Chemistry Reference
In-Depth Information
Figure 1.
Schematic diagram of the new automated crossfractionation instrument. Injection valve shown in ''load''
position A; ''inject'' position marked as B.
each temperature, and after a given dis-
solution time, the injection valve is
switched to the ''inject'' position in order
to allow the solvent to elute the dissolved
polymer from the TREF column. Once that
fraction is eluted, the injection valve is
closed again to ''load'' position so that the
flow through the TREF column is stopped.
Then, the oven temperature is increased to
start dissolving the fraction that will be
eluted in the next step.
Following that process, different TREF
fractions with increasing crystallinity are
injected into the GPC columns, where they
are fractionated this time according to
molar mass. An IR4 infrared detector is
used to record the final chromatograms
continuously, as depicted in Figure 3, where
the raw IR detector and oven temperature
signals from a real experiment are plotted.
It must be noted that each of the peaks in
the IR detector signal is in fact a full GPC
Figure 2.
Temperature profile followed by the TREF oven in a typical cross-fractionation experiment with indication of the
different processes.
