Abstract  RPSL-01 type photosensitive resin for Stereo lithography was prepared with 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate (UVR 6110), bisphenol A type epoxy diacrylate (EA-612), tripropylene glycol diacrylate (TPGDA), pentaerythritol triacrylate(PETA), triethylene glycol divinyl ether (DVE-3), benzil dimethyl ketal (Irgacure651) and a mixture of triarylsulfonium hexafluoroantimonate salts (UVI-6976) as raw materials. Some properties of the photosensitive resin were investigated. The viscosity of the photosensitive resin at 30 degrees C was 425mP(a).S, The glass transition temperature (Tg) of the UV-cured specimen was 47 degrees C, and the weight loss of the UV-cured specimen at 200 degrees C was less than 5%. The photosensitive resin and its UV-cured specimen were also characterized by infrared (IR).

Abstract  A new set of molar heat capacity data for aqueous {2-amino-2-hydroxymethyl-1,3-propanediol (TRIS) + glycol} at (30 to 80)degrees C and different concentrations (4% to 16% by weight TRIS or 56% to 44% by weight water, in a fixed amount of glycol - 40% by weight) were gathered via reliable measurement method and are presented in this report. The glycols considered were diethylene glycol (DEG), triethylene glycol (TEG), tetraethylene glycol (T(4)EG), propylene glycol (PG), dipropylene glycol (DPG), and tripropylene glycol (TPG). The 198 data points gathered fit the equation, C-p = C-p,C-a + B(1)m + B(2)m(2) + B(3)m(3), where C-p and C-p,C-a are the molar heat capacities of the (TRIS + glycol + water) and (water + glycol) systems, respectively, B-i the temperature-dependent parameters, and m the mole TRIS per kilogram (glycol + water). The overall average absolute deviation (AAD) of the experimental data from the corresponding values calculated from the correlation equation was 0.07%. (C) 2012 Elsevier Ltd. All rights reserved.

Abstract  Composites based on unsaturated polyester (UPe) resins and fumed silica AEROSIL (R) RY 50, NY 50, RX 50 and NAX 50, as well as graphite, TiO2 or organically modified clay CLOISITE 30B were prepared in order to investigate the influence of reinforcing agents on the mechanical properties of composites. Unsaturated polyester resins were synthesized from maleic anhydride and products of glycolysis, obtained by depolymerization of poly(ethylene terephthalate) with dipropylene glycol (UPe1 resin) and triethylene glycol (UPe2 resin) in the presence of tetrabutyl titanate catalyst. The obtained unsaturated polyesters were characterized by FTIR spectroscopy, acid and hydroxyl values, and their mechanical properties were also examined. Significant increase of the tensile modulus, tensile strength and decrease of the elongation at break was observed for composites prepared after addition of 10 wt.% of graphite or 10 wt.% of TiO2 to the UPe resins, indicating strong interaction between matrix and filler particles. On the other hand, nanocomposites prepared using UPe2 and hydrophobically modified silica nanoparticles showed lower tensile strength and tensile modulus than polymer matrix. The presence of CLOISITE 30B had no significant influence on the mechanical properties of UPe1, while tensile strength and tensile modulus of UPe2 increased after adding 10 wt.% of clay.

Abstract  The triethylene glycol and tripropylene glycol derivatives terminated with the CO2-philic phosphoryl groups, named 2-(2-(2-((2-ethylhexoxy(methoxy)phosphoryl)oxy)-ethoxy)ethoxy)ethyl 2-ethylhexyl methyl phosphate (EG3EH) and 2-(2-(2-((2-ethylhexoxy(methoxy)phosphoryl)oxy)propoxy)-propoxy)propyl 2-ethylhexyl methyl phosphate (PG3EH), were synthesized and characterized. The solubilities of EG3EH and PG3EH in scCO(2) were determined by a static method at temperatures from (313 to 333) K and over a pressure range of (10 to 19) MPa. The values calculated by the Bartle semiempirical model exhibited good agreement with the experimental data.

