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Synthesis and Functionalization of Magnetic Particles
Published in Jeffrey N. Anker, O. Thompson Mefford, Biomedical Applications of Magnetic Particles, 2020
Erika C. Vreeland, Dale L. Huber
Size exclusion chromatography (SEC), also known as gel permeation chromatography (GPC), is a liquid chromatographic technique typically used to separate macromolecules in solution. SEC columns are packed with porous media (either polymer or silica based) that separate molecules according to their hydrodynamic volume in solution. Large molecules explore less of the pore volume of the stationary phase, allowing them to elute from the column faster than smaller molecules. In a similar manner, a suspension of nanoparticles can be purified from excess reagents by passing the mixture through an SEC column and collecting the pure nanoparticle eluent (Davis et al. 2014). Depending on the surface functionalization of the nanoparticles, a broad selection of aqueous and organic mobile phases can be used with either polymer- or silica-based stationary phases, making this a flexible purification technique.
Characterization Techniques for Polymers and Polymer Nanocomposites
Published in Alexander V. Vakhrushev, A. K. Haghi, Composite Materials Engineering, 2019
Chromatographic analysis is an important tool wherein the sample to be investigated is made into a solution with a right kind of solvents and by developing a right method sample analytes are analyzed say in HPLC. These techniques help analyze thermally labile, molecular, polar, or nonpolar materials with a great degree of accuracy and reproducibility. There has been an evolution in HPLC with the development of advanced techniques like UPLC, UFLC, etc., which further improve sensitivity, selectivity, rapidity, etc., in the analysis. GC requires samples to be analyzed, which are necessarily volatile and thermally stable, and by developing a right method based on the boiling range of the components, analysis can be done accurately and reproducibly both qualitative and quantitative. IC is also a type of LC wherein the ion-selective membranes find use in analyzing ionic species in the sample under investigation. Hyphenated techniques like LC-MS or GC-MS etc. are required to be used when LC or GC in isolation is unable to qualitatively and or quantitatively analyze the analytes in question. GPC helps in measuring molecular weight and its distribution profile as polydispersity index from the data generated for the polymers. There has been a lot of evolution in the GPC systems which are provided with detectors like DRI, UV-Vis, FTIR, LALLS, etc. which are used depending upon the requirements of the sample in the question of the polymer.
Measurement of Molecular Weight and Its Distribution
Published in Anil Kumar, Rakesh K. Gupta, Fundamentals of Polymer Engineering, 2018
The simplest conceptual method of determining the molecular weight distribution of a polymer sample is to separate the polydisperse sample into its constituent fractions and then measure the molecular weight of each fraction using any of the techniques discussed so far. This is exactly what used to be done until the commercialization in the mid-1960s of the procedure known as gel permeation chromatography (GPC), or size-exclusion chromatography. With the old method, a polymer in solution was fractionated either by the sequential addition of nonsolvents or by the progressive lowering of temperature (see Chapter 9 for the theory of polymer–polymer phase equilibrium). However, this was a very tedious and time-consuming process that was obviously ill-suited to routine laboratory procedures. The new method of GPC uses the fact that large polymer molecules are excluded from the small channels in a porous gel, with the result that different molecular weight fractions travel down a column packed with the porous medium at different rates, leading to separation based on size.
Improvements on the use of GPC to measure large-size microstructures in aged asphalt binders
Published in International Journal of Pavement Engineering, 2022
Gel permeation chromatography (GPC), or generally called size exclusion chromatography (SEC), is one of the most commonly used liquid chromatography (LC) method. Known as ‘molecule sieve’, GPC separates molecules in organic solutions according to their size and provides information on molar mass distribution (MMD or MWD). Since 1960s, GPC has been used in characterising the molecules of asphalt binders (e.g. Altgelt 1965, Dickie and Yen 1967). Information obtained from GPC is used to calculate the weight-average molecular weight Mw or the number-average molecular weight Mn, which is further correlated to the rheological properties such as the complex shear modulus or phase angle in the above-mentioned Christensen-Anderson model (Christensen and Anderson 1992). A more commonly used approach, however, is to divide a GPC chromatogram into several parts and use the portions corresponding large molecules as a performance-related indicator. For example, Jennings et al. (1980) and Kim et al. (1995) proposes to divide the GPC chromatogram into 13 slices and use the area of the first five slices to represent the large molecular size (LMS), the area of the next four slices for the middle molecular size (MMS), and the area of the last four slices for the small molecular size (SMS).
Determination of the optimum polystyrene parameters using asphalt binder modified with poly(styrene-acrylated epoxidised soybean oil) through response surface modelling
Published in Road Materials and Pavement Design, 2019
Conglin Chen, Joseph H. Podolsky, R. Christopher Williams, Eric W. Cochran
H-NMR spectroscopic analysis on the produced PS-PAESO polymers was performed on by using a 600 MHz Bruker Avance III spectrometer. The actual effective PS contents can be obtained from the H-NMR spectrum graph. A HT-GPC was used to measure molecular weight and molecular weight distribution of the PS-PAESO polymer. The results from HT-GPC provide important information for predicting the processability, material properties, and quantitative analysis of a polymer. The compatibility between polymer and asphalt binder and dispersity of the polymer within asphalt binder were examined using a fluorescence microscope with high-intensity light to illuminate specimens on a sample glass slide to produce magnified and lightened images. The specific results can be found in previously published research (Chen et al., 2017).