Polystyrenes thermal field-flow fractionation

Janca, J. Martin, M. Influence of operational parameters on retention of ultra-high molecular weight polystyrenes in thermal field-flow fractionation. Chromatographia 1992,34,125. Semyonov, S.N. Kuznetsov, A. A. Zolotaryov, P.P. Theoretical examination of focusing field-flow ftactionation. J. Chromatogr. 1986, 364, 389. 

Brimhall, S.L. Myers, M.N. Caldwell, K.D. Giddings, J.C. Study of temperature dependence of thermal diffusion in polystyrene/ethylbenzene by thermal field-flow fractionation. J. Polym. Sci., Polym. Phys. Ed., 1985, 23, 2443. 

Fig. 1 Plots of log XAT vs. log TJ 298 for polystyrene in tetrahydrofuran. The data were gathered using a variety of different ThFFF channels. Values of AT ranged from 30 to 70 K. Source Reproduced with permission from Thermal field-flow fractionation universal calibration Extension for consideration of variation of cold wall temperature, in Anal. Chem. ...

Field flow techniques have been reviewed in a number of articles [148-150]. Sedimentation field flow fractionation has found use in the separation of PVC [151, 152], polystyrene [151-153], poly(methyl methacrylate) [153, 154], poly (vinyl toluene) [155] and poly(glycidyl methacrylate) latexes [156] to produce particle-size distributions and particle densities. It has also been applied in polymer-aggregation studies [157], pigment [157] quality control and in the separation of silica particles [158] and its performance has been compared with that of ultracentrifugation [159]. Thermal field flow fractionation has been used successfully in the characterisation of ultra-high-molecular-weight polystyrenes [160, 161], poly(methyl methacrylate), polyisoprene, polysulphane, polycarbonate, nitrocellulose, polybutadiene and polyolefins [162]. In the difficult area of water-soluble polymers, poly(ethylene glycol), poly(ethylene oxide), poly(vinyl pyrrolidone) and poly(styrene sulphonate) have been analysed [163, 164]. In addition, compositional separations have been achieved for polystyrene-poly(methyl methacrylate) mixes [165] and comparisons between TFFF and SEC have been made [166]. 

Flow field - flow fractionation has been used" to fractionate polystyrene and Kirkland and Rementer" used thermal field flow fractionation using Mark Houweq constants to determine the molecular weight distribution of polystyrene and poly methylstyrene. 

Flow FFF is perhaps most promising in the area of water-soluble polymers. These polymers, which as a class are very difficult or impossible to separate by thermal FFF, can be fractionated according to diffusion coefficient or Stokes radius (which translate to molecular mass) in a flow FFF system using a water-compatible membrane such as cellulose acetate. Such a fractionation is shown in Figure 8.15, illustrating the programmed field separation of three sulphonated polystyrene components in a 510-//m-thick channel. The fact that the time of separation is somewhat longer than desired can be related to the excessive thickness of the channel, ten times thicker than the thinnest thermal FFF channel utilized. Recently we have been able to work successfully with a... 

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