, the CPE parameters including pH, surfactant concentration, salt concentration, bath temperature, and time were optimized. The results demonstrated that the addition of β-mercaptoethylamine could significantly reduce the interference of Zn2+ on the extraction of ZnONPs, while the CPE approach was not affected significantly by the typical environmental inorganic ion and ENMs (such as Au, TiO2, and Al2O3). The extraction method of ZnONPs with different diameters was also assessed, and satisfactory extraction efficiency was obtained. The results of ZnONP concentration in collected environmental water were in the range of 0.2 ± 0.009 - 8.2 ± 1.8 μg/L. And the recoveries of ZnONPs in different environmental waters were 62.2 ± 2.0 - 88.1 ± 9.6 % at low concentration spiked levels (12.57-54.68 μg/L), demonstrating that it is efficient to extract trace ZnONPs from real environmental waters. This established method offered a reliable method for the quantitative determination of ZnONPs in environmental waters, which could further promote the study of the environmental behavior, fate, and toxicity of ZnONPs in an aqueous environment.

The gelation behavior of methylcellulose (MC) was studied by the dynamic mechanical analysis and UV-spectroscopy. To investigate the chain elastic response the dynamic strain experiment is performed at various temperatures, where the decrease in the peak heights with an increase in temperature reveals the increase in rigidity of the sol-gel network. The continuous rotation of functional groups induces turbidity in MC, therefore the association of –OCH3 groups or appearance of cloud point occurs earlier to the gel point. The area under the various curves also signifies the bridging percolated network of the MC aqueous system. Further, the mechanism of gelation is described as an equilibrium among the trans- and gauche-conformations. Computationally, various angles in the cyclic monomeric units of MC and the torsional angles in adjacent monomeric units are reconnoitered to describe the stability of the helical structure of MC.

Aims: The main aim of the study was to examine the feasibility and benefits of adsorption onto multi-walled carbon nanotubes (MWCNTs) coupled with cloud point extraction (CPE) for the removal of Rhodamine B (RB) from aqueous solutions. Background: MWCNTs offer the particular features of the ideal adsorbents for the organic dyes such as hollow tubular structure and specific surface area. Nevertheless, they suffer from the drawbacks of low dispersion in the aqueous solutions and separation inconvenience from the media. Cloud point extraction, combined with the adsorption onto MWCNTs can be a promising method to overcome the problems. Objective: In the study, adsorption onto MWCNTs coupled with CPE was applied for RB removal from aqueous solutions. The process was optimized by the response surface modeling method. Moreover, the applicability of the proposed method in the real sample analyses was investigated. Methods: MWCNTs were used as adsorbent and Triton X-100 (TX-100) as the nonionic surfactant for CPE process. The experiments were carried out based on a Box-Behnken design (BBD) with the input variables of MWCNTs dosage (0.6-1.2 mg), solution pH (3–9), clouding time (20-40 min) and TX-100 concentration (10-20 v/v%) using 5 mg L-1 RB solutions. Result: Regression analyses resulted in a statistically significant quadratic model (R2=0.9718, F=24.96, p#60;0.0001) by which the optimum levels of the variables were predicted as: MWCNTs dosage of 0.7 mg, pH=3, clouding time of 39.9 minutes and TX-100 concentration of 19.91% (v/v). The predicted conditions were experimentally validated by achieving an RB removal of 94.24%. Conclusion: Based on the results, the combination of the environmentally friendly technique of CPE with adsorption onto MWCNTs allows the efficient removal of RB from water samples and the method can be effectively optimized by the response surface modeling.

Poly(N-isopropylacrylamide) (PNIPAM) is a representative thermoresponsive polymer, and its aqueous solution becomes phase-separated at a temperature higher than the cloud point (Tcₚ) at ∼304 K, which plays an important role in various biomedical applications. Thus, to further promote the use of PNIPAM as a functional material, it is necessary to gain a better understanding of its phase behavior especially at a temperature just below Tcₚ. To this end, we examined the local rheological properties of atactic PNIPAM solutions with a concentration of 10 wt % by a particle tracking technique, in which the thermal motion of probe particles in the solution was tracked, in conjunction with Fourier-transform infrared spectroscopy, small-angle X-ray scattering measurements, fluorescence spectroscopy, and confocal laser scanning microscopy. At temperatures far below Tcₚ, the solution exhibited one-phase homogeneous characteristics. After the PNIPAM aqueous solution was left undisturbed at a temperature just below Tcₚ (302 K), it formed a physical gel. Changing the size of probe particles for the tracking measurements, we found that the resultant gel was spatially heterogeneous in terms of its rheological properties at a length scale of approximately 50–100 nm. The gelation of the solution promoted by the formation of hydrophobic pearls in PNIPAM chains led to the formation of network junctions with heterogeneity. The knowledge obtained here should be useful for understanding and controlling the phase behavior of the PNIPAM solution, thereby leading to the further development of thermoresponsive functional materials.

The extraction properties of original mixed micellar systems, Triton X-114/N-alkylsalicylideneimine type amphiphilic Schiff bases, have been investigated for removal of nickel(II) from aqueous solutions. The acid-base behavior of chelating Schiff bases in aqueous micellar solution was first studied, and their acidity constants were determined. The phase diagram of Triton X-114/water micellar system was then established, The cloud point extraction of nickel(II) by mixed micelles Triton X-114/amphiphilic Schiff base ligand was studied in a concentrated chloride medium, as function of pH, extractant and surfactant concentrations, temperature and time. The stoichiometry of the extracted Ni(II)-complexes was finally determined.

Carnosic acid (CA) is a hydrophobic secondary metabolite and the main antioxidant of rosemary. Extractions of CA from whole leaves of rosemary have been performed with aqueous solutions of twelve s...

The thermoresponsive behavior of a poly(2-oxazoline)-based molecular brush is investigated in aqueous solution. The molecular brush under study, PiPOx100-g-PEtOx17, has a poly(2-isopropenyl-2-oxazoline) (PiPOx) backbone grafted with thermoresponsive poly(2-ethyl-2-oxazoline) (PEtOx) side chains. Since the backbone degree of polymerization is only a factor of ~ 6 higher than the ones of the side chains, it features an architecture between a star-like polymer and a comb-like polymer. Its aqueous solution exhibits lower critical solution temperature (LCST) behavior with a cloud point temperature Tcp = 40.5 °C at 30 g L−1. The temperature-dependent structural evolution is disclosed using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). An increase of the molecular brush size is found upon heating from room temperature to Tcp, which is attributed to the extension of the backbone resulting from the dehydration and collapse of the side chains. Above Tcp, the size decreases again, which indicates the collapse of the whole molecular brush. Large aggregates are found to be present in the solution in the temperature range 25–50 °C. These become more compact, as the temperature is increased across Tcp.

