Length scale of polyisopirene and dynamic light scattering and structure of sodium-2-diethylhexyl sulfosuccinate/water/decane

The mixture of polyisopirene (PI) and sodium-2-diethylhexyl sulfosuccinate /decane/water microemulsion (ME) at AOT to water molar ratio (X = 30) and droplet mass fraction (m_f,drop = 0.08) was studied with dynamic light scattering and small-angle X-ray scattering (SAXS). The light scattering was used to obtain the diffusion coefficient of Brownian motion of the nano-droplets at different polymer concentrations and molecular weights (1000 and 4700) in the ME. The dynamics of the nano-droplets decreased with the increase of molecular weight (from 1000 to 4700) and concentration (from 0.01 to 0.09) of PI. The study of the structure by SAXS showed that with increase of PI (MW = 1000) mass fraction from 0.01 to 0.09 at ME, the size of the droplets changes from 4.5 to 4.3 nm and with increase of PI (MW = 4700) concentration at ME, the size of droplets changes from 4.8 to 4.4 nm. The size ratio of droplets to polymer decreased with increase of concentration and molecular weight of polymer and also the interaction between the droplets increased with increase of polymer concentration.     

Extraction of cobalt by the AOT microemulsion system

The extraction of cobalt by Winsor II microemulsion system was studied. In the bis (2-ethylhexyl) sulfosuccinate sodium salt (AOT)/n-pentanol/n-heptane/NaCl system, AOT was used as a anionic surfactant to form microemulsion in n-heptane, n-pentanol was injected in the microemulsion as a cosurfactant. Co(II) was found to be extracted into the microemulsion phase due to ion pair formation such as Co²⁺(R–SO₃ ⁻)Cl. The influence of different parameters such as the volume ratio of aqueous phase to microemulsion, surfactant concentration, pH of the feed solutions, cosurfactant concentration as well as temperature on the extraction yield (E%) were investigated. The results showed that it was possible to extract 95% of cobalt by the AOT Winsor II microemulsion.     

Poly(N-isopropylacrylamide-co-N-t-butylacrylamide)-block-poly(ethylene glycol)-block-poly(N-isopropylacrylamide-co-N-t-butylacrylamide) triblock copolymers: synthesis and thermogelation properties of aqueous solutions

Novel triblock copolymers with PEG middle blocks of 1–10 kDa and poly(N-isopropylacrylamide-co-t-butylacrylamide) statistical copolymer side arms with DP_n?≈?88 and different compositions, were synthesized by SET-LRP. The thermogelation properties of their aqueous solutions depended on both hydrophobic monomer content of the side blocks and molecular weight (MW) of the poly(ethylene glycol) (PEG) middle block, as proven by dynamic rheometry, DSC, and tube inversion method measurements. At constant PEG chain length, increasing TBAM proportions led to a gelation process occurring at progressively lower temperatures, as well as to a lower stability of the forming hydrogels in the case of shorter-PEG-chain block copolymers. By employing longer PEG blocks (M_PEG ≥6,000 Da), stable hydrogels with the gelation temperature below 37 °C could be obtained. For a constant composition of the copolyacrylamide blocks, the dependence of the phase transition temperature (T_ph) on M_PEG displayed a different shape at different polymer solution concentrations, because of the stronger variation of T_ph with polymer concentration as M_PEG increased. Also, the viscoelastic properties of the hydrogels resulting from 20 wt.% polymer aqueous solutions at 37 °C were stronger affected by the MW of the PEG middle block than by the hydrophobic character of the thermosensitive side blocks.     

Light scattering and SAXS of spherical to cylindrical transition of AOT/H2O/cyclohexane/PI

The mixture of polyisoprene with sodium-2-diethylhexyl sulfosuccinate (AOT)/H₂O/cyclohexane microemulsion is studied with the photon correlation spectroscopy (PCS) and small angel X-ray scattering (SAXS). The water with AOT induces nano-droplets inside the cyclohexane and addition of concentration and length scale of polyisoprene (PI) can change diffusion of nano-droplets. The collective diffusion coefficient (D_c) of nano-droplets decreased with increase in concentration of PI. From SAXS experiment, a spherical–cylindrical transition of nano-droplets by increase in polyisoprene concentrations observed that it can describe behaviour of diffusion.     

