Number Of EO Units Research Articles

General adsorption isotherm for polyoxyethylene alkyl ethers CnEOm adsorbed at the water/air surface

An empirical adsorption isotherm model is presented based on fundamental thermodynamic equations of adsorption for the homologous series of the nonionic surfactants polyoxyethylene alkyl ethers (CnEOm) at the aqueous solution surface to determine the surface tension and surface pressure isotherms, surface equation of state, and molar characteristics for the adsorbed surfactant molecules. The new model describes the surface properties of CnEOm much better than the original Langmuir adsorption model used as thermodynamic basis. The analysis of the results shows that the increase of the alkyl chain length n (hydrophobic part) leads to an increase in the adsorption activity, while the increase of hydrophilic head group given by the number of EO units m, leads to a better solubility in water, and hence, to a smaller adsorbed amount. The results also show that the ethylene oxide group mainly influences the molar surface area.

The hydrophilic-lipophilic balance of carboxylate and carbonate modified nonionic surfactants

The shift of the phase inversion temperature (PIT) of n-octane/water nonionic surfactant (C13EO5) emulsions was studied as a function of increasing amounts of an additional second surfactant in order to rank them according to their hydrophilic-lipophilic-balance. Two different groups of modified nonionic surfactants were investigated with the objective to quantify the contribution of the modified groups to the HLB value of the surfactants. One modification was obtained by copolymerization of ethylene oxide and CO2 for the synthesis of the hydrophilic head group. The second was the capping of the head group with a −CH2−COOH group. Well-defined polyethoxylated alkyl surfactants (CiEj) show a linear variation of the PIT with their mole fraction X2 and can be used as standards to calibrate a scale in terms of dPIT/dX2. With this method, it can be shown that the −CH2−COOH decreases the HLB value in comparison to an unmodified version of the same surfactant when measured at acidic pH values. The modification with CO2 increases the HLB value almost in the same way as the addition of the same number of EO units. This observation reveals the potential of a replacement of EO by CO2 to a certain extent, saving fossil resources, reducing the carbon footprint of the products and introduces a new tuning parameter for chemical and physical properties of the new group of surfactants.

Effect of Oxyethylete Units on Adsorption and Micellization Properties of Novel Benzene Sulfonate Surfactants

The surface tension and fluorescence spectra of sodium octyl-[ω-octyloxy-poly(oxyethylene)]-yl-benzene sulfonates (APEnBS) aqueous solutions have been investigated by Wilhelmy plate method and intrinsic probe methods, respectively to study the effect of EO units on their properties. It was discovered that the surface performance of these surfactants was greatly outstanding: the values of critical micelle concentration (CMC) reached to be of the order of magnitude of 10−5 mol/L, the values of surface tension at CMC, γCMC, were between 25.79 to 31.02 mN/m, and the effectiveness and efficiency of surface tension reduction were excellent. The introduction of oxyethylene units to the surfactant molecule evidently improved the solubility of APEnBS. With the increase in EO units, the CMC slightly changed after the first decreased. On the other hand, the surface excess concentration at saturation, Γ max, decreased after the first increased and γCMC increased after the first decreased accordingly. The CMC determined by fluorescence spectra of intrinsic probe method were accorded with the CMC measured by surface tension method. The aggregation number N, characterized by quenching the fluorescence spectra with methyl viologen (MV2+) as the extrinsic quencher, gradually decreased first (from 0 to1) and then slightly changed (from 1 to 4) with increasing EO chain length. So we concluded that the appropriate number of EO units was the key factor to get the best physicochemical properties of APEnBS.

