Abstract
This research work is focused on the development of
instrumentation, operation, and approximate theory of a
new continuous twodimensional thermal fieldflow
fractionation (2DThFFF) technique for separation and
collection of macromolecules and particles. The
separation occurs in a thin diskshaped channel, where a
carrier liquid flows radially from the center towards the
perimeter of the channel and a steady stream of the
sample solution is introduced continuously at a second
inlet close to the centre of the channel. Under influence
of the thermal field, the sample components are separated
in radial direction according to the analytical ThFFF
principle. Simultaneously, the lower channel wall is
rotating with respect to the stationary upper wall, when
a sheardriven flow profile deflects the separated sample
components into continuous trajectories that strike off
at different angles over the 2D surface. Finally, the
sample components are collected at the outer rim of the
channel, and the sample concentrations in each fraction
are determined using the analytical ThFFF. The samples
were polystyrene polymer standards and the carrier
solvents cyclohexane and cyclohexaneethylbenzene mixture
in continuous 2DThFFF and tetrahydrofuran in analytical
ThFFF.
Positive effect of the thermal field on the sample
deflection was observed, although broadening of the
sample zone was observed. By decreasing the channel
thickness and the radial and angular flow rate of the
carrier, the zone broadening was significantly narrowed.
The systematic variation of the experimental parameters
allowed to determine the conditions required for the
continuous fractionation of polystyrene polymers
according to their molar masses. As an example, almost
baseline separation was achieved with two polystyrene
samples of different molar masses.
Meanwhile, an approximate theoretical model was developed
for prediction the trajectory of the sample component
zone and its angular displacement under various operating
conditions. The trends in the deflection angles without
and with a thermal gradient were qualitatively in
agreement with predictions of the model, but significant
quantitative differences between the experimental results
and theoretical predictions were also found. The reasons
for discrepancies between the theory and the experiment
could be the following: the sample is already relaxed at
the sample inlet, effect of solvent partition using
binary solvent as the carrier, dispersion of the sample,
the instrumental limitations, and/or geometrical
imperfections. However, the theoretical model will
provide quidelines for future interpretation and
optimization of separations in continuous 2DThFFF method
Original language  English 

Qualification  Doctor Degree 
Awarding Institution 

Supervisors/Advisors 

Award date  9 May 2014 
Place of Publication  Helsinki 
Publisher  
Print ISBNs  9789521098925 
Electronic ISBNs  9789521098932 
Publication status  Published  2014 
MoE publication type  G5 Doctoral dissertation (article) 
Keywords
 Fieldflow fractionation
 continuous fractionation
 twodimensional separation
 thermal gradient
 polystyrene
 polymer
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Vastamäki, P. (2014). Development of continuous twodimensional thermal fieldflow fractionation for polymers: Dissertation. University of Helsinki. http://urn.fi/URN:ISBN:97895298932