Kinetics of the Oxidation of Phenylhydrazine by [Fe(CN)6]3− in Water‐in‐Oil Microemulsions

The oxidation reaction of phenyl hydrazine (Phh) by hexacyanoferrate ([Fe(CN)₆]^3?) has been studied in water‐in‐oil (w/o) microemulsion media. The kinetic profile of the reaction was investigated as a function of [Phh], droplet size, and droplet concentration. Comparison of the kinetic profiles of the reaction in microemulsion, water‐urea, and water‐AOT‐urea media indicates that the kinetic profile of the reaction in microemulsion shows a behavior similar to that of the reaction in water‐AOT‐urea medium at 4 M urea. An initial increase and then a decrease in k_obs is observed with increasing molar ratio, W_o(=[H₂O]/[AOT]) at constant [AOT] (=0.4 M), whereas k_obs decreases upon increasing the AOT concentration at constant molar ratio.     

Application of Dipotassium Glycoxides–Activated 18-Crown-6 for the Synthesis of Poly(propylene oxide) with Increased Molar Mass

Mono- and dipotassium salts of dipropylene glycol were applied for the polymerization of propylene oxide in mild conditions, i.e., tetrahydrofuran solution at ambient temperature. The structure of polymers was investigated by use of ¹³C NMR and MALDI-TOF techniques. The structure depends strongly on the kind of initiator and additives that are used such as coronand 18-crown-6 and dipropylene glycol. The lowest unsaturation, represented by allyloxy starting groups, has the polymer obtained by use of monopotassium salt without the ligand. The highest unsaturation degree is for the polymer synthesized in the presence of dipotassium salt–activated 18-crown-6. This polymer, obtained at high initial monomer concentration and low initial concentration of initiator, consists of two fractions, i.e., a low molar mass fraction (M_n = 9400) containing mainly macromolecules with alkoxide starting and end groups and a much higher molar mass fraction (M_n = 29500 g/mol) containing macromolecules with allyloxy starting groups and alkoxide or hydroxyl end groups. Addition of free glycol to this system decreases the molar mass of polymers. Similar results were obtained by use of dipotassium salts of other glycols. The mechanisms of the studied processes are discussed.     

CHEMOENZYMATIC SYNTHESIS OF BIODEGRADABLE POLY(1’-O-VINYLADIPOYL-SUCROSE)

t A novel polymer containing the sucrose group was synthesized by radical polymerization from an enzymaticallyprepared monomer, l'-O-vinyledipoyl-sucrose (VAS). Transesterification reaction of sucrose with divinyl adipate inanhydrous pyridine catalyzed by an alkaline protease from Bacillus subtilis at 60℃ for 7 days gave VAS (yield 55%) withoutany blocking/deblocking steps. The vinyl sucrose ester could be polymerized with potassium persulfate and H_2O_2 as initiatorto give poly(l'-O-vinyladipoyl-sucrose) with M_n = 33,000 and M_w = 53,200, M_w/M_n = 1.61. The polymer was biodegradable.After 6 days in aqueous buffer (pH 7), this alkaline protease could degrade poly(l'-O-vinyladipoyl-sucrose) to M_n of ca.1080, M_w/M_n = 3.30 (37℃), and M_n of ca. 5200, M_w/M_n = 2.44 (4℃). The polymer containing the sucrose branch would be afunctional material in various application fields.     

