Water activity in poly(ethylene glycol) aqueous solutions

Ninni, Luciana; Camargo, M. S.; Meirelles, Antônio J. A.

doi:10.1016/s0040-6031(98)00638-8

Cited by 133 publications

(123 citation statements)

References 12 publications

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“…Because of the dry environment of the EDB in these experiments (< 5 % RH), effectively all of the water was assumed to evaporate out of the particles after injection on the timescale of seconds, leaving behind a PEG particle with a starting mass proportional to the PEG weight fraction of the prepared solution. Running the evaporation model (described below) with a mole fraction of water of 0.05 (corresponding to ∼ 5 % RH, Ninni et al, 1999) confirmed that the presence of water under these dry conditions was predicted to have a negligible effect on the evaporation rate and hence could be safely disregarded.…”

Section: Sample Preparationmentioning

confidence: 93%

“…was measured to be 12 %. A fixed water activity of 0.12 was estimated to correspond to a mole fraction of water of 0.18 in the particle, from a previous experimental study of water-PEG-200 mixtures (Ninni et al, 1999), and this fixed mole fraction of water was included in the model in addition to the PEG-4 and PEG-6. The model was run with the mean experimentally measured temperature in the EDB, 291.06 K.…”

Section: Peg-mentioning

confidence: 99%

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Electrodynamic balance–mass spectrometry of single particles as a new platform for atmospheric chemistry research

Birdsall

Krieger²,

Keutsch

2018

Atmos. Meas. Tech.

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Abstract. New analytical techniques are needed to improve our understanding of the intertwined physical and chemical processes that affect the composition of aerosol particles in the Earth's atmosphere, such as gas-particle partitioning and homogenous or heterogeneous chemistry, and their ultimate relation to air quality and climate. We describe a new laboratory setup that couples an electrodynamic balance (EDB) to a mass spectrometer (MS). The EDB stores a single laboratory-generated particle in an electric field under atmospheric conditions for an arbitrarily long length of time. The particle is then transferred via gas flow to an ionization region that vaporizes and ionizes the analyte molecules before MS measurement. We demonstrate the feasibility of the technique by tracking evaporation of polyethylene glycol molecules and finding agreement with a kinetic model. Fitting data to the kinetic model also allows determination of vapor pressures to within a factor of 2. This EDB-MS system can be used to study fundamental chemical and physical processes involving particles that are difficult to isolate and study with other techniques. The results of such measurements can be used to improve our understanding of atmospheric particles.

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Section: Sample Preparationmentioning

confidence: 93%

Section: Peg-mentioning

confidence: 99%

Electrodynamic balance–mass spectrometry of single particles as a new platform for atmospheric chemistry research

Birdsall

Krieger²,

Keutsch

2018

Atmos. Meas. Tech.

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“…It is well known that the water activity and phase equilibria of PEG oligomers and polymers in aqueous solutions are rather poorly described (e.g., Ninni et al, 1999) when the standard set of functional groups is used in the UNIversal quasi-chemical Functional group Activity Coefficient model (UNIFAC; Fredenslund et al, 1975;Hansen et al, 1991) and hence also in AIOMFAC, which includes a modified UNIFAC model. In order to provide an improved model representation of aqueous PEGs (of various polymer chain lengths) and of the ternary water + PEG + AS phase diagrams, a special oxyethylene group (-CH 2 -O-CH 2 -; the repetitive monomer unit in PEG) was introduced in a recently developed PEG-specific AIOMFAC parameterization.…”

Section: Thermodynamic Modelingmentioning

confidence: 99%

“…A(a w ) and B(a w ) can be estimated based on parameterizations for a chemically similar reference compound, here sucrose (Zobrist et al, 2011), relying on the assumptions that (1) D H 2 O of PEG and sucrose behave similarly approaching T g (i.e., B sucrose ≈ B PEG ), (2) D H 2 O is similar for PEG and sucrose at the high temperature limit (i.e., A sucrose ≈ A PEG ), and (3) both systems exhibit a similar ratio of T 0 to T g (i.e., T 0,sucrose /T 0,PEG ≈ T g,sucrose /T g,PEG ) (Berkemeier et al, 2014). Values of a w and T g for PEG200 and PEG10000 were taken from the literature (Ninni et al, 1999;Pielichowsk and Flejtuch, 2002;Dow, 2011). Calculated values of D H 2 O were then used to estimate the e-folding time of bulk diffusion (i.e., the time required for the concentration of water in the core of a particle exposed to a given RH to be within a factor of 1/e of thermodynamic equilibrium) for 250 nm particles comprised of both PEG200 and PEG10000:…”

