Field‐Flow Fractionation in Analysis of Polymers and Rubbers

Abstract

Field‐flow fractionation (FFF) was conceived by J. Calvin Giddings in 1966 as a separation and characterization method for macromolecules, colloids, and particulates. Similar to chromatography, sample migration is caused by differential interaction with a field acting along an axis orthogonal to that of the transport liquid. Unlike chromatography, where separation is achieved by solutes partitioning between mobile and stationary phases, separation in FFF arises from the distribution of sample components in fluid laminae flowing at different velocities in a single phase. The different flow velocities, described by a parabolic profile, arise from the high aspect ratio of the FFF channel. Different types of fields can be used in FFF as long as they interact with some physicochemical property of the sample. The FFF channel design makes it highly suited for analyses of fragile aggregates, high‐molecular‐weight polymers, and gels. In comparison with packed columns, shear rates in the channel and the probability of plugging the channel are low. The ability of thermal FFF to differentiate polymers and latexes of different bulk and surface composition is unique among currently used separation techniques. The FFF family of techniques can provide a great deal of information about the sample but an initial time investment is often required for method development.In this article, the fundamental mechanism of FFF is shown at play in the separation and characterization of polymers and rubbers by the two techniques par excellence in this field: flow FFF and thermal FFF.

Polyion Complex-Templated Synthesis of Cross-Linked Single-Enzyme Nanoparticles

“…AF4 is an open-channel separator, which does not contain a stationary phase. It could avoid the undesired shear degradation of unstable and fragile PIC particles caused by stationary phase and achieve high accuracy of fractionation. , Because of this, the PIC particles could be separated from the other components in the mixture (such as free polymer) without breaking them apart through excessive shear. The separated components can then be characterized independently by on-line UV–vis/RI/MALS.…”

The Core–Shell Structure, Not Sugar, Drives the Thermal Stabilization of Single-Enzyme Nanoparticles

“…AF4 is an open-channel separator, which can achieve high accuracy of fractionation while avoiding the undesired shear deduction of the fragile structure of PIC micelles caused by the stationary phase of the normal separator like GPC. 67,68 By using this separator, the structural integrity of SENs remains intact when separated from the other potential components in the solution (such as free polymer and nonencapsulated GOx). The separated components can then be characterized independently by online UV−Vis/RI/MALS.…”

“…To confirm the presence of SENs, as opposed to higher-order aggregates, we proceeded to analyze the size change in the mixtures by asymmetric flow field-flow fractionation (AF4) in combination with MALS as a function of polymer concentration. AF4 is an open-channel separator, which can achieve high accuracy of fractionation while avoiding the undesired shear deduction of the fragile structure of PIC micelles caused by the stationary phase of the normal separator like GPC. , By using this separator, the structural integrity of SENs remains intact when separated from the other potential components in the solution (such as free polymer and non-encapsulated GOx). The separated components can then be characterized independently by online UV–Vis/RI/MALS.…”