Polymer diffusion in high-M/low-M hard-soft latex blends

This paper describes experiments that investigate the use of low glass transition temperature (T _g) latex particles consisting of oligomer to promote polymer diffusion in films formed from high molar mass polymer latex. The chemical composition of both polymers was similar. Fluorescence resonance energy transfer (FRET) was used to follow the rate of polymer diffusion for samples in which the high molar mass polymer was labeled with appropriate donor and acceptor dyes. In these latex blends, the presence of the oligomer (with M _n = 24,000 g/mol, M _w/M _n = 2) was so effective at promoting the interdiffusion of the higher molar mass poly(butyl acrylate-co-methyl methacrylate; PBA/MMA = 1:1 by weight) polymer (with M _n = 43,00 g/mol, M _w/M _n = 3) that a significant amount of interdiffusion occurred during film drying. Additional polymer diffusion occurred during film aging and annealing, and this effect could be described quantitatively in terms of free-volume theory. This paper is dedicated to Professor Haruma Kawaguchi to honor his many contributions to the field of latex particles and their applications.     

Droplet Exchange Kinetics in Microemulsions

The dynamic behavior of water-in-oil microemulsions (w/o), stabilized by sodium bis (2-ethyl-hexyl) sulphosuccinate (AOT), has been studied by means of stop flow method using spectroscopic detection. Kinetic model based on the ferroferric reaction was developed. Interdroplet exchange rate constant, k _ex , associated with the exchange of materials upon collisions between droplets in w/o microemulsions system has been determined. k _ex increases with increase in the chain length of linear alkanes and decreases with the water to surfactant molar concentration ratio (w ₀ = [H ₂ O]/[AOT]) and decreases in presence of viscosity modifier.     

Improvement in enzyme activity and stability by addition of low molecular weight polyethylene glycol to sodium bis(2-ethyl-L-hexyl)sulfosuccinate/isooctane reverse micellar system

The activity and stability of Chromobacterium viscosum lipase (glycerolester hydrolase, EC 3.1.1.3)-catalyzed olive oil hydrolysis in sodium bis (2-ethyl-1-hexyl)sulfosuccinate (AOT)/isooctane reverse micelles is increased appreciably when low molecular weight polyethylene glycol (PEG 400) is added to the reverse micelles. To understand the effect of PEG 400 on the phase behavior of the reverse micellar system, the phase diagram of AOT/PEG 400/water/isooctane system was studied. The influences of relevant parameters on the catalytic activity in AOT/PEG 400 reverse micelles were investigated and compared with the results in the simple AOT reverse micelles. In the presence of PEG 400, the linear decreasing trend of the lipase activity with AOT concentration, which is observed in the simple AOT reverse micelles, disappeared. Enzyme entrapped in AOT/PEG reverse micelles was very stable, retaining>75% of its initial activity after 60 d, whereas the half-life in simple AOT reverse micelles was 38 d. The kinetics parameter maximum velocity (V _max)exhibiting the temperature dependence and the activation energy obtained by Arrhenius plot was suppressed significantly by the addition of PEG 400.     

CO2-Switchable Nanoemulsion Based on N,N-dimethyl Oleoaminde-Propylamine (DOAPA) and Sodium Dodecyl Sulphate (SDS)

This research reported a CO₂-switchable nanoemulsion that was formulated by dilution of water in oil microemulsion, which was formed by mixture of N,N-dimethyl oleoaminde-propylamine (DOAPA), sodium dodecyl sulphate (SDS), n-hexane, n-butanol, and water. A reversible switch process was observed between a monophasic nanoemulsion and complete phase separation at R = 1:1 with the CO₂ and N₂ bubbling alternately. The phase separation was not found, but the reversible switch between single phase nanoemulsion was detected by zeta potential, electrical conductivity, and dynamic light scattering at R = 1:1.5 and 1.5:1.     

