In the present study, the mutual diffusivity D11 in binary mixtures of water with technical polydisperse poly(ethylene) glycol (PEG) blends with molar masses of (1000, 4000, or 6000) g⋅mol−1 as well as with a purified monodisperse PEG homolog with a polymerization number of 21 and a molar mass of 943 g⋅mol−1 was investigated by heterodyne dynamic light scattering (DLS) as a function of temperature and/or PEG concentration. The measured D11 for technical PEG 1000 and pure PEG 943 match within the experimental uncertainties and agree well with the available literature data. D11 decreases with increasing molar mass of the PEGs at constant temperature and weight fraction. For the technical PEG 4000, it could be shown that D11 increases with increasing temperature and exhibits a nonlinear concentration dependence. This study demonstrates that heterodyne DLS can be applied for the reliable determination of D11 of aqueous solutions of PEGs over a broad range of PEG weight fractions from 0.01 up to the solubility limit with an average expanded uncertainty (k = 2) of 5.5 %. Moreover, the results show that monodisperse PEGs are suitable model systems for studying the diffusion behavior of bimodal and also multimodal particulate systems.
The separation of polyethylene glycols (PEGs) into single homologs by reversed-phase chromatography is investigated experimentally and theoretically. The used core–shell column is shown to achieve the baseline separation of PEG homologs up to molar weights of at least 5000 g/mol. A detailed study is performed elucidating the role of the operating conditions, including the temperature, eluent composition, and degree of polymerization of the polymer. Applying Martin’s rule yields a simple model for retention times that holds for a wide range of conditions. In combination with relations for column efficiency, the role of the operating conditions is discussed, and separations are predicted for analytical-scale chromatography. Finally, the approach is included in an efficient process model based on discrete convolution, which is demonstrated to predict with high accuracy also advanced operating modes with arbitrary injection profiles.
In the present study, the mutual diffusivity D11 in binary mixtures of water with technical polydisperse poly(ethylene) glycol (PEG) blends with molar masses of (1000, 4000, or 6000) g⋅mol−1 as well as with a purified monodisperse PEG homolog with a polymerization number of 21 and a molar mass of 943 g⋅mol−1 was investigated by heterodyne dynamic light scattering (DLS) as a function of temperature and/or PEG concentration. The measured D11 for technical PEG 1000 and pure PEG 943 match within the experimental uncertainties and agree well with the available literature data. D11 decreases with increasing molar mass of the PEGs at constant temperature and weight fraction. For the technical PEG 4000, it could be shown that D11 increases with increasing temperature and exhibits a non-linear concentration dependence. This study demonstrates that heterodyne DLS can be applied for the reliable determination of D11 of aqueous solutions of PEGs over a broad range of PEG weight fractions from 0.01 up to the solubility limit with an average expanded uncertainty (k = 2) of 5.5%. Moreover, the results show that monodisperse PEGs are suitable model systems for studying the diffusion behavior of bimodal and also multimodal particulate systems.
The isolation of single homologs of polyethylene glycol by preparative reversed-phase chromatography is investigated. A thermodynamic model developed accurately previously describes the retention times of individual homologs as function of their size, temperature, and mobile phase composition under linear, diluted conditions. The model is extended to predict limiting retention times for linear gradient operation in preparative applications. Isocratic and gradient-based separations are studied under strongly overloaded conditions. Baseline separation of homologs up to 3000 g/mol is demonstrated. Quantitative production of pure single homologs up to molar weights of 1000 g/mol was performed using an automated setup.
Separation of polyethylene glycols (PEGs) into single homologs by reversed-phase chromatography is investigated experimentally and theoretically. The used core-shell column is shown to achieve baseline separation of PEG homologs up to molar weights of at least 5000 g/mol. A detailed study is performed elucidating the role of the operating conditions temperature, eluent composition, and degree of polymerization of the polymer. Applying Martin's rule yields a simple model for retention times that holds for a wide range of conditions. In combination with relations for column efficiency, the role of the operating conditions is discussed and separations are predicted for analytical-scale chromatography. Finally, the approach is included in an efficient process model based on discrete convolution, which is demonstrated to predict with high accuracy also advanced operating modes with arbitrary injection profiles.
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