Abstract  The principal aim of the study was to estimate the level of exposure to organic solvents of graffiti removers, and to identify the chemicals used in different cleaning agents. A secondary objective was to inform about the toxicity of various products and to optimise working procedures.

Exposure to organic solvents was determined by active air sampling and biological monitoring among 38 graffiti removers during an 8-h work shift in the Stockholm underground system. The air samples and biological samples were analysed by gas chromatography. Exposure to organic solvents was also assessed by a questionnaire and interviews.

Solvents identified were N-methylpyrrolidone (NMP), dipropylene glycol monomethyl ether (DPGME), propylene glycol monomethyl ether (PGME), diethylene glycol monoethyl ether (DEGEE), toluene, xylene, pseudocumene, hemimellitine, mesitylene, ethylbenzene, limonene, nonane, decane, undecane, hexandecane and gamma-butyrolactone. The 8-h average exposures [time-weighted average (TWA)] were below 20% of the Swedish permissible exposure limit value (PEL) for all solvents identified. In poorly ventilated spaces, e.g. in elevators etc., the short-term exposures exceeded occasionally the Swedish short-term exposure limit values (STEL). The blood and urine concentrations of NMP and its metabolites were low. Glycol ethers and their metabolites (2-methoxypropionic acid (MPA), ethoxy acetic acid (EAA), butoxy acetic acid (BAA), and 2-(2-methoxyethoxy) acetic acid (MEAA)) were found in low concentrations in urine. There were significant correlation between the concentrations of NMP in air and levels of NMP and its metabolites in blood and urine. The use of personal protective equipment, i.e. gloves and respirators, was generally high.

Many different cleaning agents were used. The average exposure to solvents was low, but some working tasks included relatively high short-term exposure. To prevent adverse health effects, it is important to inform workers about the health risks and to restrict the use of the most toxic chemicals. Furthermore, it is important to develop good working procedures and to encourage the use of personal protection equipment.

Abstract  The addition of oxygen-bearing compounds to diesel fuel considerably reduces particulate emissions. TGME and DBM have been identified as possible diesel additives based on their physicochemical characteristics and performance in engine tests. Although these compounds will reduce particulate emissions, their potential environmental impacts are unknown. As a means of characterizing their persistence in environmental media such as soil and groundwater, we conducted a series of biodegradation tests of DBM and TGME. Benzene and methyl tertiary butyl ether (MTBE) were also tested as reference compounds. Primary degradation of DBM fully occurred within 3 days, while TGME presented a lag phase of approximately 8 days and was not completely degraded by day 28. Benzene primary degradation occurred completely by day 3 and MTBE did not degrade at all. The total mineralized fractions of DBM and TGME achieved constant values as a function of time of approximately 65% and approximately 40%, respectively. Transport predictions show that, released to the environment, DBM and TGME would concentrate mostly in soils and waters with minimal impact to air. From an environmental standpoint, these results combined with the transport predictions indicate that DBM is a better choice than TGME as a diesel additive.

Abstract  We carried out the decomposition reaction of a polyol [poly(propylene glycol), PPG] in supercritical water (380-430 degreesC, 10-90 min) to understand the reactivity of polyols at high temperature and pressure. The main products, hydroxyacetone and diols (propylene glycol, dipropylene glycol and tripropylene glycol), were identified and characterized by mass spectrometry (GC/MS). The yield of hydroxyacetone was 33.0 wt.% at 430 degreesC for 10 min and the total yield of hydroxyacetone and diols was 56.7 wt.% at 380 degreesC for 60 min. The effect of reaction conditions (temperature, time and pressure) on yields was examined. The investigation of PPG decomposition pathway demonstrated that hydroxyacetone was the end product and resulted from propylene glycol only. (C) 2003 Elsevier Science Ltd. All rights reserved.

Abstract  Survey of the literature on propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate, including their beta isomers, and dipropylene glycol monometyl ether. This document is to be used as background for the discussion of occupational exposure limits; it is recommended that the effects of irritation and reproductive toxicity be used in this discussion.

