Thermal Field-Flow Fractionation for Characterization of Architecture in Hyperbranched Aromatic-Aliphatic Polyesters with Controlled Branching

Abstract

Thermal field-flow fractionation (ThFFF) was used to characterize the architecture of aromatic–aliphatic polyesters with varying degrees of branching. Thermal diffusion and Soret coefficients (D T and S T, respectively) provide a novel route to polymer architecture analysis. This paper demonstrates an innovative strategy to extract architecture information from the physicochemical separation parameters embedded in ThFFF retention times without explicit separation of linear and branched samples. A Soret contraction factor (g″), defined as the ratio of the S T of a branched polymer to the S T of a molecular weight equivalent linear analogue, is introduced as a metric to indicate degree of branching (DB). This approach circumvents several challenges associated with the analysis of high molar mass polymers with a high degree of branching. The g″ value is shown to be proportional to the degree of branching for linear (DB, 0%), gradually branched (DB, <50%), hyperbranched (DB, 50%), and pseudodendritic (DB, 100%) polyesters allowing the establishment of architecture calibration curves. Furthermore, positive log­(g″) values (∼0.2) at low molar mass are attributed to cyclic subpopulations. This work demonstrates the usefulness of the Soret contraction factor for statistically and hyperbranched polymer systems and its sensitivity to cyclic polymers.

Impact of Electron Beam Irradiation on Thermoplastic Polyurethanes Unraveled by Thermal Field-Flow Fractionation

“…Another indication for changes in topology, branching or changes in chemical composition is provided by the Soret coefficient ST. [22][23][24] In this study changes in ST are mainly ascribed to changes in the polymer topology, because in ATR-FTIR no significant changes accounting for transformations in chemical composition were found, even though they are supposed to be more likely seen by ATR as stated in sect. 3.1.…”

“…To overcome the challenges in SEC a change of the separation mechanism to FFF with a much broader separation range may be a helpful alternative as it has been reported previously. 19,79 Among the various FFF sub techniques, ThFFF may provide further information about intrinsic material properties such as differences in chemical composition 19,25,29 (with changed solvent interaction) or differences in topology [22][23][24]29 by the means of thermophoresis. ThFFF is a valuable complementary technique despite its separation range does not completely cover the range of SEC for low molar masses (see, Fig S19 , SI).…”

“…Depending on the nature of the force field, a separation e. g. according to hydrodynamic size (AF4), effective mass (SdFFF), electrophoretic mobility (ElFFF) or thermal diffusion (ThFFF) can be realized. 21 For this study we have chosen ThFFF since this separation technique can be highly selective for changes in the polymer's topology [22][23][24] and/or chemical composition. [25][26][27][28][29] Details on the basic separation principle are given elsewhere 21,30 and in the supporting information (SI, section 1).…”

Quantification of branching within high molecular weight polymers with polyester backbones formed by transfer-dominated branching radical telomerisation (TBRT)

“…This includes studying the development of branched structures, 51 branching density 52 or calculating degree of branching 53,54 or average number of branches. 55 Techniques such as size exclusion chromatography, [56][57][58][59] light scattering 60 techniques, thermal eld-ow fractionation, 61,62 hydrolysis/ analysis 63 of branched structures and measurement using advanced nuclear magnetic resonance spectroscopy (NMR) techniques 64,65 of either the direct polymerisation product or aer post-polymerisation reaction of unreacted functional groups 66,67 have been reported for a wide range of material chemistries. The factors that confound accurate branching evaluation distribution include the overlap of critical NMR resonances and the presence of a distribution of architectures within the polymer molecular weight distribution.…”

Characterization of Complex Branched Polymers by Multidetector Thermal Field‐Flow Fractionation

“…The retention factor in this case is the Soret coefficient ( S T = D T / D ) . Recently, branching analysis has been addressed using asymmetric flow and thermal field‐flow fractionations …”