Dynamic properties of the polyethylene glycol molecules on the oscillating solid–liquid interface

The dynamic properties of polyethylene glycol (PEG) molecules on the solid–liquid interface oscillating at MHz were investigated using the quartz crystal microbalance (QCM). The number-average molecular weights (M_n) of the PEG molecules were systematically varied over 4 orders of magnitude. This study makes it clear that the series-resonant frequency shift, ΔF, of the QCM against the square root of the density–viscosity product of the PEG solution is linear and has the intercept. Moreover, systematical analysis reveals that the ΔF slope rapidly decreases with M_n and that the ΔF intercept becomes constant above 4.0 × 10³ g mol⁻¹. As a result, those reveal that the resonant length of the PEG molecule moving with the oscillating plate of 9 MHz is 54.2 Å. We also find that the behaviors of ΔF due to M_n are mainly caused by the length of the PEG molecule.     

Excess enthalpies for n-alkane/ -carotene+n-alkane/AOT/water systems

The experimental data of excess enthalpies for β-carotene/n-alkane+n-alkane/AOT/water systems at 298.15 K are reported. The H_E dependence on AOT (sodium bis(2-ethylhexyl) sulfosuccinate) concentration and hydrocarbon chain length was investigated. The excess enthalpy was measured using the flow microcalorimeter UNIPAN type 600.     

Kinetics for the Reaction between Potassium Ferricyanide and Cobalt Chloride in Aqueous Solution and Microemulsion

The kinetics for the reaction between potassium ferricyanide (K₃Fe(CN)₆) and cobalt chloride (CoCl₂) in aqueous solution and water/bis(2-ethylhexyl) sodium sulfosuccianate (AOT)/isooctane microemulsions were studied by three-wavelength spectrophotometry at 298.2 K. The second-order rate constants (k₂) were calculated from the time dependence of the concentration of reactant K₃Fe(CN)₆. The result showed that the reaction rates in water/AOT/isooctane microemulsions were slower than that in the aqueous solution, and k₂ decreased with molar ratio (ω) of water to AOT in microemulsions, which was interpreted by the transition state theory and confirmed that the reaction took place at the interfaces of the microemulsion water pools.     

Studies on the E7 liquid crystal orientations confined to perfluorinated carboxylic acid‐treated cylindrical cavities of Anodisc membranes by FTIR spectroscopy

The orientation of E7 liquid crystal (LC) confined within 200 nm diameter cylindrical cavities of Anodisc membranes are investigated by FTIR dichroism techniques. The cavity walls of the confining pores were chemically modified with different length perfluorinated carboxylic acids (PCAs, C _n F_2n+1COOH, n = 3, 4, 5, 6) at 1, 3 and 5 mM concentrations. From the FTIR spectra of PCA‐treated alumina Anodsic membranes, we found salt formation between the –COOH group of the PCAs and the Anodisc membranes. From the FTIR spectra of LC‐filled Anodisc membranes, we found an abrupt alignment direction change, from parallel to perpendicular, of the LC molecules along the long axis of the cavities between n = 4 and n = 5 for the 1 mM concentration of PCA. However, for the 5 mM concentration of PCA, the parallel‐to‐perpendicular alignment direction of LC molecules changed between n = 3 and n = 4. These LC orientation changes for PCA‐treated Anodisc membranes occurred at shorter length than for hydrocarbon carboxylic acid (HCA, C _n H_2n+1COOH)‐treated Anodisc membranes. This change may be caused by the lower surface energy of the –(CF₂) _n CF₃ chain of PCA than that of the –(CH₂) _n CH₃ chain of HCA.     

Influence of polyethylene glycols on percolative phenomena in AOT microemulsions

The influence of different polyethylene glycol (PEG) on the percolation of the ternary system composed by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) + isooctane + water has been studied. The additives used were chosen on the basis of its chain length (the number of polymeric units). In all cases, we observed a decrease in the percolation threshold on increasing the amount of PEG added to the AOT microemulsions. We observed a correlation between the effect exerted by the additive upon the percolation temperature and its chain length. Moreover, a relationship between the percolation temperature and the additive partition coefficient between 1-octanol and water (logP) was found. Both of them proved the importance of the inclusion of the additives into the microemulsion interface to explain their influence upon the percolative phenomenon. Such inclusion modified the properties of the AOT film, facilitating the exchange of matter between droplets.     