Abstract  The maternal and developmental toxicities of dipropylene-glycol-monomethyl-ether (20324327) (DPGME) were evaluated in rabbits and rats. The DPGME used was a commercial mixture of four isomers with a maximum theoretical yield of 61.8% of the beta isomer of propylene-glycol-methyl-ether (107982) (beta-PGME). New-Zealand-White-rabbits and Fischer-344-rats were used in the study. Groups of 16 inseminated rabbits or 32 to 37 bred rats were exposed via inhalation for 6 hours a day to 0, 50, 150, or 300 parts per million (ppm) DPGME on gestation days seven through 19 for rabbits and six through 15 for rats. No treatment related effects on the reproductive and fetal parameters recorded, or on the incidence of malformations or variations in fetuses were observed at any exposure level in either species. The exposure levels were not maternally toxic, embryo/fetotoxic or teratogenic. The authors conclude that since no developmental effects were observed in either rabbits or rats following exposure to 300ppm DPGME, the highest concentration of DPGME practicably attainable at room temperature and pressure, it is unlikely that sufficient atmospheric concentrations of DPGME could be generated to result in the formation of sufficient amounts of metabolite beta-PGME to represent a developmental hazard following DPGME exposure.

Abstract  A selective, sensitive, rapid and reliable method based on molecularly imprinted polymers (MIPs) with dual templates to determine total content of parabens in cosmetics was developed. With methylparaben (MP) and propylparaben (PP) as dual-templates, methacrylic acid (MAA) as a functional monomer and tripropylene glycol diacrylate (TPGDA) as a cross-linker, MIPs film on a glassy carbon electrode was constructed as paraben sensor. At oxidation potential of 0.94 V (vs. SCE), the peak currents on the MIPs sensor were proportional to the concentration of parabens with square wave voltammetry. As the ratio of MP to PP in the MIPs was 1:1.25, the regression equations for four parabens were almost the same. The linear range was 20-100 microM for MP and EP, 5-100 microM for PP, and 5-80 microM for BP, with detection limit of 0.4 microM for MP and EP, 0.2 microM for the others. The total content of parabens could be calculated according to the average of these four regress equations. At least 10 times of structural analogs, such as p-hydroxybenzoic acid, p-aminobenzoic acid and phenol would not interfere with the determination of parabens. Nonanalogous coexistences such as vitamin C had no response on the sensor at all. Rapid response of the MIPs sensor was obtained within 1 min. MIPs sensor had been used to determine total content of parabens in cosmetic samples with recoveries between 98.7% and 101.8%. It reveals that the MIPs sensor with multi-templates has a potential to determine the total content of a group of homologous compounds.

Abstract  Cleaning is a large enterprise involving a large fraction of the workforce worldwide. A broad spectrum of cleaning agents has been developed to facilitate dust and dirt removal, for disinfection and surface maintenance. The cleaning agents are used in large quantities throughout the world. Although a complex pattern of exposure to cleaning agents and resulting health problems, such as allergies and asthma, are reported among cleaners, only a few surveys of this type of product have been performed. This paper gives a broad introduction to cleaning agents and the impact of cleaning on cleaners, occupants of indoor environments, and the quality of cleaning. Cleaning agents are usually grouped into different product categories according to their technical functions and the purpose of their use (e.g. disinfectants and surface care products). The paper also indicates the adverse health and comfort effects associated with the use of these agents in connection with the cleaning process. The paper identifies disinfectants as the most hazardous group of cleaning agents. Cleaning agents contain evaporative and non-evaporative substances. The major toxicologically significant constituents of the former are volatile organic compounds (VOCs), defined as substances with boiling points in the range of 0 degree C to about 400 degrees C. Although laboratory emission testing has shown many VOCs with quite different time-concentration profiles, few field studies have been carried out measuring the exposure of cleaners. However, both field studies and emission testing indicate that the use of cleaning agents results in a temporal increase in the overall VOC level. This increase may occur during the cleaning process and thus it can enhance the probability of increased short-term exposure of the cleaners. However, the increased levels can also be present after the cleaning and result in an overall increased VOC level that can possibly affect the indoor air quality (IAQ) perceived by occupants. The variety and duration of the emissions depend inter alia on the use of fragrances and high boiling VOCs. Some building materials appear to increase their VOC emission through wet cleaning and thus may affect the IAQ. Particles and dirt contain a great variety of both volatile and non-volatile substances, including allergens. While the volatile fraction can consist of more than 200 different VOCs including formaldehyde, the non-volatile fraction can contain considerable amounts (> 0.5%) of fatty acid salts and tensides (e.g. linear alkyl benzene sulphonates). The level of these substances can be high immediately after the cleaning process, but few studies have been conducted concerning this problem. The substances partly originate from the use of cleaning agents. Both types are suspected to be airway irritants. Cleaning activities generate dust, mostly by resuspension, but other occupant activities may also resuspend dust over longer periods of time. Personal sampling of VOCs and airborne dust gives higher results than stationary sampling. International bodies have proposed air sampling strategies. A variety of field sampling techniques for VOC and surface particle sampling is listed.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. RRM WATER POLLUTION LC-50