The novel approach of cloud point extraction in the presence of multi-walled carbon nanotubes (CPE/MWCNTs) is presented for removal of Direct Green 26 (DG26) from aqueous solutions. The experiments were conducted based on the Box-Behnken experimental design and the removal process was optimized by the response surface modeling and desirability function (DF) approach. Effects of the experimental variables (MWCNTs amount, solution pH, clouding time and volume of Triton X-100 solution) on the process efficiency were modeled using a quadratic equation with the coefficient of determination (R2) value of 0.9944 and Fisher ratio of 177.07. Using the DF approach, optimum levels of the variables determined as MWCNTs amount of 0.7 mg, pH 3, clouding time of 40 min and Triton X-100 solution volume of 993 µL. Experimental checking of the conditions resulted in the dye removal efficiency of 95.86%. Results of the study proved the applicability of the proposed method for DG26 removal from real water samples.

Toxicity and transport of metal-based nanoparticles (M-NPs) in environmental waters strongly depend on their speciation. A detailed understanding of the composition and speciation of M-NPs is necessary in order to move this field forward. Unfortunately, there is a shortage of analytical methods for metal-sulfide nanoparticles (MS-NPs) in the environment. In this work, a cloud point extraction (CPE) method combined with liquid chromatography hyphenated to inductively coupled plasma mass spectrometry (LC-ICPMS) is developed for sensitive determination of Ag2S- and ZnS-NPs. Under the condition of 0.15% (w/v) of Triton X-114 (TX-114), pH 5, 20 mM NaNO3, incubation temperature of 45 °C, and time of 15 min, MS-NPs and non-MS-NPs were extracted into the surfactant-rich phase. With the sequent addition of 10 mM bis(p-sulfonatophenyl)phenylphosphane dehydrate dipotassium (BSPP) aqueous solution (100 μL) into the CPE-obtained extract, the non-MS-NPs were selectively dissociated into their ionic counterparts while maintaining the original size and shape of Ag2S- and ZnS-NPs. Interestingly, the micelle-mediated behavior suddenly disappeared with the addition of BSPP. Thus, the extract can be injected to LC-ICPMS for speciation analysis of trace Ag2S- and ZnS-NPs. This method exhibited excellent reproducibility (relative standard deviations < 4.9%), high sensitivity with the respective detection limits of 8 ng/L for Ag2S-NPs and 15 ng/L for ZnS-NPs, enabling recoveries of 81.3-96.6% for Ag2S-NPs and 83.9-93.5% for ZnS-NPs when they were spiked into three environmental water samples. Due to its potential applicability to low concentrations of Ag2S- and ZnS-NPs, this method is particularly convenient for monitoring the transformations of AgNPs and ZnO-NPs in the environment.

A dynamic thermo-responsive drug delivery concept using poly(2-oxazoline) copolymers conjugated with a hydrophobic drug is presented. The novel strategy entails the synthesis of copolymers comprising 2-n-propyl-2-oxazoline and 2-methoxycarbonylpropyl-2-oxazoline to which the drug, benazepril is conjugated via an ester linkage. The polymer without drug is non-toxic and has a cloud point temperature in aqueous conditions around 50 °C meaning that it is soluble at body temperature. Yet, when conjugated with the drug, the cloud point temperature decreases to in between 0 and 30 °C, depending on the quantity of drug coupled to the polymer. Conversely, as the drug is cleaved via ester hydrolysis, the cloud point temperature shifts to higher temperature and the polymer becomes soluble. This shift in cloud point temperature from above to below body temperature upon modification of the polymer with the drug benazepril is hypothesized to make it suitable as an injectable soluble polymer-drug conjugate that forms an insoluble depot to slowly release the pristine drug followed by redissolution of the drug-free polymer.

The cloud point extraction experiments of La(III) ions using the C13E10 as non-ionic surfactant were carried out. The experimental optimization was realized by the classical method when optimizing one experimental factor at the time. The results showed that the La(III) ions were extracted at 61.77% and stripped from the loaded coacervate phase at 90.26% in one-stage with the nitric acid solution of 10−1 M. The most influent experimental factors such as: initial concentration of feed phase (A), C13E10 concentration (B), quantity of sodium chloride salt (C) and pH of aqueous feed solution (D) were studied by the Taguchi’s DOE methodology using an orthogonal array L9 (3^4). Statistical study based on the ANOM and ANOVA analysis showed that the factor D constituted a noise and the levels optimum combination for the maximum extraction yield of La(III) was at: C0 = 150 ppm and [C13E10] = 15% w/w without the add salt. These results were refined by using the Design-Expert 7 software where the predicted extraction yield of La(III) was in good agreement with that obtained experimentally (62.88% against of 61.77%), in which the standard deviation was of 1.81%.

International audience; Using CO$_2$ as a resource in the production of materials is a viable alternative to conventional, petroleum-based raw materials and therefore offers great potential for more sustainable chemistry. This study presents a detailed structural characterization of aggregates of nonionic dodecyl surfactants with different amounts of CO$_2$ substituting ethylene oxide (EO) in the head group. The micellar structure was characterized as a function of concentration and temperature by dynamic and static light scattering and, in further detail, by small-angle neutron scattering (SANS). The influence of the CO$_2$ unit in the hydrophilic EO group is systematically compared to the incorporation of propylene oxide (PO) and propiolactone (PL). The surfactants with carbonate groups in their head groups form ellipsoidal micelles in an aqueous solution similar to conventional nonionic surfactants, becoming bigger with increasing CO$_2$ content. In contrast, the incorporation of PO units hardly alters the behavior, while the incorporation of a PL unit has an effect comparable to the CO$_2$ unit. The analysis of the SANS data shows decreasing hydration with increasing CO$_2$ and PL content. By increasing the temperature, a typical sphere–rod transition is observed, where CO$_2$ surfactants show a much higher elongation with increasing temperature, which is correlated with the reduced cloud point and a lower extent of head group hydration. Our findings demonstrate that CO$_2$-containing surface-active compounds are an interesting, potentially “greener” alternative to conventional nonionic surfactants.

