Fractionation of Poly(butyl methacrylate) by Molecular Topology Using Multidetector Thermal Field‐Flow Fractionation

Abstract

Thermal field-flow fractionation (ThFFF) is an interesting alternative to column-based fractionation being able to address different molecular parameters including size and composition. Until today it has not been shown to be able to fractionate polymers of similar molar masses and chemical compositions by molecular topology. The present study demonstrates that poly(butyl methacrylates) with identical molar masses can be fractionated by ThFFF according to the topology of the butyl group. The influence of the solvent polarity on the thermal diffusion behavior of these polymers is presented and it is shown to have a significant influence on the fractionation of poly(n-butyl methacrylate) and poly(t-butyl methacrylate). Fractionation improves with increasing solvent polarity and solvent polarity may have a greater influence on fractionation than solvent viscosity. It is found that the thermal diffusion coefficient, D(T), as well as the hydrodynamic diameter, D(h), exhibit increasing trends with increasing solvent polarity. The solvent quality has a significant influence on the fractionation. It is found that cyclohexane, being a theta solvent for poly(t-butyl methacrylate) but not for poly(n-butyl methacrylate), significantly improves the fractionation of the samples by decreasing the diffusion rate of the former but not the latter.

Multidetector Thermal Field-Flow Fractionation for the Characterization of Vinyl Polymers in Binary Solvent Systems

“…Previous studies on microstructure-based separations by ThFFF showed that a theta solvent can be a promising solvent to significantly influence retention behavior because polymer–solvent interactions are significantly different for a theta solvent at various temperatures (especially at the theta temperature) than for a thermodynamically good solvent. − ,, Thus, CH was selected for this study as it is a theta solvent for PS.…”

“…Thermal field-flow fractionation (ThFFF) is a subtechnique of the field-flow fractionation family that employs a temperature gradient perpendicular to a carrier liquid flowing through an open, ribbon-like channel in order to fractionate analytes according to size, chemical composition and microstructure. − The applied temperature gradient drives analytes from the hot wall toward the cold wall (accumulation wall) of the channel. This temperature-induced migration is termed thermal diffusion and is described by the thermal diffusion coefficient, D T, which (among other factors) is dependent on the chemical nature of the analytes and the solvent. ,,, Thermal diffusion is balanced by normal diffusion which is the migration of analytes away from the accumulation wall toward the center of the channel due to increasing analyte concentration. , Normal diffusion is described by the normal diffusion coefficient, D , and is dependent on the size of the analytes in solution. ,, …”

Characterisation of block copolymer self‐assemblies by thermal field‐flow fractionation

“…ThFFF is a sub‐technique of FFF that applies a temperature drop across an open, ribbon‐like channel in order to fractionate analytes according to size, chemical composition and microstructure . The first reported attempts to fully utilise the advantages and unique separation capabilities of ThFFF to separate micelles according to corona composition were performed on poly(methyl methacrylate)–polystyrene micelles in acetonitrile using a multidetector ThFFF setup as illustrated in Scheme .…”