Section: Estimation Of Water Diffusivity and Mixing Timescalementioning

confidence: 99%

Discontinuities in hygroscopic growth below and above water saturation for laboratory surrogates of oligomers in organic atmospheric aerosols

et al. 2016

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Abstract. Discontinuities in apparent hygroscopicity below and above water saturation have been observed for organic and mixed organic-inorganic aerosol particles in both laboratory studies and in the ambient atmosphere. However, uncertainty remains regarding the factors that contribute to observations of low hygroscopic growth below water saturation but enhanced cloud condensation nuclei (CCN) activity for a given aerosol population. Utilizing laboratory surrogates for oligomers in atmospheric aerosols, we explore the extent to which such discontinuities are influenced by organic component molecular mass and viscosity, non-ideal thermodynamic interactions between aerosol components, and the combination of these factors. Measurements of hygroscopic growth under subsaturated conditions and the CCN activity of aerosols comprised of polyethylene glycol (PEG) with average molecular masses ranging from 200 to 10 000 g mol −1 and mixtures of PEG with ammonium sulfate (AS) were conducted. Experimental results are compared to calculations of hygroscopic growth at thermodynamic equilibrium conducted with the Aerosol Inorganic Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) model, and the potential influence of kinetic limitations on observed water uptake was further explored through estimations of water diffusivity in the PEG oligomers. Particle-phase behavior, including the prevalence of liquid-liquid phase separation (LLPS), was also modeled with AIOMFAC. Under subsaturated relative humidity (RH) conditions, we observed little variability in hygroscopic growth across PEG systems with different molecular masses; however, an increase in CCN activity with increasing PEG molecular mass was observed. This effect is most pronounced for PEG-AS mixtures, and, in fact, an enhancement in CCN activity was observed for the PEG10000-AS mixture as compared to pure AS, as evidenced by a 15 % reduction in critical activation diameter at a supersaturation of 0.8 %. We also observed a marked increase in apparent hygroscopicity for mixtures of higher molecular mass PEG and AS under supersaturated conditions as compared to subsaturated hygroscopic growth. AIOMFAC-based predictions and estimations of water diffusivity in PEG suggest that such discontinuities in apparent hygroscopicity above and below water saturation can be attributed, at least in part, to differences in the sensitivity of water uptake behavior to surface tension effects. There is no evidence that kinetic limitations to water uptake due to the presence of viscous aerosol components influenced hygroscopic growth. For the systems that display an enhancement in apparent hygroscopicity above water saturation, LLPS is predicted to persist to high RH. This indicates a miscibilityPublished by Copernicus Publications on behalf of the European Geosciences Union. 12768 N. Hodas et al.: Discontinuities in the hygroscopicity of oligomers gap and is likely to influence bulk-to-surface partitioning of PEG at high RH, impacting droplet surface tension and CCN activity....

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“…One way to overcome this limitation is to define parameters that are specific for certain compound classes. Such parameterizations have been proposed by Peng et al (2001) for dicarboxylic and hydroxyl-carboxylic acids and by Ninni et al (1999) for poly(ethylene glycol). Ming and Russell (2002) proposed modified parameterizations for long-chain monofunctional compounds, monosaccharides, hydroxyl-acids and diacids.…”

Section: New Unifac Parameterizationmentioning

confidence: 99%

Water activity in polyol/water systems: new UNIFAC parameterization

Marcolli¹,

Peter²

2005

Atmos. Chem. Phys.

106

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Abstract. Water activities of a series of polyol/water systems were measured with an AquaLab dew point water activity meter at 298 K. The investigated polyols with carbon numbers from n=2-7 are all in liquid state at room temperature and miscible at any molar ratio with water. In aqueous solutions with the same molar concentration, the diols with lower molecular weight lead to lower water activities than those with higher molecular weights. For diols with four or more carbon atoms, the hydrophilicity shows considerable differences between isomers: The 1,2-isomers -consisting of a hydrophilic and a hydrophobic part -bind less strongly to water than isomers with a more balanced distribution of the hydroxyl groups. The experimental water activities were compared with the predictions of the group contribution method UNIFAC: the model predictions overestimate the water activity of water/polyol systems of substances with two or more hydroxyl groups and can not describe the decreased binding to water of isomers with hydrophobic tails. To account for the differences between isomers, a modified UNIFAC parameterization was developed, that allows to discriminate between three types of alkyl groups depending on their position in the molecule. These new group interaction parameters were calculated using water activities of alcohol/water mixtures. This leads to a distinctly improved agreement of model predictions with experimental results while largely keeping the simplicity of the functional group approach.

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Water activity in poly(ethylene glycol) aqueous solutions

Cited by 133 publications

References 12 publications

Electrodynamic balance–mass spectrometry of single particles as a new platform for atmospheric chemistry research

Electrodynamic balance–mass spectrometry of single particles as a new platform for atmospheric chemistry research

Discontinuities in hygroscopic growth below and above water saturation for laboratory surrogates of oligomers in organic atmospheric aerosols

Water activity in polyol/water systems: new UNIFAC parameterization

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