For the selective extraction of silver, a cloud point extraction (CPE) procedure was developed. After synthesizing the solvation species through the reaction of silver ions with 2, 4-dimethyl pentane-3-one (2,4 DMP), the salting-out agent (0.4 mol L-1 NaNO3) was added at 35 °C and, after 10 min, Triton X-114 was used to separate silver ions from aqueous solution. The type and quantity of salting-out agent, silver ion, temperature, heating time, and surfactant volume were all examined as important factors determining the CPE. The analytical curve in the 0.1-100 μg L-1 Ag range was straight at optimal conditions. The detection limit (LOD), quantification limit (LOQ), and enrichment factor (E) were 0.05 µg L-1, 0.15 µg L-1, and 200, respectively. The relative standard deviation (RSD) was estimated as 0.2-3.9% (n = 5) in relation to 1, 40, and 80 μg L-1 Ag. Flame atomic absorption spectrometry and spectrophotometry exploiting dithizone were used to assess the CPE accuracy. The proposed approach was then applied to river water, rain water and sand samples.

Cloud point driven interaction and relaxation dynamics of aqueous solutions of amphiphilic thermoresponsive copolymers were explored through picosecond resolved and steady state fluorescence measurements employing hydrophilic (coumarin 343, C343) and hydrophobic (coumarin 153, C153) solute probes of comparable sizes. These thermoresponsive random copolymers, with tunable cloud point temperatures (

Aqueous biphasic systems containing non-ionic ethoxylated surfactants are perspective as media for some biochemical reactions. A comprehensive study of phase and aggregation behavior of these micellar systems, as well as consideration of the effects of biocomponents, their nature and concentration, pH and temperature are evident. In this work, the influence of salt medium (phosphate buffer), pH and temperature, as well as the presence of different bioorganic additives on cloud point and structural-thermodynamic properties (CMC and aggregation number) were studied for micellar solutions of non-ionic surfactants Triton X-114 and Tergitol NP-7 in water and buffers with pH 6.8, 4.3, 2.7. As additives were used the components of a biocatalytic hydrolysis reaction of penicillin G, namely penicillin G potassium salt, phenylacetic acid, and 6-aminopenicillanic acid. The different effects of the biocomponents on the cloud point and CMC value of Triton X-114 in the buffer with pH 4.3 are discussed. In addition, it was shown that the CMC value and the aggregation number of Triton X-114 decrease in buffer solutions (salting-out effect) and the CMC value increase at growing the temperature to 37°C (what is typical for ethoxylated non-ionic surfactants). The addition of phenylacetic acid (10 mM) leads to a reduction in the aggregation number of Triton X-114 at pH 4.3; other bio-additives have practically no effect. Thus, the studied additives have different effects on the structure and phase behavior of investigated micellar solutions, and this is an important aspect for choosing an extraction system to carry out a bioreaction.

We measured the self-diffusion coefficients of mixed micelles formed in binary mixtures of oxyethylated isononylphenols (neonols) AF9-2,3,4,6,8,9,10,12 by NMR diffusometry in aqueous 1 wt% solution...

In this study, cloud point extraction‒scanometry as a new, simple and inexpensive method was developed for the separation, preconcentration and determination of trace amounts of brilliant green (BG) and basic fuchsin (BF) in mixture. The method is based on the extraction of analytes simultaneously from aqueous solution using a non-ionic surfactant Triton X-114 as a cloud point extractor. After phase separation, the surfactant-rich phase was diluted with ethanol, digital image of the solution taken with a flatbed scanner and RGB parameters of the enriched analytes were calculated by special software written in visual basic (VB 6). The influence of analytical parameters including pH of system, the concentration of the surfactant, equilibration temperature and time were optimized. The method was linear in the concentration ranges of 0.025‒1.00 and 0.05‒2.50 mg/L with limits of detection of 0.008 and 0.019 mg/L for BG and BF, respectively. The preconcentration factors were 29 for BG and 28 for BF. The enrichment factors were found to be 34 and 16, precision (RSD, %) of the method, 1.9 and 1.3% for BG and BF, respectively. The effects of interfering ions and dyes were investigated. Finally, the proposed method was applied for the determination of BG and BF in real water samples with satisfactory results.

Recently, cloud point extraction (CPE) coupled with back extraction (BE) has been suggested as a promising alternative to liquid-liquid extraction. In CPE, non-ionic surfactants in aqueous solutions form micelles and the solution becomes turbid when heated to the cloud point temperature. Microwave- or ultrasonic-assisted BE can be performed after CPE and before injection of the sample for instrumental analysis by ultraviolet-visible spectroscopy, high-performance liquid chromatography, gas chromatography, gas chromatography-mass spectrometry, or liquid chromatography-mass spectrometry. This article reviews selected published scientific research on the application of CPE-BE to the determination of alkaloids, drugs and organophosphorus compounds from several complex matrices. This method could be scaled-up for use in forensic science.

Most polymers used in commercial kinetic hydrate inhibitor (KHI) formulations show thermoresponsive behavior in aqueous solution. This means that they exhibit a cloud point (or lower critical solut...

The assembly of oppositely charged block copolymers, containing small thermoresponsive moieties, was investigated as a function of salt concentration and temperature. Aqueous solutions of poly-[N-isopropylacrylamide]-b-poly[dimethylaminoethyl methacrylate] (NIPAM44-b-DMAEMA216) and PNIPAM-b-poly[acrylic acid]-b-PNIPAM (NIPAM35-b-AA200-b-NIPAM35) were mixed in equal charge stoichiometry, and analysed by light scattering (LS), NMR spectroscopy and small angle X-ray scattering (SAXS). At room temperature, two different micelle morphologies were found at different salt concentrations. At NaCl concentrations below 0.75 M, complex coacervate core micelles (C3M) with a PNIPAM corona were formed as a result of interpolyelectrolyte complexation. At NaCl concentrations exceeding 0.75 M, the C3M micelles inverted into PNIPAM cored micelles (PCM), containing a water soluble polyelectrolyte corona. This behavior is ascribed to the salt concentration dependence of both the lower critical solution temperature (LCST) of PNIPAM, and the complex coacervation. Above 0.75 M NaCl, the PNIPAM blocks are insoluble in water at room temperature, while complexation between the polyelectrolytes is prevented because of charge screening by the salt. Upon increasing the temperature, both types of micelles display a cloud point temperature (Tcp), despite the small thermoresponsive blocks, and aggregate into hydrogels. These hydrogels consist of a complexed polyelectrolyte matrix with microphase separated PNIPAM domains. Controlling the morphology and aggregation of temperature sensitive polyelectrolytes can be an important tool for drug delivery systems, or the application and hardening of underwater glues., The assembly of oppositely charged block copolymers, containing small thermoresponsive moieties, was investigated as a function of salt concentration and temperature.