Polyethylene glycol-functionalized polyoctahedral silsesquioxanes as H+-conducting electrolytes

Proton-conducting electrolytes composed of a mixture of MePEG₇SO₃H acid and poly(ethylene) glycol-functionalized polyoctahedral silsesquioxanes (Q₈M₈-MePEG_n) are prepared. Eight MePEG_n (n?=?3, 7, and 12) arms are attached to a (HSiMe₂O)₈Si₈O₁₂ (Q₈M₈ ^H) core in the molecule. These Q₈M₈-MePEG_n compounds show nearly the same fractional free volume (FFV), but show increased volume fractions of PEG (V _f,PEG) and viscosities with longer PEG arms. At low MePEG₇SO₃H acid concentration (0.26 M), V _f,PEG and FFV dominantly affect the ionic conductivity. Q₈M₈-MePEG₁₂ shows the highest conductivity due to the largest V _f,PEG at 0.26 M. At a high acid concentration (1.32 M), the differences of V _f,PEG are much smaller and viscosity becomes more important. Q₈M₈-MePEG₃ reaches the largest conductivity of 1.32?×?10^?4 S cm^?1 at 55 °C at 1.32 M because of the lowest viscosity.     

Effects of prepolymer structure in holographic polymer dispersed liquid crystal

Three different types of polyols—poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG), and poly(tetramethylene glycol)—with different molecular weights (M_n) were incorporated into the prepolymer structure, and the effects were examined with regard to the morphology and performance of holographic polymer dispersed liquid crystal. Among them, PEG showing the lowest glass transition temperature (T_g) exhibited the lowest threshold voltage (V_th), lowest operating voltage (V_op), and lowest diffraction efficiency with slow grating formation owing to its high viscosity of prepolymer mixture. The T_g decreased with increasing M_n because of the decreased crosslink density and hydrogen bonding, which reduced the anchoring strength, V_th and V_op. PPG400 gave V_th and V_op of approximately 7 and 24 V, respectively, with a contrast ratio of approximately 12. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Solvent effect on the size of platinum nanoparticle synthesized in microemulsion systems

In this research work, the effect of solvent on the size of paltinum nanoparticles synthesized by microemulsion method was investigated. Platinum nanoparticles have been prepared by the reduction of H₂PtCl₆ with hydrazine in water-in-oil (w/o) microemulsions consisting of sodium bis(2-ethylhexyl) sulfo-succinate (AOT) and solvents n-hexane, cyclohexane and n-nonane. The size of the platinum nanoparticles was measured using transmission electron microscopy (TEM). It was verified that, for reduction of H₂PtCl₆ by hydrazine in microemulsion with different organic solvents, the solvents are arranged by their influence on nanoparticle sizes as follows: n-nonane > cyclohexane > n-hexane.     

Inclusion of Poly(ethylene glycol)s by Crystalline (R)-(1-Naphthyl)glycyl-(R)-phenylglycine

Abstract

Crystallization of (R)-(1-naphthyl)glycyl-(R)-phenyl-glycine [(R,R)-1] in the presence of oligo(ethylene glycol) dimethyl ethers 2(n) or poly(ethylene glycol)s (PEGs, 3(M_n )) afforded inclusion compounds. The ratio of (R,R)-1/the guest polymer (2 or 3) was proportional to the length of the polymer chain. The crystal structure of a hepta(ethylene glycol) dimethyl ether-included compound was disclosed by X-ray crystallography which showed that (R,R)-1 molecules form a sheet and the guest molecule penetrates the crystal lattice of (R,R)-1 through a one-dimensional channel on the sheet. Powder X-ray analysis revealed that, regardless of the length of the guest polymer, the distance between the neighboring sheets remains unchanged (12.0–12.3 Å) in these inclusion crystals. By thermal analysis, it was shown that the decomposition points of these inclusion compounds became higher with the longer PEG included. The inclusion phenomenon enabled the fractionation of PEGs with various molecular weights, among which longer PEG was preferably included.