Epc. Mes et al., Sub-micron particle analysis by thermal field-flow fractionation and multi-angle light scattering detection, CHROMATOGR, 53(11-12), 2001, pp. 697-703
Thermal field-flow fractionation (ThFFF) coupled to multi-angle light scatt
ering (MALS) detection has been used to analyse sub-micron particles. Polys
tyrene and styrene-butylmethacrylate latices of various composition were st
udied as well as different swellable core-shell particles. Using ThFFF-MALS
, thermal diffusion coefficients (D-T) of particles could be calculated dir
ectly without need for additional dynamic light scattering (DLS) measuremen
ts. The Soret coefficient was determined from ThFFF data while MALS provide
d the particle radius of gyration allowing calculation of the particle diff
usion coefficient. Combining both data gave the thermal diffusion coefficie
nt It was demonstrated that differences in the particle chemical compositio
n can lead to differences in thermal diffusion. However, no clear trend was
observed, and as thermal diffusion is still poorly understood, it is diffi
cult to correlate chemical composition with D-T. Apart from the influence o
f the chemical composition of the particles, it was found that the pH of th
e carrier solution also had a strong effect on thermal diffusion.
Although thermal diffusion will be mainly determined by the particle surfac
e composition, study of core-shells showed that swelling of the outer layer
of the particle does not significantly influence thermal diffusion.
To calculate diffusion coefficients for complex core shells, DLS measuremen
ts were still required. Combination of DLS and ThFFF-MALS data gave insight
into the swelling behaviour of core-shells and their internal structure.