Here we report, a comparative study on the micellization and phase behavior of two commercially available ethylene oxide – propylene oxide (EO-PO) octablock copolymers, Tetronics® 1304 and 1307 (hereafter written as T1304 and T1307), in the presence of 2,2,2‑trifluoroethanol (TFE) and ethanol (EtOH) using cloud point (CP), dynamic light scattering (DLS), high sensitivity differential scanning calorimetry (HSDSC), relative viscosity and Langmuir film balance. These copolymers fabricated with almost the same PO block length vary in their EO chain lengths and hence display different characteristics. T1304 shows a more hydrophobic character and forms micelles at ambient temperature while T1307, due to longer EO chain length, exhibits high hydrophilicity and faces difficulty in forming micelles which results into high polydispersity in the aqueous system. In the presence of co-solvents TFE and EtOH, however a more interesting behavior is noted. T1304, as evident from DLS and viscosity measurements, displays micellar growth in the presence of TFE, while the presence of EtOH induces micellar breakdown. Though, in case of T1307, presence of TFE improves micellization and a single micellar peak becomes evident in the DLS stacks, no micellar growth can be noticed both through DLS and relative viscosity, which is possibly due to its highly hydrophilic character. Likewise, presence of TFE depresses the CMT in both the copolymers while EtOH increases it. A similar trend is also justified by π-A isotherms form Langmuir monolayers.

Measurements of clouding phenomena in Triton X-100 (TX-100) were carried out in the aqueous system and the presence of the antibiotic drug levofloxacin hemihydrate (LFH)/(LFH + inorganic salts/alcohols) and were explained thoroughly. In the aqueous system, the observed values of cloud point (CP) of TX-100 increased continuously with the increasing concentration of TX-100. In the occurrence of LFH, the magnitudes of cloud point of a certain concentration of TX-100 were found to increase first, and after that, the CP value declined with increasing concentration of the drug. The magnitudes of CP for the LFH + TX-100 mixed system were found to be dwindled through the enrichment of salt concentration in the presence/absence of a drug (LFH). The CP values in the presence of salts follow the order K2SO4 < KNO3 < K3PO4. On the other hand, in the case of alcohol solvent, the CP values decreased from lower alcohol to higher alcohol and increased through the enrichment of alcohol concentration in the presence and ab...

The understanding of molecular structure and thermoresponsive property relationships and development of water-soluble thermoresponsive polymers with tunable cloud point temperatures (Tcps) are crucial toward versatile practical uses. Herein, OEGylated polypeptides bearing Y-shaped pendants, namely poly(γ-4-(propoxycarbonyl)benzyl-L-glutamate)-oligo(ethylene glycol) conjugates (8-OEGx, x = 2, 3) were synthesized by the combination of ring-opening polymerization of γ-4-(allyloxycarbonyl)benzyl-L-glutamic acid based N-carboxyanhydride (4) and subsequent side-chain modifications, including bromination of poly(γ-4-(allyloxycarbonyl)benzyl-L-glutamate) (5), nucleophilic substitution of 5 in the presence of NaN3, and subsequent copper-mediated 1,3-dipolar cycloaddition. Both 1H NMR and FTIR analysis confirmed the molecular structures of the intermediates and 8-OEGx. In aqueous solutions, 8-OEGx samples showed reversible lower critical solution temperature (LCST)-type phase transitions in broad polymer concentration range (0–30 mg·mL−1). Variable-temperature UV–vis spectroscopy results revealed that the LCST-type Tcp of 8-OEG2 at high polymer concentrations (e.g., ≥10 mg∙mL−1) was in the range of 37.5–42.5 °C. 8-OEG2 showed a remarkable increase of hydrophilicity than PBLG-OEG4 with the same amount of OEG units as well as linear shaped pendants. The Tcp of OEGylated polypeptides increased by addition of NaI, yet it decreased upon addition of NaCl, NaBr, or KCl, which obeys the Hofmeister effect.

OEGylated homopolypeptide (i.e., P(Azo-S-OEG7)) bearing azobenzene, thioether spacers, and oligo(ethylene glycol) OEG tails were prepared via a copper-mediated 1,3-dipolar cycloaddition. P(Azo-S-OEG7) showed an upper critical solution temperature (UCST)-type thermo-, light-, and oxidation-responsive in ethanol/water solvent mixtures. The UCST-type cloud point temperature (Tcp) decreased after UV irradiation and it increased after visible light irradiation due to the trans-cis isomerization of azobenzene moieties. P(Azo-S-OEG7) can be readily oxidized in the presence of H2O2, yielding P(Azo-SOX-OEG7) with sulfone or sulfoxide spacers. P(Azo-SOX-OEG7) showed an increase of UCST-type Tcp after UV irradiation and the Tcp decreased after visible light irradiation, which is an opposite trend to the UCST-type phase behavior of P(Azo-S-OEG7) as well as previous report. P(Azo-S-OEG7) showed poor water-solubility, yet it underwent H2O2 induced solution phase transition yielding P(Azo-SOX-OEG7) with lower critical solution temperature (LCST)-type phase behavior in water. The P(Azo-SOX-OEG7) aqueous solutions showed a decrease of LCST-type Tcp after UV irradiation and consequently Tcp decreased after visible light irradiation.