Abstract  Densities and viscosities at T = 293.15, 298.15 and 303.15 K in the binary liquid mixtures of ethyl tert-butyl ether (ETBE) with propylene glycol monomethyl ether (PM), dipropylene glycol monomethyl ether (DPM) and tripropylene glycol monomethyl ether (TPM) have been measured over the entire mixture compositions. These data have been used to compute the excess molar volumes (V E), the excess energies of activation for viscous flow ΔG E, the deviations in the viscosity (Δη) from a mole fraction average and the Grunberg–Nissan interaction parameters (d 12). The values of V E, Δη, ΔG E and d 12 are negative over the entire range of composition for all the studied binary mixtures. The changes of V E, Δη, ΔG E and d 12 with variations in the composition and the chain-length of the alkyl groups in the alkoxypropanol molecules are discussed in terms of the intermolecular interactions.

Abstract  Consensus reports of the criteria Group of the Swedish National Institute of Occupational Health on 2-hexanone, some aliphatic monoketones, inorganic lead, dipropylene glycol monomethyl ether, chlorocresol, N-nitroso compounds, vinyltoluene, isophorone, monochloroacetic acid, nitrotoluenes, acrylamide, inorganic manganese, dinitrotoluenes, trinitrotoluene, dimethylethylamine, natural crystalline mineral fibres and talc. An appendix lists consensus reports appearing in previous volumes of Arbete och Hälsa

Abstract  Using data available in the Products Register at the Swedish National Chemical Inspectorate, an analysis was undertaken of the occurrence and turnover of glycol ethers in Sweden between 1986 and 1993. The most commonly used glycol ethers during 1991 and 1992 were propylene-glycol-monomethyl-ether (107982), ethylene-glycol-monobutyl-ether (111762), diethylene-glycol-monobutyl-ether (112345), and dipropylene-glycol-monomethyl-ether (20324327). Also used to a large extent were diethylene-glycol-monobutyl-ether-acetate (124174) (DEGBEA), diethylene-glycol-monoethyl-ether-acetate (112152), diethylene-glycol-monomethyl-ether (111773), and diethylene-glycol-monoethyl-ether (111900). The use of ethylene-glycol-monoethyl-ether (110805) and ethylene-glycol-monoethyl-ether-acetate (111159) decreased markedly from 1992 to 1993 while the use of all the other glycol ethers increased. The authors suggest that the marked increase in the use of ethylene-glycol-monomethyl-ether (109864) between 1992 and 1993 warrants further study.

