Secondary molecular weight calibration curve

Using the intrinsic viscosity data and the universal calibration curve( ) a secondary molecular weight calibration curve can be constructed for the polymer of interest as shown by the following equation ... 

This "secondary" molecular weight calibration curve was fit to a polynomial over the retention volume range of the sample. Then the molecular weight distribution statistics are calculated from this "secondary" calibration curve and the DRI trace of the sample under... 

Figure 10. "Secondary" Molecular Weight Calibration Curve for a PMMA Sample (Eastman 6041).

Figure 1. Illustrative method for constructing a secondary molecular weight calibration curve from an HDV calibration curve and intrinsic viscosity values of GPC polymer fractions...

Using the PMMA direct molecular weight calibration curve shown in Figure 4 and the Mark-Houwink parameters for PMMA in TFE shown in Equations 26 and 27, an HDV calibration curve can be constructed as described in the theory section. Then secondary molecular weight curves can be constructed for other polymers of interest by the methods discussed in the theory section as was done in Ref. 1, using the indirect PMMA molecular weight calibration curve. 

In SEC, universal calibration is often utilized to characterize a molecular weight distribution. For a universal calibration curve, one must determine the product of log(intrinsic viscosity molecular weight), or log([7j] M). The universal calibration method originally described by Benoit et al. (9) employs the hydro-dynamic radius or volume, the product of [tj] M as the separation parameter. The calibration curves for a variety of polymers will converge toward a single curve when plotted as log([7j] M) versus elution volume (VJ, rather than plotted the conventional way as log(M) versus V, (5). Universal calibration behavior is highly dependent on the absence of any secondary separation effects. Most failures of universal calibration are normally due to the absence of a pure size exclusion mechanism. 

High-molecular-weight aliphatic amines are used extensively in many industries. The total primary- and secondary-amine content of aliphatic amines can be determined easily and rapidly by functional-group analysis in the near infrared [9], using chloroform solvent and 5-cm fused-silica cells. Primary amines have characteristic absorption maxima at 2.02 /um and 1.55 m, whereas secondary amines absorb only at 1.55 fim. Quantitation is achieved by the calibration-curve method using a series of standard solutions of primary and of secondary amines. Most other methods for the determination of total primary, secondary, or tertiary amine in a mixture are lengthy or inaccurate, or are unsuitable for small samples. 

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