The use of thermosensitive polymers exhibiting an upper critical solution temperature (UCST) for sensing and detecting the presence of CO2 in aqueous solution was demonstrated. By synthesizing random copolymers of acrylamide (AAm), acrylonitrile (AN) and N,N-diethylaminoethyl methacrylate (DEAEMA), which have different relative contents of AAm and AN but a similar and small amount of CO2-responsive DEAEMA (below 3%), two means for monitoring the concentration of CO2 through the transparency change of a polymer sensor solution were investigated. On the one hand, using a single P(AAm-co-AN-co-DEAEMA) copolymer whose phase transition-induced transmittance change upon cooling is completed within a narrow temperature range and whose cloud point (CP) is sensitively decreased upon increasing the amount of CO2, the polymer solution at a given temperature (25 °C) allows a threshold concentration of CO2 to be detected by showing an abrupt change in transmittance. On the other hand, by mixing two copolymers with largely different CPs (over 30 K), the sharp UCST-type phase transition is suppressed; instead the change in the solution transmittance upon cooling proceeds slowly and gradually over a wide temperature region (>35 K). The mixed polymer solution can be used to monitor the increase in the amount of CO2 through gradual and mostly linear changes in transmittance. Both abrupt and gradual transparency changes can be observed by the naked eye.

A novel type of multi-stimuli responsive dendrimer with thermo-, pH-, and CO2-responsiveness was developed through facile modification of polyamidoamine dendrimers (PAMAM) with various N-dialkylaminoethyl carbamate moieties. A series of modified PAMAM dendrimers with a well controlled structure were obtained and characterized by 1H NMR. The aqueous solutions of these dendrimers showed a lower critical solution temperature (LCST)-type thermoresponse, and their cloud point temperature (Tcp) was determined by turbidity measurements. Tcp was tunable from 8 to 70 °C, depending on the hydrophobicity and substitution number of the terminal N-dialkylaminoethyl groups, PAMAM generation, pH values, and salt concentrations. Additionally, the solubility of the resultant dendrimers could be reversibly modulated by alternately bubbling CO2 and argon. Our study offers a simple but effective approach to making new multi-stimuli responsive dendrimers for potential smart material applications.

Cloud point extraction (CPE) is a simple, fast, inexpensive and environmental friendly methodology for preconcentration in extraction of trace organic pollutants from aqueous solutions. CPE has been developed and modified by various researcher to improve the method. This paper is review and compilation of the whole development and modification of CPE from the research group of Noorashikin Md Saleh from year 2013 to 2018 that focus on extraction of organic pollutant which is parabens (methylparaben, ethylparaben, propylparaben and benzylparaben). Modification done by using different surfactants (Sylgard 309 and DC193C) and adding modifier (β-cyclodextrin) into the CPE method and to compare the effectiveness of the modification. The preconcentration and extraction is analysed using analytical instruments such as ultra-violet spectrometry (UV-Vis) or high performance liquid chromatography coupled with ultra-violet spectrometry (HPLC-UV). Each developed method will have parameters optimization such as effect of salt concentration, surfactant and modifier concentration, temperature, pH and extraction time. Each successful development and modification of methodology is validated on various kind of samples such as water samples, beverages and cosmetic products. The limit of detection for parabens extraction using CPE with Sylgard 309, DC193C and DC193C with β - cyclodextrin were 0.01 – 0.02 μg/L, 0.17–0.20 μg/L, and 0.017–0.027 μg/L respectively while the percentage recovery for water samples using CPE with Sylgard 309, DC193C and DC193C with β-cyclodextrin were 80.5–95.2%, 71.2–97.7% and 90.3–98.9% respectively. In addition, the percentage recovery for beverages using CPE with Sylgard 309 and DC193C were 76.4–117.4% and 80.9–106.4% respectively while the percentage recovery for cosmetics using CPE and Sylgard 309 were 69.6–112.8%. Throughout the research, it shows that CPE have potential to work with different surfactants in preconcentration for extraction of parabens from aqueous samples.

A new multi-stimuli responsive tryptophan-based styryl homopolymer exhibiting dual upper critical solution temperature (UCST)- and lower critical solution temperature (LCST)-type thermosensitivities under different conditions is presented. The monomer 4-vinylbenzyl N-[(tert-butoxy)carbonyl]-L-tryptophan (Boc-TrpVBz) is prepared by a simple substitution reaction followed by its subsequent RAFT polymerization to produce the poly(Boc-TrpVBz) homopolymer. Poly(Boc-TrpVBz) is not soluble in water, but is soluble in different organic solvents (such as DMSO, DMF and MeOH). An interesting upper critical solution temperature (UCST)-type turbid-to-transparent phase transition is detected for poly(Boc-TrpVBz) in mixed solvents containing any of these three solvents and a minimum percentage of water. The UCST-type cloud point is found to increase upon increasing the percentage of added water and the molecular weight of poly(Boc-TrpVBz). Furthermore, poly(Boc-TrpVBz) is soluble in water at above pH 7.5 and exhibits a lower critical solution temperature (LCST)-type transparent-to-turbid transition upon addition of tetrabutylammonium halide salts with a large organic cation. The LCST-type cloud point is variable with respect to the salt concentration and the nature of the halide ion. The deprotection of the Boc moiety of poly(Boc-TrpVBz) produces zwitterionic poly(TrpVBz) containing –NH2 and –COOH groups, which exhibits dual pH- and thermo-responsiveness in aqueous solution below pH 2. In the cases of UCST- and LCST-type transitions, the turbidity is caused by the formation of spherical polymer aggregates as observed via TEM and FESEM.

This paper describes the experimental elucidation for the impact of polypeptide sequence on the solution structure and the thermo-responsivity, having considered the corresponding theoretical prediction using a binary pattern of hydrophobic and hydrophilic units. We prepare diblock, random, and alternating copolymers consisting of a stoichiometric amount of valine as a hydrophobic unit and glycine as a hydrophilic unit. Through the thermo-responsivity measurements of aqueous polymer solutions, it is found that the UV spectra of diblock copolypeptide exhibit a cloud point upon heating, which indicate that the polymer adopts a random coil structure at low temperature. On the other hand, the alternating peptide shows an upper critical solution temperature (UCST) behavior indicating a globule-to-coil transition upon heating. The opposite behavior of alternating peptide to that of diblock copolypeptide is found to be dependent on not the chirality of repeating units but the alternating binary pattern of hydrophobic and hydrophilic units. The random copolypeptide exhibits not only coil-to-globule transition at low temperature but also globule-to-coil transition at high temperature owing to the presence of both segregated and alternating polymer sequences in the polymer. The thermo-responsive structures of the polymers in an aqueous media are also discussed by determining the thermodynamic parameters for the transitions.