Abstract  Isopropyl alcohol(IPA) is widely used as additive to enhance surface structure and reduce the reflectivity of silicon wafers in alkaline texturing process of mono-crystalline silicon solar cells currently. However, due to its low boiling point and high volatilization, some negative effects are brought into large scale production especially in stability, cost and environment. In this paper, Dipropylene glycol(DPG) which has relative high boiling point was tried to substitute IPA as texturing solution additive. The influences of concentration of DPG and NaOH on etching rate, surface morphology and reflectance spectrum were investigated. It is obviously observed that the silicon is prevented from etching reaction by the existence of DPG. The best weight reflectance of 13.6% is obtained on mono-crystalline silicon surface by an optimized solution of 1 wt% NaOH and 1 wt% DPG at 80 degrees C for 20 minutes. Finally, the influencing mechanism of DPG was also discussed in detail.

Abstract  The appropriate combination of viscosifier and coviscosifier is a very important factor in the control of the viscosity and adhesion properties of chemical decontamination gels. A chemical decontamination gel was prepared by adding gelling agents composed of a pyro Si viscosifier and PEG-based non-ionic coviscosifier (tripropylene glycol butyl ether and tripropylene glycol dodecyl ether) into a Ce(IV) solution stabilized in concentrated nitric acid. The decontamination and rheological behaviours, along with the drying behaviours of a chemical gel for SUS 304 metallic surfaces contaminated with Co and Cs radionuclides were investigated. A chemical gel containing a 0.5 wt % tripropylene glycol dodecyl ether coviscosifier was more effective in terms of the rheological and drying-detachment properties and the radionucleide decontamination effectiveness in particular, compared to tripropylene glycol butyl ether.

Abstract  Shrinkage behavior of the structural foam lightweight concrete with density of 1600 kg/m(3) was investigated. Owing to high drying shrinkage of the lightweight concrete, glycol compounds were used in the concrete mixture to study their effect on shrinkage behavior. Propylene glycol (PG), triethylene glycol (TEG) and dipropylene glycol tert-butyl ether (DPTE) were selected for testing of drying shrinkage of the lightweight concrete. Partial replacement of cement and sand with fly ash was also used to reduce the shrinkage. Results indicated that PG, TEG and DPTE were effective in reducing the shrinkage of lightweight concrete through reduction of surface tension of water. However, DPTE significantly reduced the surface tension and caused the foam instability and early stiffening of mixture. The partial replacement of cement and sand with fly ash could also reduce the shrinkage of the lightweight concrete. In this case, the compressive strength was also enhanced owing to the additional pozzolanic reaction. (C) 2010 Elsevier Ltd. All rights reserved.

Abstract  The oxygenated additives propylene glycol methyl ether (PGME), propylene glycol ethyl ether (PGEE), dipropylene glycol methyl ether (DPGME) were studied to determine their influence on both the base diesel fuel properties and the exhaust emissions from a diesel engine (CO, NOx, unburnt hydrocarbons and smoke). For diesel blends with low oxygen content (<= 4.0 wt.%), the addition of these compounds to base diesel fuel decreases aromatic content, kinematic viscosity, cold filter plugging point and Conradson carbon residue. Also, each compound modifies the distillation curve at temperatures below the corresponding oxygenated compound boiling point, the distillate percentage being increased. The blend cetane number depends on the type of propylene glycol ether added, its molecular weight, and the oxygen content of the fuel. The addition of PGME decreased slightly diesel fuel cetane number, while PGEE and DPGME increased it. Base diesel fuel-propylene glycol ether blends with 1.0 and 2.5 wt.% oxygen contents were used in order to determine the performance of the diesel engine and its emissions at both full and medium loads and different engine speeds (1000, 2500 and 4000 rpm). In general, at full load and in comparison with base diesel fuel, the blends show a slight reduction of oxygen-free specific fuel consumption. CO emissions are reduced appreciably for 2.5 wt.% of oxygen blends, mainly for PGEE and DPGME. NOx emissions are reduced slightly, but not the smoke. Unburnt hydrocarbon emissions decrease at 1000 and 2500 rpm, but not at 4000 rpm. At medium load, the effect of the additives is much less significant, due to the fact that the ratio oxygen from additive/oxygen from air is much lower. (C) 2013 Elsevier Ltd. All rights reserved.