Lithium conducting ionic liquids based on lithium borate salts

The simple reaction of trialkoxyborates with butyllithium resulted in the obtaining of new lithium borate salts: Li{[CH 3(OCH 2CH 2) n O] 3BC 4H 9}, containing oxyethylene substituents (EO) of n = 1, 2, 3 and 7. Salts of n ≥ 2 show properties of room temperature ionic liquid (RTIL) of low glass transition temperature, T g of the order from −70 to −80 °C. The ionic conductivity of the salts depends on the number of EO units, the highest conductivity is shown by the salt with n = 3; in bulk its ambient temperature conductivity is 2 × 10 −5 S cm −1 and in solution in cyclic propylene sulfite or EC/PC mixture, conductivity increases by an order of magnitude. Solid polymer electrolytes with borate salts over a wide concentration range, from 10 to 90 mol.% were obtained and characterized. Three types of polymeric matrices: poly(ethylene oxide) (PEO), poly(trimethylene carbonate) (PTMC) and two copolymers of acrylonitrile and butyl acrylate p(AN–BuA) were used in them as polymer matrices. It has been found that for systems of low salt concentration (10 mol.%) the best conducting properties were shown by solid polymer electrolytes with PEO, whereas for systems of high salt concentration, of the polymer-in-salt type, good results were achieved for PTMC as polymer matrix.

Competitive Intramolecular Hydrogen Bonding in Oligo(ethylene oxide) Substituted Quadruple Hydrogen Bonded Systems

A series of oligo(ethylene oxide) (oligoEO) substituted 2-ureido-pyrimidinones (UPy), differing in the number of ethylene oxide units and the length of the aliphatic spacer connecting the oligoEO side chain with the UPy group, have been prepared. It was found that variation in these structural parameters strongly influences the dimerization constant (K(dim)) of the UPy dimer and the association constant (K(a)) of UPy with 2,7-diamido-1,8-naphthyridine (NaPy) in chloroform. By analyzing the relation between dimerization strength, length of aliphatic spacer, and the number of EO units in the oligoEO chain, we present strong evidence that the reduction in hydrogen bond strength is caused by competitive intramolecular hydrogen bonding of the ether atoms of the oligoEO chain to the hydrogen bond donors of the UPy unit.

Protein-resistant polyurethane prepared by surface-initiated atom transfer radical graft polymerization (ATRgP) of water-soluble polymers: Effects of main chain and side chain lengths of grafts

Water-soluble poly(oligo(ethylene glycol) methacrylate) (poly(OEGMA)) with various main chain and side chain lengths were grafted to polyurethane (PU) surface by surface-initiated atom transfer radical graft polymerization (s-ATRgP). The polymer main chain length was varied by varying the molar ratio of monomer to free initiator in solution (typically 5:1, 50:1, 100:1). Three different side chain lengths were obtained using different OEGMA monomers (MW 300, 475, 1100 g/mol). Water contact angle and X-ray photoelectron spectroscopy (XPS) were used to characterize the modified PU surfaces. The respective effects of poly(OEGMA) main chain and side chain lengths on fibrinogen (Fg) and lysozyme (Lys) adsorption were investigated in single protein systems at room temperature in TBS, pH 7.4. The poly(OEGMA)-grafted PU surfaces were found to be highly protein-resistant, with reductions of Fg and Lys adsorption in the range of 84–98% and 67–91%, respectively, compared to the unmodified PU surface. The adsorption of both proteins decreased with increasing poly(OEGMA) main chain length for a given side chain length (number of EO units). For a given main chain length, the Fg adsorption level did not change significantly with increasing side chain length. However, Lys adsorption increased with increasing side chain length, possibly due to decreasing graft density as monomer size and footprint on the surface increase. Adsorption resistance was generally greater for the bigger protein.

Triblock Copolymers as Templates in Mesoporous Silica Formation: Structural Dependence on Polymer Chain Length and Synthesis Temperature

Mesoporous silica can be formed with amphiphilic molecules acting as structure-directing templates in dilute systems. The templating properties of five related triblock copolymers, (EO)x−(PO)y−(EO)x (Pluronic L101, P103, P104, P105, and F108), have been investigated regarding the length of the EO blocks as well as the temperature of the synthesis. It was found that the number of EO units is essential in determining which silica mesophase is obtained. Lamellar structure is obtained with short EO chains (4 units); hexagonal structure, with medium length EO chains (17−37 units); and cubic structure, with long EO chains (132 units). The hydrophobicity of the (EO)x−(PO)y−(EO)x polymer is strongly affected by the temperature. This is to some extent reflected in the silica mesostructure formed; a multilamellar vesicle morphology can be obtained at elevated synthesis temperatures. Also, the temperature has an influence on particle size.