New simple sensitive spectrophotometric methods are developed for the estimation of Sulfadoxine (SFD) in pure and pharmaceutical formulations. The first method includes a conversion primary amine to azo-dye by reacting sulfadoxine with sodium nitrite and hydrochloric acid followed by coupling with4-methoxyphenol in alkaline medium to obtain a stable reddish-orange colored dye at λmax495nm. Concentration ranges 0.25-60 μg / mL, obeyed Beer's law, correlation coefficient was 0.9996, molar absorptivity was 0.589×104L.mol-1.cm-1 and the detection limit was 0.157μg/mL. The second method was cloud point extraction (CPE) for estimating trace amount in an aqueous solution that produced from diazotization and measuring with a UV-visible spectrophotometer as are reddish-purple colored product at λmax500 nm. The concentration range obeyed the Beer's law was 0.25-6μg / mL, correlation coefficient was 0.9998, molar absorptivity was 0.877×105L.mol-1.cm-1, detection limit was 0.023μg/mL, pre-concentration factor was 25 and Distribution coefficient(D) was 320.88. The last method was flow injection analysis it’s simple for estimation the sulfadoxine. The concentration range was1-150μg / mL, obeyed Beer's law,the correlation coefficient was 0.9997, molar absorptivity was 0.273×104L.mol-1.cm-1 and the detection limit was 0.375μg/mL. The offered methods were successful, useful for estimating sulfadoxine in traditional medications

The aqueous solubility of anionic surfactants is generally limited by their Krafft point. However, the insertion of non-ionic spacers such as ethoxy or propoxy groups between the alkyl chain and the anionic head is known to improve the water solubility of these surfactants in pure water or in the presence of electrolytes. In this work, the amphiphilicity of a series of ethoxylated or propoxylated sulfate surfactants is assessed by the PIT-slope method. Then, the phase behavior of these surfactants in concentrated aqueous solutions of NaCl or CaCl2 is investigated and compared with that of the typical nonionic (C12EO7) and ionic (SDS) surfactants. Surprisingly, sodium dodecyl sulfate presents a cloud point at high salinities and temperatures. Adding ethoxy or propoxy groups greatly enhances the resistance to electrolytes due to the “disordered” structure of non-ionic spacers that hinders crystallization, leading to Krafft point under 0 °C. Increasing the number of hydrophilic ethoxy groups increases the salt tolerance in contrast with the decrease observed with the slightly hydrophobic propoxy groups. Finally, the salt effect of CaCl2 and Ca(NO3)2. are compared pointing out the salting-out effect of Cl− and showing a weak salting-in effect of Ca2+ on nonionics and its strong interaction with sulfate anionic function.

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.

Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) samples were synthesized via aqueous atom transfer radical polymerization with DPn of 35, 151, 390, and 546 and dispersity of 1.13, 1.17, 1.20, and 1.18, respectively. All samples were exposed to temperature and pH variations at different concentration of polymer and salt (NaCl). Results indicated that cloud point (Tcl) can be controlled by changing DPn, polymer concentration, and ionic strength of solution. According to results, Tcl of the PDMAEMA chains shifted to lower temperatures with increasing solution pH at all molecular weight ranges due to deprotonation of tertiary amine groups in polymer structure. However, higher molecular weight polymers were more sensitive to pH variation especially in alkaline media. Also, higher polymer concentration acted as driving force to decrease cloud point of samples and formation of aggregates that was more predominant for higher molecular weights at alkaline media. Tcl of PDMAEMA chains decreased with increasing ionic strength even at low pH values for low molecular weight polymers.

The present study deals with the self-assembly of a pure graft copolymer: Soluplus® and a non-ionic surfactant: Solutol® HS15 and focuses on their clouding behaviour [expressed as cloud point (CP)] in the presence of different additives viz. inorganic salts (NaF, NaCl, NaBr, NaI, NaNO3, KCl, KBr, KI), bile salts (sodium cholate-NaC, sodium taurocholate-NaTC, sodium deoxycholate-NaDC), denaturants (urea, methylurea, dimethylurea), amino acids (alanine, glycine, lysine, valine, cysteine hydrochloride), sugars (glucose, fructose, mannitol, sucrose, maltose, lactose), cationic surfactants (cetyltrimethylammonium bromide-CTAB, tetradecyltrimethylammonium bromide-TTAB, dodecyltrimethylammonium bromide-DTAB) and alcohols (methanol, ethanol, propanol, 1-butanol, ethanediol, 1,3-propanediol, 1,4-butanediol). The aqueous solutions of these amphiphiles show a complex phase behaviour and have revealed the occurrences of spherical micelles using dynamic light scattering (DLS) and small-angle neutron scattering (SANS) techniques. Herein, we report the variation of amphiphilic CP in the presence of different kinds of additives that show the influence of the water structure and its hydrophobicity, making this study important for pharmaceutical/ biomedical applications.

Micellar phase control of thermoresponsive polymeric micelles (PAA-co-PAN) via upper critical solution temperature (UCST) in aqueous environment was explored using DPD simulations. Performing a thermal scan we show that above its UCST a stable micellar system is generated. When the temperature decreases below the UCST (304 K), the colloidal system becomes thermodynamically unstable generating hydrophobic particles with PAN-core and PAA-shell. A notable effect is the generation of a cloud point and this polymeric multiphase behaviour is used to show the removal of methylene-blue dye from a solution. The stages of the removal process via cloud point are shown in detail.

Herein, the aggregation, phase separation and binding behavior of sodium alginate (SA) and surfactants (anionic (SDS) and nonionic (TX-100)) mixture in aqueous and aqua-organic mixed solvents have been investigated applying the conductivity, cloud point, and UV–visible spectroscopic methods. In the current study, the various physico-chemical parameters (critical micelle concentration (CMC), extent of bound counter ions, cloud point (CP), binding constant (Kb), thermodynamic properties, and transfer parameters) were determined. The addition of SA facilitates SDS micellization. The CMC of the SA + SDS mixtures were obtained to be dependent on SA concentration, composition of mixed solvents, and temperature. The CMC of the SA + SDS mixture were found to be greater in magnitude in aqua-organic (dimethyl formamide (DMF), acetonitrile (AN), ethylene glycol (EG), and 1,4-dioxane (DX)) mixed solvents than the values observed in H2O medium. The values of counterion binding were found to be enhanced with the boost of concentration of SA and other organic additives. The Kb values of SA + TX-100 mixtures were computed from the Benesi-Hildebrand (BH) plot and the Kb values were found to be temperature-dependent. The CP values of the SA + TX-100 mixture experienced a lessening with growing contents of SA and got enhanced in diols (EG/ propanediol (PrD)) media. The negative values of free energy changes dictate that the micellization of SA + SDS mixture and binding processes for the SA + TX-100 mixture are spontaneous in nature while the positive free energy changes indicate the non-spontaneity of clouding phenomena of SA + TX-100 mixture. The obtained values of enthalpy and entropy changes recommend the presence of hydrophobic, electrostatic, and ion–dipole interactions amongst SA and SDS while hydrogen bonding, ion–dipole, and van der Walls forces are the proposed forces between SA and TX-100. Excellent enthalpy–entropy compensation was observed in each case.