Abstract  This loose-leaf collection was published under the auspices of the Toxic Substance Control Committee of the German Research Association. It contains basic information on approx. 300 substances (chemicals, gases, fumes, silica, asbestos, man-made mineral fibres, cutting fluids). Supplement 11 had one chapter devoted to passive smoking. Supplement 12 provides additional studies on: aluminium fumes and dust; acetaldehyde (update); ammonia (update); 1,4 and 2,4-butanesultone; 2-methyl-4-chloroaniline; dichloromethane (update); 3-3'-dimethoxybenzidine; 3-3'-dimethylbenzidine; dipropylene glycol monomethyl ether; ethyl acrylate; 2-nitro-p-phenylenediamine; o-toluidine; vinyl chloride; chlorodifluoromethane; 4-amino-2-nitrophenol; xylene.

Abstract  Porous and hollow particles are widely used in pharmaceuticals, as solid phases for chromatography, as catalyst supports, in bioanalytical assays and medical diagnostics, and in many other applications. By controlling size, shape, and chemistry, it is possible to tune the physical and chemical properties of the particles. In some applications of millimeter-scale hollow shells, such as in high energy density physics, controlling the shell thickness uniformity (concentricity) and roundness (sphericity) becomes particularly important. In this work, we demonstrate the feasibility of using electric field-driven droplet centering to form highly spherical and concentric polymerizable double emulsion (DE) droplets that can be subsequently photopolymerized into polymer shells. Specifically, when placed under the influence of an similar to 6 x 10(4) V-rms/m field at 20 MHz, DE droplets, consisting of silicone oil as the inner droplet and tripropylene glycol diacrylate with a photoinitiator in N,N-dimethylacetamide as the outer droplet, suspended in ambient silicone oil, were found to undergo electric field-driven centering into droplets with >= 98% sphericity and similar to 98% concentricity. The centered DE droplets were photopolymerized in the presence of the electric field. The high degrees of sphericity and concentricity were maintained in the polymerized particles. The poly(propylene glycol diacrylate) capsules are just within the sphericity requirements needed for inertial confinement fusion experiments. They were slightly outside the concentricity requirement. These results suggest that electric field-driven centering and polymerization of double emulsions could be very useful for synthesizing hollow polymer particles for applications in high energy density physics experiments and other applications of concentric polymer shells.

Abstract  Combustion behavior of various oxygenated fuels has been studied in a DAF heavy-duty (HD) direct-injection (DI) diesel engine. From these fuels, it is well-known that they lead to lower particle (PM) emissions; however, for a given fuel oxygen mass fraction, there are significant differences in PM reduction. Although this can be traced back to the specific molecular structure of the oxygenate in question, no consensus can be found in the literature as to the explanation hereof. In this study, the sooting tendency (smoke number) of three oxygenates [viz., tripropylene glycol methyl ether (TP), dibutyl maleate (DB), and cyclohexanone (X1)] was compared to that of commercial diesel fuel (EN590, D). The results suggest that the cetane number (CN) (i.e., fuel reactivity) may play an important role. More specifically, the low reactive oxygenate X1, with its cyclic carbon chain, was found to perform exceptionally well compared to the more reactive linear and branched oxygenates DB and TP, respectively. Cyclic oxygenates are abundant in nature. Cellulose, the most common organic compound on earth, is the best-known example. Although it is not trivial, liquid cyclic oxygenates can be made from lignocellulosic biomass. Particularly, the production of C6 oxygenates (e.g., guaiacol, cyclohexanone, phenol, etc.), which can be derived from lignin, is the subject of current investigation. Fuels produced from such biomass (e.g., plant waste or the nonedible part of plants) are referred to as second-generation biofuels and are expected to play a pivotal role in the near future.