Water sorption in polymer network films synthesised from PEO oligomers containing acrylic and vinyl ether functionalities

Poly(ethylene oxide) oligomers, with end groups that have either acrylic or vinyl ether functionalities, were photopolymerised by UV radiation to create polymer networks in the form of thin films. Moisture sorption of the polymers, determined by microgravimetric analysis, was correlated to the oligomer structure, i.e to the PEO chain length and to the type of unsaturation. The data can be described with a Fickian diffusion model using diffusion coefficients of water in the polymer networks on the order of 1 x 10 -12 m 2 /s. The total amount of water sorption at equilibrium saturation increases with an increasing number of EO units in the oligomer used to synthesise the network. The number of absorbed water molecules associated with each EO unit increases with the number of these units in the oligomer until it reaches two water molecules per EO unit, for acrylated-PEO oligomers (PEGDA) having at least 30 EO units. The type of interactions between the polymer network and water were evaluated by means of thermal analysis performed on the hydrated films. It was found that all water is present as bound rather than mobile water.

A facile antistatic modification of polyester fiber based on ion‐exchange reaction of sulfonate‐modified polyester and various cationic surfactants

AbstractA new technique for imparting antistatic properties to poly(ethylene terephthalate) (PET) fiber has been developed. In this technique, blend polyester fibers containing poly(ethylene terephthalate/5‐sulfoisophthalate) (SIP‐PET) were prepared by blend spinning and then treated with various cationic surfactants in the process of dyeing. The surfactants could effectively be immobilized on the fiber as the counter cations of the sulfonate groups of the 5‐sulfoisophthalate (SIP) units and aid the release of static electrons formed in the fiber. Thus, the half‐life time (t1/2) of leakage of static charge and the surface resistivity (Rs) of the blend PET fibers became much lower after treating. The best result was obtained with a methylated quaternary ammonium salt of a stearylamine‐ethylene oxide (EO) adduct or hydrochloride of a laurylamine‐EO adduct as the surfactant of which the number of EO units was around ten. Even after five washing cycles the t1/2 value of the fibers treated with these surfactants was kept lower than 30 s with the Rs value maintained in the order of 1013 Ω cm‐2. Therefore, the present technique could be useful for practical production of polyester fibers with “semi‐permanent” antistatic properties which can be recovered by re‐treatment even if they were lost.

Concentrated coal-water suspensions containing nonionic surfactants and polyelectrolytes 2. Adsorption of nonyl phenyl propylene oxide-ethylene oxide on coal and the rheology of the resulting suspension

Adsorption isotherms of a series of nonionic surfactants (Synperonic NPE) on coal showed a systematic decrease in the amount of adsorbed surfactant (Γ in μmol g −1) with increase in polyethylene oxide (PEO) chain length. A plot of Γ vs. n 1 2 (where n is the number of EO units) was linear indicating that the adsorbed amount is determined by the size of the PEO chain. Viscoelastic measurements on coal dispersions stabilized by these nonionic surfactants showed a rapid increase in the complex and storage moduli ( G ∗ and G′ respectively) at a critical volume fraction of coal, Φ cr. The latter was highest for the surfactant containing 48 EO units. The lower Φ cr obtained with the surfactant containing the shorter PEO chain (27 units) was due to the weak flocculation obtained with these dispersions. At longer PEO chains (79 and 174) desorption of the chains may occur and this results in greater flocculation. It was concluded that an optimum PEO chain length was required for maximum stability.