A block copolymer poly(ethylene glycol)-b-poly(vinylbenzyltrimethylammonium triflate), PEG-PVBTMA-OTf, and a homopolymer PVBTMA-OTf were synthesized through RAFT reactions. The polymers were studied in aqueous triflate solutions with varying temperatures, changing also the polymer and salt concentrations. The hydrophobic triflate anion turns polycations thermoresponsive, and they show an UCST. In the block copolymer, the interaction between the PEG and the cationic block makes the phase separation occur in distinct steps. Upon cooling, transparent solutions first turn turbid and then partially clear at T cL. The T cL is not observed in a mixed solution of PVBTMA-OTf and PEG macro-CTA. By considering the interplay between ionic, hydrogen bonding, and hydrophobic interactions, an overall picture of the complex phase separation processes is suggested.

In this research, porous hollow fiber membranes for DCMD desalination were fabricated by non-solvent induced phase inversion. The membrane materials were PVDF 6010 and its blend with P(VDF-co-HFP), expected to combine the advantages of each material. It was found that with higher P(VDF-co-HFP) content in the blend, the membrane materials acquired stronger hydrophobicity. The maximum tensile strength was obtained with hollow fibers having 30% P(VDF-co-HFP), which was 2.86 MPa. Cloud point test showed that the one phase region of the solution with neat P(VDF-co-HFP) was closer to the polymer-solvent axis in the phase diagram, indicating a lower thermodynamic stability of this polymer solution. The varied degree of the liquid/liquid demixing and the solid/liquid demixing induced by changing P(VDF-co-HFP) content might be the underlying factor causing the dissimilarities in the above membrane structural and mechanical characteristics. DSC was employed to corroborate the crystallinity of the membranes. The DCMD tests using NaCl aqueous solution showed that membranes with higher PVDF 6010 content provided apparently higher flux. Stable salt rejection above 99% were obtained with all the membranes under the operation conditions investigated.

Formation of gas hydrates is a major problem in flowlines where gas and water are transported together, and can lead to blockages, downtime, economic losses, and potential accidents. One way of preventing gas hydrates from forming is by injection of kinetic hydrate inhibitors (KHIs). KHIs are typically water-soluble polymers, often containing amide pendant groups. Based on our previous work on high cloud point polymers of N,N-dimethylhydrazidoacrylamide (polyDMHAM) and N,N-dimethylhydrazidomethacrylamide (polyDMHMAM), we have now synthesized a series of N-(pyrrolidin-1-yl)methacrylamide polymers (polyNPyMA) which contains a pyrrolidine-substituted hydrazido pendant group. These polymers show improvement on all previous hydrazido polymers as they exhibit improved KHI performance while having no cloud point in deionized water or 7 wt % aqueous NaCl up to 95 °C. Their performance as KHIs have been investigated using a high-pressure gas hydrate rocker rig at a pressure of 76 bar using a structure II forming n...

The biggest problem in homogeneous catalysis is how to devise efficient recycling of the catalyst in its active form. In this contribution, cloud point extraction (CPE), a methodology already known from different applications, is adapted for the recycling of homogeneous catalysts from micellar solutions. About 96% of a homogeneously dissolved Rh/BPPM catalyst complex is recycled by CPE from aqueous micellar solutions of the nonionic surfactant NP8 and reused in subsequent reactions. The hydrogenation of itaconic acid is studied as a benchmark reaction to prove this alternative concept showing that it is feasible for catalyst recycling. However, severe catalyst deactivation takes place for substrates with carboxylic acid groups, which needs consideration during substrate selection.

Nonionic surfactant aqueous two-phase systems represent an alternative extracting media to conventional organic solvents by ensuring a mild process temperature in an aqueous environment. However, their large-scale implementation is limited due to the challenging stripping of the target substances from the surfactant. In this study, we demonstrate the application of aqueous food-grade and cosmetic-grade surfactant systems as extraction media for solutes of natural origin. We suggest that no separation of surfactant and target product (or only rough separation is sufficient) is needed in this case due to the application of both substances in the final food or cosmetic formulation. To this purpose, sixteen potential commercial surfactants applied in food or in the personal care industry were investigated for their cloud point temperature and their phase separation kinetics. Among those, the aqueous surfactant systems containing Silwet L-7230 (poly[dimethylsiloxane-co-methyl(3-hydroxypropyl)siloxane]-graft-poly(ethylene/propylene glycol) and ROKAnol NL5 (C9–11, branched and linear, ethoxylated alcohol) separated in two phases rapidly at temperatures below 50 °C. Therefore, the liquid-liquid equilibria of the mixtures Silwet L-7230/water and ROKAnol NL5/water were determined, exhibiting lower critical solution temperatures (LCSTs) of 37.3 °C and 33.5 °C, respectively. Additionally, the mixtures were investigated for their capacity to extract the model solute cinnamic acid ((2E)-3-phenylprop-2-enoic acid, CA). Batch separations with 10 logP CA = 0.9 for ROKAnol NL5 and 10 logP CA = 1.6 for Silwet L-7230 were achieved, proving the potential of these surfactants for the extraction of hydrophobic compounds. To further design a stable liquid-liquid extraction process, the density and viscosity of the surfactant-water mixtures were measured. The density differences between the micellar and aqueous phases was found to be sufficient for continuous extraction, whereby the system with ROKAnol NL5 consisted of an upper surfactant-rich phase and a lower surfactant-lean phase, and vice versa for the Silwet L-7230 system. The formation of a liquid crystalline structure with high viscosity was observed in the Silwet L-7230 micellar phase. Based on these investigations, the corresponding processes were designed and finally, for the first time, the food-grade Silwet L-7230 and the cosmetic-grade ROKAnol NL5 surfactant systems could be successfully implemented in the batch (yield = 77% and 80%) and in the continuous (yield = 96% and 100%) cloud point extraction of cinnamic acid.