Abstract  Detection thresholds are typically obtained by presenting a subject with serial dilutions of an odorant. Many factors, including the solvent used to dilute the odorant, can influence the measurement of detection thresholds. Differences have been reported in detection thresholds for phenyl ethyl alcohol (PEA) when different solvents are used. In this study we used gas chromatography (GC) to investigate further the effect of solvent on odor detection thresholds. We used a single ascending method and serial dilutions of PEA in four different solvents-liquid paraffin (LP), mineral oil (MO), propylene glycol (PG) and dipropylene glycol (DPG)-to determine the PEA thresholds for 31 adult subjects. For each solvent, we prepared eight serial log base 10 step dilutions (1 -8), with corresponding liquid PEA concentrations of 6.3 x 10(1)-6.3 x 10(-6) (% v/v). We found that the threshold concentrations for PEA in LP (step 6.5) and PEA in MO (step 5.5) were significantly lower (P < 0.05) than for PEA in PG (step 4.0) and DPG (step 4.0). We then used GC to measure both the liquid and gas PEA concentrations for the dilution steps prepared with LP and PG. Although there were large threshold differences in the liquid concentrations of PEA in LP and PG, the headspace gas concentrations of PEA were the same. These results demonstrate the importance of determining the gas concentration of odorant stimuli when performing odor threshold measurements, in particular when comparing odor detection thresholds obtained using different solvents.

Abstract  Anthramycin (ANT) is a member of the pyrolobenzodiazepine family and is a potent cytotoxic agent. Previously, we reported the topical delivery of ANT from a range of solvents that may also act as skin penetration enhancers (SPEs). The skin penetration and uptake was monitored for simple solutions of ANT in propylene glycol (PG), dipropylene glycol (DiPG), Transcutol P (TC), isopropyl myristate (IPM), propylene glycol monocaprylate (PGMC) and propylene glycol monolaurate (PGML). The amounts of PG, DiPG and TC that were taken up by, and that penetrated the skin were also measured, with a clear dependence of ANT penetration on the rate and extent of PG and TC permeation. The present work investigates ANT skin delivery from a range of binary and ternary systems to determine any potential improvement in skin uptake compared with earlier results for the neat solvents. Following miscibility and stability studies a total of eight formulations were taken forward for evaluation in human skin in vitro. Binary systems of PG and water did not result in any skin permeation of ANT. Combining PG with either PGMC or PGML did promote skin penetration of ANT but no significant improvement was evident compared with PG alone. More complex ternary systems based on PG, DiPG, PGMC, PGML and water also did not show significant improvements on ANT permeation, compared with single solvents. Total skin penetration and retention of ANT ranged from 1 to 6% across all formulations studied. Where ANT was delivered to the receptor phase there were also high amounts of PG permeation with >50% and ~35% PG present for the binary systems and ternary vehicles, respectively. These findings along with our previous paper confirm PG as a suitable solvent / SPE for ANT either alone or in combination with PGML or PGMC. The results also underline the necessity for empirical testing to determine whether or not a vehicle is acting as a SPE for a specific active in a topical formulation.

Abstract  In this study, we examined the influence of the dispersion solvent in three dipropylene-glycol/water (DPG/water) mixtures, with DPG contents of 0, 50, and 100 wt%, on ionomer morphology and distribution, using dynamic light scattering (DLS) and molecular-dynamics (MD) simulation techniques. The DLS results reveal that Nafion-ionomer aggregation increases with decreasing DPG content of the solvent. Increasing the proportion of water in the solvent also led to a gradual decrease in the radius of gyration (Rg) of the Nafion ionomer due to its strong backbone hydrophobicity. Correspondingly, MD simulations predict Nafion-ionomer solvation energies of -147 ± 9 kcal/mol in water, -216 ± 21 kcal/mol in the DPG/water mixture, and -444 ± 9 kcal/mol in DPG. These results suggest that higher water contents in mixed DPG/water solvents result in increased Nafion-ionomer aggregation and the subsequent deterioration of its uniform dispersion in the solvent. Moreover, radial distribution functions (RDFs) reveal that the (-CF2CF2-) backbones of the Nafion ionomer are primarily enclosed by DPG molecules, whereas the sulfonate groups (SO3-) of its side chains mostly interact with water molecules.