Oxyethylene Content Research Articles

H3PO4‐induced micellization of styrene‐ethylene oxide block copolymers in toluene solutions

AbstractIn toluene/dimethoxyethane (80/20)v solution, copolymers containing 11, 33, and 51 mol% of oxyethylene residues and having a fixed PS‐segment molecular weight of ~60,000 g/mol, are dissolved molecularly. Doping with 10, 20, and 50 mol% of H3PO4 based on the oxyethylene content, induces varying degrees, of micellization in the respective block copolymer solutions. Light scattering and viscometry were used to evaluate the relationship between block‐copolymer composition and the state of aggregation for solutions of styrene/ethylene oxide block copolymers as a function of solution concentration and level of doping with phosphoric acid. Specifically, diffusion coefficients, hydrodynamic radii, and critical micelle concentration were evaluated by dynamic light scattering. Radii of gyration were obtained by complementary static light scattering measurements. In all three block copolymers, complete micellization is realized at the 50 mol% H3PO4 doping level. At the 20 mol% H3PO4 doping level, complete micellization is induced with the copolymers containing 11 and 33 mol% of oxyethylene residues.

Exploiting self-assembled soft systems based on surfactants, biopolymers and their mixtures for inhibition of Citral degradation under harsh acidic Conditions

The chemical instability of Citral in acidic conditions is viewed as hurdle to commercialize it in food/beverage industries. We attempted to stabilize citral in various single and mixed surfactant systems at pH 1.0 and temperature 25 °C. The study highlights the importance of amount and density of positive charge of cationic surfactants and oxyethylene content of nonionic surfactants at the interface of self-assembly in inhibiting citral degradation. The hybrid of Chitosan and P123 showed a significant increase in the half-life of citral compared to that in its individual components. The results of the study suggest that it is possible to stabilize citral in strong acidic environs having a pH as low as 1.0 using mixed surfactant or polymer-amphiphile systems with significant positive charge/number of oxyethylene in their single components. Such polymer-surfactant systems formulations if biocompatible/food grade may act as promising media to enhance shelf life of citral.

Preparation, Characterization and Pharmacodynamic Evaluation of Fused Dispersions of Simvastatin using PEO-PPO Block Copolymer.

The solubility enhancement of poorly soluble compounds is an important task in pharmaceutical technology as it leads to better bioavailability and a more efficient application. Fused dispersions (FDs) of simvastatin (SIM) using PEO-PPO block copolymer were prepared which paved the way for the formation of an amorphous product with enhanced dissolution and bioavailability. The accumulative solubility of simvastatin (SIM) from PEO-PPO block copolymer (Lutrol NF 127 prill surfactant) was found to be superior to the drug alone which may be due to the increased oxyethylene content that played the major role in solubility enhancement. A 3(2) full factorial approach was used for optimization wherein the temperature to which the melt-drug mixture cooled (X1) and the drug-to-polymer ratio (X2) were selected as the independent variables and the time required for 90% drug dissolution (t90%) was selected as the dependent variable. A low level of X1 and a high level of X2 were suitable for obtaining higher dissolution of SIM from SIM FDs. On increasing melt to cool drug temperature, t90% increased thus improving dissolution rate of FD2 batch with the maximum drug release (99.63%) in 120 min. The optimized FDs were characterized by saturation solubility study, drug content, in-vitro dissolution, fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, x-ray diffraction, (1)HNMR spectroscopy and pharmacodynamic evaluation. Capsules containing optimized FDs were prepared and compared with marketed brand (SIMVOTIN®). Finally, it can be concluded that the optimized FDs of SIM ameliorate the solubility and dissolution of drug with improved pharmacodynamic activity.

Adsorption of nonionic surfactants and model HEUR associative thickeners on oligomeric acid-stabilized poly(methyl methacrylate) latices