This paper accomplishes a broad survey of the salting effects of different ammonium salts on the aqueous polymer solutions. In order to cover a wide range of hydrophilic and hydrophobic nature of solutes, salts including ammonium chloride (NH4Cl), ammonium bromide (NH4Br), tetraethyl ammonium bromide (TEAB), tetrapropyl ammonium bromide (TPAB), tetrabutyl ammonium bromide (TBAB), tetrabutyl ammonium chloride (TBAC), and dodecyl trimethyl ammonium bromide (DTAB), and polymers polyethylene glycol (PEG400 and PEG10000) and polypropylene glycol (PPG400 and PPG1000) have been used. In the first part of this work, cloud point temperatures (TC) for binary system of PPG1000 in pure water and for ternary systems of PPG1000 in aqueous solutions of ammonium salts have been determined by visual observation. It is shown that while the inorganic ammonium salts (NH4Cl and NH4Br) reduce the TC values of PPG1000 aqueous solutions (salting-out effect), the organic ammonium salts (TEAB, TPAB, TBAB, TBAC, DTAB) because of hydrocarbon portions in their structure favourably interact with PPG1000 and elevate the TC values (salting-in effect). The values of salting coefficient and energetic parameters of clouding process have been calculated. In the second part of this work, the isopiestic equilibrium has been investigated for several ternary {polymer + ammonium salt + water} systems at 298.2 K. Three different types of constant water activity curves deviation from the linear isopiestic relation (LIR) were observed: negative deviations for systems which undergo salting-out phenomenon and phase separation, positive deviations for systems which undergo salting-in effect, and non-deviation for semi-ideal solutions. The effects of type and molar mass of polymers, and type of cation and anion of ammonium salts on the magnitude and type of salting effects have been scrutinized.

Cloud point extraction (CPE) method was successfully used for estimation and preconcentration of Allura red (E129) by spectrophotometry. The procedure was depended on the extraction of Allura red as an ion pair with cetyl pyridinium chloride from aqueous solution using a nonionic surfactant TX-114 or Brij-35. The absorbance of the extracted surfactant- rich phase was measured at 507 nm after diluted with water.The influence of different factors on cloud point extraction(CPE) of Allura red such as pH media ,equilibrium temperature ,incubation time , concentration of surfactant and electrolyte concentration was investigated.Calibration graph was linear in a concentration range between 2-40 µgml-1 of Allura red with correlation coefficient r= 0.9998 for TX-114 and 0.9992 for Brij-35 .The developed procedure was applied to estimation and preconcentration of Allura red in the different beverages

It is reported in literature that zinc (Zn2+) has antidepressant activity. In present study Zn2+ was analyzed in blood serum of male patients having various psychiatric disorders (schizophrenia, depression, bipolar). As it is usually present in trace levels. Hence a novel, environmental friendly, dual-cloud point extraction (d-CPE) method was developed for the enrichment of its trace levels in acid digested serum samples. In the first step of d-CPE, Zn2+ was complexed with 1-(2-pyridylazo)-2-naphthol (PAN), and the complex was entrapped in a nonionic surfactant (Triton X-114). After achieving cloud point by heating, the mixture was separated into two layers i.e. aqueous and surfactant-rich by centrifugation. In second step of d-CPE, the analyte complex in the surfactant-rich phase was treated wih acid to extract back the metal analytes in acidic aqueous phase, the mixture was again heated upto cloud point and the whole procedure was repeated. This time the aqueous phase, having the metals, was taken and subjected to FAAS using conventional nebulization. The accuracy of the developed methodologies (conventional and d-CPE), were verified by their application to certified reference material of serum (CRM). Reliability of the method was checked by relative standard deviation (%RSD), which was found to be

We report unusual thermoresponsive behaviors of one poly(N-isopropylacrylamide) (PNIPAm)-based diblock copolymer containing carboxylic azo moieties due to the introduction of one charged end-group. On heating, the ionized end-group prevented macroscopic phase separation of the block copolymer aqueous solution under basic conditions, leading to the absence of cloud point. The micelle solution showed a quick micelle-to-vesicle morphological transition via the end-group stabilized large micelles as a transition state when being stored at 50 °C for 2 h. Such a quick micelle-to-vesicle transition can be attributed to the joint effect of the charged end-group stabilization and the changed hydrophilic–hydrophobic balance of PNIPAm. When adding a tiny amount of Ca2+, macroscopic phase transition reoccurred by breaking the end-group protection layer. This study represents a unique separation of microscopic dehydration and macroscopic phase transition, providing a new way for design of stimuli-responsive polymers.

Cloud point extraction has been shown to be an effective technique to remove hydrophobic volatile organic compounds (HVOCs) from aqueous solution using nonionic surfactant. A cocurrent vacuum strip...

This work investigates the effect of various additives/compounds present in fermentation media and products on phase transition temperatures [cloud point (CP), melting point (MP), double cloud point (DCP) and phase separation temperature (PST)] of non-ionic surfactant. Butanol fermentation media and L62 (tri-block copolymer) were considered as a model system. Results showed that the phase transition temperatures strongly depend on concentration of surfactant, butanol and glucose. Phase transition temperature (CP, MP, DCP, and PST) for control i.e. aqueous solution of L62 (3%–15% v/v) were 295–299 K, 297–307 K, 317–322 K, 342–343 K, respectively. Butanol (1%–5% v/v) significantly decreased the phase transition temperatures (7–8 K, 8–11 K, 8–12 K, and 27–29 K, respectively for CP, MP, DCP, and PST) followed by glucose (2–3 K, 2–3 K, 2–7 K and 5–6 K respectively for CP, MP, DCP, and PST) whereas other additives have negligible effect. Presence of both glucose and butanol together had synergistic effect on depression of phase transition temperatures of L62 (9–10 K, 10–14 K, 9–10 K, and 27–29 K, respectively for CP, MP, DCP, and PST). The results from this study provide the estimation of typical cloud point temperature for a range of components present in fermentation media/products. Further, these results will be useful for deciding the conditions for cloud point extraction.