Size exclusion data, polystyrene

Novolac molecular weights were measured in THF at 35°C by high pressure size exclusion chromatography using a Waters Model 510 pump (flow rate=1.0 ml/min), 401 differential viscometer detector and a set of Dupont PSM 60 silanized columns. A universal calibration curve was obtained with a kit of 10 narrow molecular weight distribution, linear polystyrene standards from Toya Soda Company. Data acquisition and analysis were performed on an AT T 6312 computer using ASYST Unical 3.02 software supplied with the Viscotek instrument. 

Figure 26-15 Larger CdSe quantum dots are eluted before smaller quantum dots by 0.1 M trioctylphosphine in toluene at 1.0 mL/min in size exclusion chromatography on a 7.5 x 300 mm cross-linked polystyrene column of 100-nm pore size Polymer Labs PLgel 5 (im. Triangles are CdSe and squares are polystyrene calibration standards. The size of the CdSe core was measured with a transmission electron microscope and the length of 1-dodecanethiol endcaps (0.123 nm) was added to the radius. [Data from K. M. Krueger. A. M. Al-Somall, J. C. Falkner, and V. L. Colvin, "Characterization of Nanocrystalline CdSe by Size Exclusion Chromatography," Anal. Chem. 2005, 77,3511.]...

Universal calibration curve for size exclusion chromatography. Data points are polybutadienes in tetrahydrofuran at 25 °C in crosslinked polystyrene columns. There is a reasonably linear region of the calibration curve spanning the data (solid line) but the linear region has its limits (dotted curves). 

SEC is presently the most important method for separation and moleeular characterization of synthetic polymers. The method enjoys enormous popularity and most institutions involved in research, production, testing and apphea-tion of synthetie polymers are equipped at least with a simple SEC instrument. Size exclusion chromatograms are often directly transformed into the molar mass dispersity functions (compare section 11.3.3, Molar Mass Dispersity). Often, the molar mass data presented are not absolute, beeause polystyrene or other polymer standards distinct from polymer under study have been employed for the column calibration (see sections 11.6.3 and 11.7.3.1). Still, the data equivalent to the polymer applied to the column cahbration, more or less precisely represent the tendencies of molar mass evolution in the course of building-up or decomposition polyreactions. 

Cycloaliphatic resins were prepared by complete hydrogenation of selected aromatic resins. Molecular weight data were obtained by size exclusion chromatography, using a Styragel column set with THF as the mobile phase. Calculations were based on a polystyrene calibration. Glass transition temperatures were obtained by differential scanning calorimetry from the first break on the second heat. 

Polymers lb and 2b were obtained as colorless materials in yields exceeding 95%. Size exclusion chromatography in THF versus polystyrene standard gave the following molecular weight values which are representative for unfractionated samples, lb Mn = 9,700 (Pn = 22), Mw = 15,500 (Pw = 35), D = 1.6 2b Mn = 12,000 (Pn = 22), Mw = 20,000 (Pw = 36), D = 1.7. TTie polymers were characterized further by and NMR spectroscopy and elemental analysis. All data are in agreement with the proposed structures. (For a recent discussion of possible side reactions of the Suzu cross-coupling see reference 12.)... 

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