Abstract The adsorption and competitive adsorption of nonionic oxynonylphenols (average oxyethylene units 12, 40 and 100), and model hydrophobically-modified ethoxylate urethane (HEUR) thickeners onto model poly(methyl methacrylate-methacrylic acid) P(MMA-MAA) latices were studied in terms of hydrophobicity of adsorbates (hydrophobe size and concentration), oxyethylene chain length, pH, and latex surface acid concentration. The adsorption isotherms of the nonionic surfactants on oligomeric acid-stabilized P(MMA-MAA) latices can be described by the Langmuir equation. For nonionic surfactants, the pH value had a significant effect on adsorption behavior. At pH 6, the amount of the surfactants adsorbed increases as the surface-acid concentration increases (e.g. 15–20% higher than that on acid monomer-free latex for NPO(EtO) 12 H). At pH 9.5, the adsorption of NP(EtO) 12 H decreases with increasing surface acid concentration. This reverse in trend, however, was not observed with the surfactants having higher oxyethylene content, and at both neutral and alkaline conditions, greater adsorption on acid-stabilized latices than on acid-monomer-free latices was observed with all HEUR thickeners studied. This was supported by electrokinetic measurements. The competitive adsorption between the nonionic surfactant C 9 H 19 C 6 H 4 O(EtO) 12 H and model HEUR associative thickeners onto model P(MMA-MAA) latices was investigated in relation to the structure of the HEURs. Structural variables include terminal-hydrophobe size and the architecture of the internal connecting unit. The amount of surfactant adsorbed is unaffected by the presence of poly(oxyethyle)e), but is significantly reduced as the effective size of the terminal hydrophobe of the thickener and the concentration of the HEUR hydrophobe are increased.

Interaction of Surfactant and Leaf Surface in Glyphosate Absorption

The effect of oxyethylene (OE) chain length of three homologous series of nonionic surfactants (allinol, nonoxynol, octoxynol) on glyphosate uptake was markedly affected by the leaf surface fine-structure of sugarbeet and kohlrabi. Adaxial leaf surfaces of sugarbeet were covered with a layer of amorphous wax, whereas the adaxial surface of kohlrabi leaves was covered with fine crystalline wax. Foliar uptake of glyphosate (1 mM glyphosate, 20 mM glycine, pH 3.2) averaged 4% for sugarbeet without surfactant, but droplets were not retained by kohlrabi leaves in the absence of a surfactant. Glyphosate absorption with octoxynol (9 to 10 OE units, 0.5 g L−1) was rapid initially (0 to 2 h) and leveled off about 2 h after application in both species. Absorption by sugarbeet decreased from 12 to 3% as OE content of octoxynol was increased from 5 to 30 OE units. In contrast, surfactants of intermediate OE content (octoxynol, 16 OE units) induced the greatest uptake (17%) on kohlrabi. Leaf wetting was markedly affected by surfactant and leaf surface. As OE content of octoxynol increased from 5 to 30 OE units, droplet/leaf interface areas of 1-μl droplets decreased from 4 to 3 mm2on the adaxial leaf surface of sugarbeet and from 61 to 2 mm2on kohlrabi. Concurrently, the rate of droplet evaporation (1 μl) decreased from 1.0 to 0.7 nl s−1on sugarbeet and 4.2 to 0.5 nl s−1on kohlrabi leaves. The effect of OE content on enhancement of glyphosate uptake and wetting characteristics of spray solutions was similar within species for different hydrophobic moieties but differed markedly between species.

Studies on octylphenoxy surfactants: IX. Effect of oxyethylene chain length on GA3 absorption by sour cherry leaves

The effect of a homologous series of octylphenoxy surfactants, α-[4-(1,1,3,3-tetramethylbutyl)phenyl]-ω-hydroxypoly-(oxy-1,2-ethanediyl), condensed with 5, 7–8, 9–10, 16, and 30 oxyethylene (EO) units on enhancement of gibberellic acid (GA3) absorption by leaves ofPrunus cerasus cv. Montmorency was studied. Increasing EO chain length (5–30 EO) increased surface tension (27.5–35.3 mN m−1) and contact angles on adaxial (21–36°) and abaxial (28–49°) leaf surfaces. With increasing EO content, the form of GA3 deposits from droplets on the leaf surface changed from an annulus shape (5 and 7–8 EO) to globular forms covering increasingly smaller interface areas (9–10 to 30 EO). The surfactants increased GA3 uptake, the magnitude decreased with an increase in oxyethylene chain length. Similar trends were found for both the adaxial and abaxial surfaces. Penetration through the abaxial surface was linearly related to the logarithm of the oxyethylene content of the surfactant molecule (r 2=0.934**) and to the hydrophilic: lipophilic balance (r 2=0.926**). Absorption by the abaxial surface was approximately one order of magnitude greater than by the adaxial surface.

The interaction of cultured cells with membranes composed of random and block copolypeptides.

