Polystyrene Mark-Houwink parameters

Table I indicates good agreement between the molecular weight distribution statistics obtained by coupled GPC/Viscometer method and the nominal values for t BS 706. The discrepancy between the Mark-Houwink parameters obtained here and the reported values for polystyrene standard ( ) in THF at 25°C (i.e., a = 0,706 and k = 1.60 x 10 ) may in part be due to the uncertainty involved in the determination of the dead volume between DRI and viscometer detectors. Our simulation studies over a range of dead volume values (0 to 120u)l) showed that a and k are quite sensitive to the dead volume between the detectors. Larger dead volume results in smaller o and larger k values. This is a direct result of a clockwise rotation of log [q] vs. log M(v) curve (Figure 12) which occurs when the dead volume correction is applied in quantitative analysis. The effect on the molecular weight statistics, however, appeared to...

The use of a continuous GPC viscosity detector in conjunction with a DRI detector permits the quantitative determination of absolute molecular weight distribution in polymers. Furthermore, from this combination one can obtain Mark-Houwink parameters and the bulk intrinsic viscosity of a given polymer with a GPC calibration curve based only on polystyrene standards. Coupling these two detectors with ultraviolet and infrared detectors then will permit the concurrent determination of polymer composition as a function of molecular weight and... 

Dead Volume. The dead volume difference between the viscometer and DRI must be accounted for. Otherwise systematic errors in Mark-Houwink parameters K and u can occur. In the previous paper (16), a method developed by Lesec and co-workers (38) based on injecting a known amount of a very high molecular weight polystyrene standard onto low porosity columns was used. From the viscometer and DRI chromatograms, the apparent intrinsic viscosity [h] was plotted against retention volume V. A series of [n] vs. V plots are then constructed assuming a range of dead volume, AV. 

Polystyrene. Table 3 shows the results obtained for three broad MWD polystyrene samples. The agreement for M and M values obtained from SEC/Viscometry analysis and the nominaY values supplied by the vendors is excellent. In addition the Mark-Houwink parameters, K and a values also are in excellent agreement with each other as well as with literature values.(28,39) This shows the consistency of the analysis method and the technique for determining the dead volume between detectors. The lower M value for the NBS 706 sample is due to the low molecular weight tail associated with the sample. 

Route 1 (a) Using the Mark-Houwink parameters of the PMMA test polymer in tetrahydrofuran, cthfia and thf A> construct the PMMA molecular weight calibration curve in tetrahydrofuran from the polystyrene HDV calibration curve by the use of Equation 2 where x is PMMA... 

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