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

High-Resolution Tracking of Multiple Distributions in Metallic Nanostructures: Advanced Analysis Was Carried Out with Novel 3D Correlation Thermal Field-Flow Fractionation

Multifunctional metallic nanostructures are essential in the architecture of modern technology. However, their characterization remains challenging due to their hybrid nature. In this study, we present a novel photoreduction-based protocol for augmenting the inherent properties of imidazolium-containing ionic polymers (IIP)s through orthogonal functionalization with gold nanoparticles (Au NPs) to produce IIP_Au NPs, as well as novel and advanced characterization via three-dimensional correlation thermal field-flow fractionation (3DCoThFFF). Coordination chemistry is applied to anchor Au³⁺ onto the nitrogen atom of the imidazolium rings, for subsequent photoreduction to Au NPs using UV irradiation. Thermal field-flow fractionation (ThFFF) and the localized surface plasmon resonance (LSPR) of Au NPs are both dependent on size, shape, and composition, thus synergistically co-opted herein to develop mutual correlation for the advanced analysis of 3D spectral data. With 3DCoThFFF, multiple sizes, shapes, compositions, and their respective distributions are synchronously correlated using time-resolved LSPR, as derived from multiple two-dimensional UV-vis spectra per unit ThFFF retention time. As such, higher resolutions and sensitivities are observed relative to those of regular ThFFF and batch UV-vis. In addition, 3DCoThFFF is shown to be highly suitable for monitoring and evaluating the thermostability and dynamics of the metallic nanostructures through the sequential correlation of UV-vis spectra measured under incremental ThFFF temperature gradients. Comparable sizes are measured for IIP and IIP_Au NPs. However, distinct elution profiles and UV-vis absorbances are recorded, thereby reaffirming the versatility of ThFFF as a robust tool for validating the successful functionalization of IIP with Au to produce IIP_Au NPs.

Field-Flow Fractionation: Extended Frontiers to Supramolecular and Complex Polymer Materials

In this extended special feature to celebrate the 35th anniversary edition of LCGC Europe, leading figures from the separation science community explore contemporary trends in separation science and identify possible future developments.

New Advances and Applications in Field-Flow Fractionation

Field-flow fractionation (FFF) is a family of techniques that was created especially for separating and characterizing macromolecules, nanoparticles, and micrometer-sized analytes. It is coming of age as new nanomaterials, polymers, composites, and biohybrids with remarkable properties are introduced and new analytical challenges arise due to synthesis heterogeneities and the motivation to correlate analyte properties with observed performance. Appreciation of the complexity of biological, pharmaceutical, and food systems and the need to monitor multiple components across many size scales have also contributed to FFF's growth. This review highlights recent advances in FFF capabilities, instrumentation, and applications that feature the unique characteristics of different FFF techniques in determining a variety of information, such as averages and distributions in size, composition, shape, architecture, and microstructure and in investigating transformations and function.

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

New branched polymerisations offer previously inaccessible macromolecules and architectural understanding is important as it provides insight into the branching mechanism and enables the determination of structure-property relationships. Here we present a detailed inverse gated 13C NMR characterisation of materials derived from the very recently reported Transfer-dominated Branching Radical Telomerisation (TBRT) approach to quantify branching and provide an insight into cyclisation.

Semiquantitative Approach for Polyester Characterization Using Matrix-Assisted Laser Desorption Ionization/Time-of-Flight Mass Spectrometry Approved by 1H NMR

Matrix-assisted laser desorption ionization/time-of-flight (MALDI/ToF) mass spectrometry and ¹H NMR were used for the structural investigation of isophthalic and maleic acid copolyesters with neopentyl glycol. Since both methods provided information on the ratio of incorporated acid components and terminating groups, results were compared and linear correlations (R² = 0.96-0.98) could be found. This suggests that MALDI/ToF MS is a suitable tool for the semiquantitative characterization of polyester systems. For the isophthalic/maleic acid ratio, MALDI results yielded constantly lower values than ¹H NMR, which was attributed to varying ionization efficiencies of homo- and copolyesters. Ratios of carboxylic and hydroxylic terminating groups, which are conventionally still measured by time consuming complex titrations, were measured with MALDI and ¹H NMR and were in good agreement. Both methods either excluded or distinguished unreacted monomers in the polyester bulk in contrast to acid-base titrations where those monomers severely distort the results. Additional structural information could be gained including the observation of cyclic structures (MALDI), E/Z isomerism from maleic to fumaric acid, and the statistical distribution of the acid components within the polyester chain (¹H NMR). While ¹H NMR peak assignments have to be verified by ¹³C NMR and multidimensional techniques, MALDI/ToF MS provides a straightforward technique that can be applied to other polyester systems without major alterations.