Tetrahydrofuran , polystyrene

Bernardin, F. E. Ill Geveke, D. J. Danner, R. P., "Ternary Phase Equilibria of Tetrahydrofuran-Polystyrene- Polytetrahydrofuran," Department of Chem. Eng. The Pennsylvania State University University Park, PA, (1991). 

The application of universal calibration requires a primary column calibration with elution of narrow MWD standards. For SEC in tetrahydrofuran, polystyrene (PS) standards are generally used. Intrinsic viscosities of the standards are either known or calculated from the proper Mark-Houwink equation, so that the plot of log[7j]psMps values versus retention vol-... 

GE2 Geveke, D.J., Bemardin, F.E., aM Darmer, R.P., Ternary phase equilibria of tetrahydrofuran-polystyrene-polytetrahydrofuran, J. Appl. Polym. ScL, 50, 251, 1993. 

Figure 5.1 (a) Self-diffusion of tetrahydrofuran, and (b) tracer diffusion of hexafluorobenzene through tetrahydrofuran polystyrene for polystyrene molecular weights (O) 10, (0) 37.4, ( ) 179, (A) 498, and (V) 1050 kDa, showing Ds does not depend on polymer molecular weight. Original measurements from von Meerwall, et... 

The first living polymer studied in detail was polystyrene polymerized with sodium naphthalenide in tetrahydrofuran at low temperatures ... 

FIGURE 4.38 Calibration curves for TSK-GEL Hxl columns with polyst/rene standards. Column TSK-GEL Hxl series, two 7.8 mm x 30 cm columns in series. Sample Polystyrene standards. Elution Tetrahydrofuran. Flow rate 1.0 ml/min. Detection Rl. 

The ISO method prescribes polystyrene standards with tetrahydrofuran as the eluent, but this equation can also be used with other narrow distribution standards, provided the same elution solvent and the same standards are used for a comparison. Further, the ISO method requires the result to be greater than 6 for one decade of the molar mass. Because calibration curves are usually not linear, this decade should lie nearly symmetrically around the peak maxima of the samples in question. The required value of 6 is easy to fulfill, as results of 10 or more are usual with modern columns. If so-named linear or mixed... 

Addition of styrene to a green solution of naphthalene" Na+ in tetrahydrofuran leads to an instantaneous change of color from green to red. Styrene polymerizes rapidly and quantitatively within a few seconds, and when the reaction is completed, addition of water converts the red solution of polystyryl carbanions into colorless solution of polystyrene. After precipitation of the polymer it was shown spectroscopically25 that the residual solution contains an amount of naphthalene equal to that used in the preparation of the initiating catalyst. This observation confirms the proposed mechanism of initiation of the polymerization. 

In summary, silica gel can be an excellent stationary phase for use in exclusion chromatography in the separation of high molecular weight, weakly polar or polarizable polymers. It cannot be used for separating mixtures that require an aqueous mobile phase or operate at a pH outside the range of 4-8. Examples of the type of materials that can be separated by exclusion chromatography using silica gel are the polystyrenes, polynuclear aromatics, polysiloxanes and similar polymeric mixtures that are soluble and stable in solvents such as tetrahydrofuran. 

Gel Permeation Chromatography. The instrument used for GPC analysis was a Waters Associates Model ALC - 201 gel permeation chromatograph equipped with a R401 differential refractometer. For population density determination, polystyrene powder was dissolved in tetrahydrofuran (THF), 75 mg of polystyrene to SO ml THF. Three y -styragel columns of 10, 10, 10 A were used. Effluent flow rate was set at 2.2 ml/min. Total cumulative molar concentration and population density distribution of polymeric species were obtained from the observed chromatogram using the computer program developed by Timm and Rachow (16). 

Linear non-cross-linked polystyrene has been used for organic synthesis since it is readily soluble in common organic solvents (i.e., dichloromethane, chloroform, tetrahydrofuran, toluene, ethyl acetate, and pyridine) but precipitates upon addition of water or methanol [123-126]. However, no examples of the use of this polymer in conjunction with microwave chemistry have been reported. 

Gel permeation chromatography was performed in tetrahydrofuran using a Waters pump system and a Model 410 differential refractive index detector for the eluant. Five Ultrastyragel columns with nominal porosities ranging from 500 to 105 angstroms were used for all the samples and the polystyrene standards. 

Figure 2 Chromatogram from conventional SEC column compared to high-speed SEC column tested on an identical instrument with polystyrene standards in tetrahydrofuran (THF). (See Color Plate Section at the end of this book.)...

On each of the curves, the points at lowest X represent swelling in cyclohexane, the next in tetrahydrofuran and the last in benzene. In all cases, the samples were swollen in the pure solvent. The curves are reproduced from Figure 13 of Reference 19. The networks were made from anionically polymerized polyr-styrene using a bifunctional initiator crosslinked subsequently by divinyl benzene. The curves correspond to different ratios of divinyl benzene (DVB) per polystyrene living end (LE),... 

In a recent study, another method for microwave-assisted heterocycle synthesis leading to a small set of imidazole derivatives has been reported [54], These pharmaceutically important scaffolds were synthesized utilizing polymer-bound 3-N,N-(dimethylamino)isocyanoacrylate. This polymer support was easily prepared by treatment of [4-(bromomethyl)phenoxy]methyl polystyrene with a twofold excess of the appropriate isocyanoacrylate potassium salt in N,N-dimethylformamide (Scheme 7.37). The obtained intermediate was subsequently treated with N,N-di-methylformamide diethyl acetal (DMFDEA) in a mixture of tetrahydrofuran and ethanol to generate the desired polymer-bound substrate. 

Figure 5.17 Stability of optical encoding towards oligonucleotide reagents. Organosilica microspheres covalently labelled with ATTO 550 dye are stable towards each of the reagents used in phosphoramidite oligonucleotide synthesis. In contrast, optically encoded polystyrene-divinylbenzene (DVB) beads are unstable in most steps, in particular those involving dichloromethane and tetrahydrofuran. (Reproduced from ref. 28, with permission.)...

As the final products—polystyrene-h-polyivinylperfluorooctanoic ester)— form micelles in tetrahydrofuran (THF) as well as in DMF, there are not direct GPC data to characterize molecular parameter. For this reason, we employed esterification of the hydroxylated block copolymers with benzoylchloride as a model reaction to obtain a comparable product with molecular solubility that can easily be characterized by DMF-GPC. The GPC data from PSB-II—our largest and therefore most sensitive block copolymer—are summarized in Table 10.2. Results for all the other polymers are similar. 

Fig A typical gel permeation chromatogram polystyrene in tetrahydrofuran, which Ms/Mw = 2.9. 

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