Sample overloading effects in polymer characterization by field‐flow fractionation

Abstract

SynopsisThere are two subtechniques of field-flow fractionation (FFF), thermal FFF and flow FFF, that have been successfully employed for polymer fractionation and characterization. These techniques are primarily analytical in nature, yielding accurate polymer characteristics from small sample loads ( -10 pg or less, depending on detection sensitivity). In this study the effects of increasing sample size are examined. Modest increases in load are found to result in shifts toward higher retention volumes. These modest loads also result in some broadening of the sample peaks without a major loss of peak symmetry. Excessive loading, by contrast, appears to give rise both to skewed peaks and to new artifact peaks at higher levels of retention. These observations are discussed in terms of the concentration dependence of various properties (viscosity, diffusivity, thermal diffusivity) which influence polymer transport through the FFF channel. The results are used to indicate upper limits to suitable sample concentrations.

Onset of sample concentration effects on retention in field‐flow fractionation

“…This is the case for polystyrenes in ethylbenzene [5,27], in THF [10,17,29], or in decalin [35], as well as for polytetrahydrofurans in toluene [21] and polyisoprenes and polymethylmethacrylates in THF [29]. A similar behavior was observed for polystyrenes in ethylbenzene analyzed by flow FFF [10].…”

Conformational change and aggregation of κ-carrageenan studied by flow field-flow fractionation and multiangle light scattering

“…This is very close to the theoretical ratio FFF. 33 The r H decreased from a constant level of approximately 26 nm for the 20-100 mg loads as of 0.775 (Table I). Reasonable data for r G are thus obtained, although 8 nm can be considered to be compared with only 11 nm for the 160 mg load.…”

Study of thermal diffusion of polybutadiene and polytetrahydrofuran in various organic solvents

“…Because the polymer concentration varies strongly within the sample zone, the development of an accurate theoretical model that considers the effects of polymer concentration in ThFFF experiments is extremely complicated. 26 In this work, the concentration of the injected polymer solutions was kept low (0.2-0.25 mg/mL) to minimize systematic errors in the determination of the a/T values.26…”