Random copolypeptides and block copolypeptides were synthesized, and an interaction between these polypeptide membranes and the cells was studied by a cell culture method (cell line, Ca. 9.22). In random copolypeptides composed of gamma-methyl L-glutamate and gamma-benzyl L-glutamate, cell attachment and cell growth depended on the monomer composition, and showed a maximum at around 70 mole % of benzyl glutamate. Block copolypeptide composed of L-methionine and oxyethylene exhibited low cell attachment and cell growth even at 10 mole % of oxyethylene content, compared to L-methionine homopolymer. ESCA study of the membrane suggested this result to be due to concentration of the poly(oxyethylene) block chain of the polymer on the surface of the membrane. Block copolypeptide composed of N5-(3-hydroxypropyl) L-glutamine and L-leucine exhibited low cell attachment and cell growth, while the corresponding random copolypeptide exhibited high cell attachment and cell growth. This difference is attributable to the microheterophase structure with the hydrophilic domains embedded in the hydrophobic matrix in the block copolypeptide membrane.

Solubilization of tropicamide by poloxamers: physicochemical data and activity data in rabbits and humans

A series of polyoxyethylene-polyoxypropylene (POE/POP) block copolymers (Poloxamers, or Pluronics) were evaluated as solubilizers for tropicamide, a poorly water-soluble mydriatic/cycloplegic drug. The selected Pluronics were L64, P65 and F68 (POP weight 1750, POE weight 1150, 1650 and 6650, respectively), P75 and F77 (POP weight 2050, POE weight 2100 and 4550, respectively), P84, P85, F87 and F88 (POP weight 2250, POE weight 1950, 2350, 5450 and 9150, respectively) and F127 (POP weight 4000, POE weight 8600). The following studies were carried out: solubility of tropicamide in polymer solutions, partition coefficient of the drug between isopropyl myristate and polymer solutions, critical micelle concentration (CMC) of the polymers, viscosity of the polymeric solutions containing tropicamide, mydriatic activity tests on rabbits and humans, cycloplegic activity tests on humans. The solubility isotherms (25 °C) showed that the saturation solubility of the drug increased linearly with increasing surfactants concentration in the 4.0–20.0 w/v concentration range. In the presence of 20% w/v Pluronics the drug solubility increased substantially, ranging from 1.9 times (F88) to ca. 3.0 times (P85) the solubility in water at the same temperature (0.57 g/100 ml). Analysis of the solubility data indicated that the solubility of tropicamide increased as the oxyethylene content of the surfactants increased, and that the amount of drug solubilized per EO unit decreased with increasing hydrophilicity (increasing OE chain length) of surfactants. Calculation of the relative amount of drug bound to the POE and to the POP portions of the surfactant molecules indicated that binding occurs in part to the hydrophilic (POE) outer mantle, and in part to the hydrophobic, (POP) inner core of the micellar aggregates, with POE/POP binding ratios varying from 1.17 to 3.13, depending on the polymer type. Biological activity tests were carried out with some 15% w/v polymeric solutions (L64, P75, P84, P85 and F87) containing 1.0% w/v tropicamide, and with some 20.0% w/v solutions (P85, F87) containing 1 5 % w/v drug. The results indicate that tropicamide bioavailability, both in rabbits and in humans, was not decreased by micellar Solubilization, and that some Poloxamers can perform satisfactorily as solubilizing vehicles for tropicamide, producing neutral 1.0% and 1.5% drug solutions which are better tolerated and more effective than the standard aqueous eyedrops.

Studies on octylphenoxy surfactants. Part 1: Effects of oxyethylene content on properties of potential relevance to foliar absorption

AbstractSelected properties of octylphenol and seven of its ethoxylated derivatives were studied as a preliminary to investigating their effects on the foliar absorption of three model compounds and the surfactants themselves. Surface tension of the surfactants (2 g litre−1 in water) increased with their hydrophile:lipophile balance (HLB) which is a function of oxyethylene (EO) content. The surface tension of the aqueous surfactants was inversely related to the cosine of their contact angle (θ) on maize leaf in the EO range 7.5–30. Cos θ was in turn related to the wetting of maize by aqueous acetone solutions of surfactants with EO >9.5. The critical surface tension required for complete wetting of the adaxial surface of maize leaf was estimated to be 29 mN m−1. Evaporation of drops of aqueous acetone solutions was biphasic, with preferential loss of acetone during the initial, more rapid phase. The rate of evaporation from the remaining, effectively aqueous systems was inversely related to the HLB of the surfactants. Phytotoxicity of the surfactants, as measured by ethylene production, increased with decreasing EO, while their hygroscopic water retention increased with both log EO and relative humidity (r.h.). Aqueous solubilities of pentacosane, DDT and atrazine were increased up to 8‐fold by surfactant (20 g litre−1). Maximum solubilities were observed with surfactants having intermediate HLB values. The solubility of pentacosane (maximum 221 μg litre−1) indicated that the surfactants would probably not solubilise more than 0.1% of the epicuticular wax when applied to maize leaf. Scanning electron microscopic observation of leaf surfaces exposed to surfactants for 24 h did not reveal any visible modifications of the wax structure. Volatilisation of DDT was reduced in the presence of surfactants but that ofatrazine was increased, although in inverse proportion to its solubility in aqueous surfactant.

