for HT-GPC is specially made to stand high temperatures. HT-GPC allows the measurement of average MWs and MWDs of polymers that will not dissolve in GPC solvents at conventional GPC temperatures. For analysis at high temperature, it is necessary to prepare standards at the same experimental conditions as used to prepare the normal samples; the standards commonly used for high temperatures are polystyrene and polybutadiene, among others. The effect of the temperature on the elution peak position is presented in Figure 17.5 for eight PS standards at three different temperatures [27]. When the samples are analyzed above room temperature, the elution peak presents a shift to lower values, which is indicative of the fact that the volume of the pore is also reduced as a result of the thermal expansion of the eluent and the packing materials. As can be seen, the elution time diminishes as the temperature increases in the column, an effect which is larger for a lower MW. The magnitude of the peak gets relatively small for the higher MW samples. It is usually reported that the width of the elution peak decreases significantly as the column temperature increases, which is attributed to the facilitated mass transfer of the polymer chains. As a result of the reduced width, a better resolution is obtained in the chromatograms when high temperature SEC is used.
for HT-GPC is specially made to stand high temperatures. HT-GPC allows the measurement of average MWs and MWDs of polymers that will not dissolve in GPC solvents at conventional GPC temperatures. For analysis at high temperature, it is necessary to prepare standards at the same experimental conditions as used to prepare the normal samples; the standards commonly used for high temperatures are polystyrene and polybutadiene, among others. The effect of the temperature on the elution peak position is presented in Figure 17.5 for eight PS standards at three different temperatures [27]. When the samples are analyzed above room temperature, the elution peak presents a shift to lower values, which is indicative of the fact that the volume of the pore is also reduced as a result of the thermal expansion of the eluent and the packing materials. As can be seen, the elution time diminishes as the temperature increases in the column, an effect which is larger for a lower MW. The magnitude of the peak gets relatively small for the higher MW samples. It is usually reported that the width of the elution peak decreases significantly as the column temperature increases, which is attributed to the facilitated mass transfer of the polymer chains. As a result of the reduced width, a better resolution is obtained in the chromatograms when high temperature SEC is used.
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