Effects of structural variations of non-ionic surfactants on micellar properties and solubilization: variation of oxyethylene content on properties of C22 monoethers.

Studies on erucyl alcohol ethoxylated with 40 and 47 units, and on behenyl alcohol ethoxylated with 33 and 43 units, gave values of 106, 101, 271, and 304 (all X 10(3)) for the micellar weight, 51,42,152, and 137 for the aggregation numbers, and 257,362,209, and 311 moles water mol-1 surfactant for the micellar hydration, respectively. Measurements of the solubilization of azobenzene, cortisone acetate, griseofulvin, sulphadiazine, phenylbutazone, betamethasone, tolbutamide, and menaphthone showed that the erucyl derivatives were better solubilizers than the behenyl compounds, and that solubilization increased as the polyoxyethylene chain was shortened; this change was more pronounced with the erucyl compounds.

Tensammetric determination of polyoxyethylenated alcohols with low oxyethylene content at parts-per-million concentrations

Tensammetric determination of polyoxyethylenated alcohols with low oxyethylene content at parts-per-million concentrations

Relationships between poloxamer structure and the solubilization of some para-substituted acetanilides.

Saturation solubilities of several para-substituted acetanilides have been measured at 37 degrees C in aqueous solutions of structurally related polyoxyethylene-polyoxypropylene block copolymers-poloxamers L62, L63, L64, P65 and F68. These poloxamers differ only in the amount of ethylene oxide in the hydrophil. Solubilities increased with increasing poloxamer concentration. As the oxyethylene chain length of the poloxamer increased, then the solubilizing capacity per equivalent of oxyethylene decreased. The moles of acetanilide derivative solubilized per mole of poloxamer increased with poloxamer oxyethylene content in the case of the less hydrophobic acetanilides but was invariant in the more hydrophobic ones. The solubilizing capacities have been discussed in terms of the inter-relationships between the hydrophobic nature of the solubilizate and solubilizer and the site of solubilization on the poloxamer molecule.

The determination of adjacent oxypropylene–oxyethylene units in propylene oxide–ethylene oxide adducts by infrared spectroscopy

AbstractA study of several base‐catalyzed propylene oxide—ethylene oxide adducts of glycerin and certain model compounds has shown that an infrared absorption band at 10.30 μ can be associated with a structural entity represented by an oxyethylene unit attached to an oxypropylene unit at the secondary position. Coupled with other information such as total oxyethylene content and primary hydroxyl content, this finding has proved most useful in differentiating average molecular structure for commercial polyether polyols used in the manufacture of polyurethanes.

Surface active block copolymers: I. The preparation and some surface active properties of block copolymers of tetrahydrofuran and ethylene oxide

AbstractA new type of surface active block copolymer (TE type) having the general formula HO(C2H4O)x(CH2. CH2CH2CH2O)y‐(C2H4O)zH, was obtained by addition of ethylene oxide to polyoxytetramethylene glycols with molecular weight of 1000‐3400. TE types in which the polyoxyethylene sections comprised more than 20–25% of the total weight are soluble in water, and the relation between cloud point and oxyethylene content for TE types was similar to that for propylene oxide‐ethylene oxide block copolymers (Pluronics). Some surface active properties of TE types were examined in comparison with those of Pluronics and some other surfactants. The surface tension, foaming and antifoaming properties of TE types were comparable to those of Pluronics. Although the wetting power of TE types was poor, their suspending power (for carbon black) was superior to that of Pluronics in both aqueous and nonaqeuous media. The addition of TE types to some conventional detergents enhanced significantly their detergency. TE types showed a remarkable demulsifying action, on addition to some W/O emulsions.

A modified method for the analysis of oxyethylene/oxypropylene copolymers by chemical fission and gas chromatography

A modification of the M athias-M ellor HBr fission/GLC method for determining the oxyethylene content of polyoxyethylene-polyoxypropylene copolymers is described, which eliminates arbitrary correction factors. The results are independent of molecular weight and oxyalkylene distribution of the materials and are within the limits of variation of commercial products, i.e., ± 1% at 50% oxyethylene and ± 0.1% at 3%. The reproducibility of replicate determination is normally better than this. Some of the disadvantages of infrared methods are also discussed.