Thermal Field-flow Fractionation Research Articles

On the Focusing Mechanism in Thermal Field-Flow Fractionation of Macromolecules

On the Focusing Mechanism in Thermal Field-Flow Fractionation of Macromolecules

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.

Study of MHD nanofluid flow with fuzzy volume fraction in thermal field-flow fractionation

This paper discusses the magnetohydrodynamic Jeffery–Hamel nanofluid flow (MHD-JHNF) between two rigid non-parallel plane walls. It enhances the study of simple Jeffery–Hamel flow problems to the MHD nanofluid flow problems with uncertain volume fractions. It examines the impact of various parameters, such as channel angles and Reynolds number with magnetic field and nanoparticles, on the fuzzy velocity profiles. The nanoparticle volume fraction is considered an uncertain parameter by using a triangular fuzzy number ranging from 0.0 to 0.2. A novel double parametric form-based homotopy analysis approach with its convergence analysis is introduced to examine the fuzzy velocity profiles at distinct convergent and divergent channel positions and fuzzy velocity boundaries at other channels and illustrates the efficiency of the process. Finally, Maple software is used to make the numerical simulations, and the results are checked with the available results for specific cases in crisp environments.

Unravelling the thermo-responsive evolution from single-chain to multiple-chain nanoparticles by thermal field-flow fractionation

ThFFF with multiple detection enables monitoring the transformation of block copolymers into single chain nanoparticles stabilized by a shell (SCNP-shell). The SCNP-shell are in dynamic equilibrium with multiple chain nanoparticles.

Correction to: Thermal Field-Flow Fractionation as a Powerful Tool for the Fractionation of Complex Synthetic Polymers: A Perspective

Correction to: Thermal Field-Flow Fractionation as a Powerful Tool for the Fractionation of Complex Synthetic Polymers: A Perspective

Thermal Field-Flow Fractionation as a Powerful Tool for the Fractionation of Complex Synthetic Polymers: A Perspective

Synthetic polymers have complex molecular structures with distributions in molar mass, chemical composition, functionality and molecular topology. For the comprehensive analysis of polymer structures, a number of advanced spectroscopic and fractionation techniques are used. For the fractionation of polymers, most frequently column-based methods are applied. These are of limited value for the separation of very high molar mass and fragile analytes. Thermal field-flow fractionation (ThFFF) as a channel-based method has developed into a powerful alternative and complementary technique to column-based fractionations. This perspective discusses novel applications of ThFFF and highlights its potential for the fractionation of polymer assemblies such as micelles, vesicles and nanogels.

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

The impact of electron beam irradiation on thermoplastic polyurethane material was studied for both an aliphatic and an aromatic polyurethane with approximately equal molar amount of hard and soft segments. Irradiation doses up to 300 kGy (kilogray) at room temperature and at 100 °C were applied. Changes in chemical structure, molar mass and size were assessed using infrared spectroscopy, differential scanning calorimetry, size-exclusion chromatography and thermal field-flow fractionation. Material alterations were correlated with trends regarding to degradation, crosslinking or branching changes. Thereby, limits of characterization by size exclusion chromatography are addressed and amended by thermal field-flow fractionation studies. In addition, a thermophoretic analysis has been carried out complementary to the portfolio of analytical methods applied in this work.

The Role of Solubility in Thermal Field-Flow Fractionation: A Revisited Theoretical Approach for Tuning the Separation of Chain Walking Polymerized Polyethylene.

The influence of the polymer solubility on the separation efficiency in thermal field-flow fractionation (ThFFF) was investigated for a polymer model system of differently branched chain walking polyethylenes in five different solvents, which were selected depending on their physical parameters. The understanding of polymer thermal diffusion has been elucidated using a revisited approach based on the latest thermal diffusion prediction model by Mes, Kok, and Tijssen combined with the Hansen solubility theory. Thereby, a significant improvement in the precision of the thermal diffusion prediction and the separation efficiency has been achieved by implementation of the temperature dependency on Hansen solubility parameters. In addition, we demonstrate a method for validation of the segmental size of polymer chains with varying topology by using the revisited thermal diffusion prediction approach in inverse mode and experimental thermal diffusion data.

Non-Parabolicity correction for fifty-nine solvents and a retention study for strongly distorted flow-profiles in thermal field-flow fractionation

The non-parabolicity correction of the laminar flow profiles was numerically calculated for fifty-nine solvents. The exact flow profiles were simulated based on sophisticated experimental literature data of dynamic viscosity and thermal conductivity and their dependency on the temperature in between cold wall temperatures of –10 °C up to 120 °C and temperature gradients up to ΔT = 120 K. Based on this computation the polynomial coefficients for the calculation of the non-parabolicity parameter ν is tabulated for each solvent. For this calculation a third-degree polynomial velocity profile was applied, which approximates in a good agreement the exact profile for moderately distorted flow profiles. Instead, for strongly distorted flow profiles a more exact solution with keeping ν as only adjustable parameter is proposed. Additionally, an empirically derived solution is presented to calculate the dimensionless retention parameter λ in fair accuracy directly from retention data.

Two-dimensional fractionation of complex polymers by comprehensive online-coupled thermal field-flow fractionation and size exclusion chromatography

Thermal field-flow fractionation (ThFFF) was successfully coupled online to size exclusion chromatography (SEC) in a comprehensive two-dimensional configuration. In the first dimension, fractionation according to chemical composition based on the interplay of thermal and translational diffusion took place in the ThFFF channel. Fractions from the first dimension were comprehensively transferred to the second dimension, SEC, and separated according to hydrodynamic volume which is a function of molar mass. To illustrate the capabilities of this novel two-dimensional fractionation approach, polystyrene-poly (methyl methacrylate) block copolymers were comprehensively fractionated and characterized. Blends of homopolymers, homo- and copolymers, and copolymers with different compositions were fractionated and the effects of experimental conditions, the components’ molar masses and compositions were investigated.The results illustrated the molar mass independence of the thermal diffusion coefficient in ThFFF. Translational diffusion coefficients were quantitatively determined via dynamic light scattering. The study aimed at proving the versatility of the comprehensive online coupling of ThFFF and SEC for the analysis of complex polymers having the ability to provide detailed molecular information (chemical composition and molar mass distribution) as well thermal and translational diffusion information in a single analysis. Finally, the merits of using information-rich detectors are highlighted.

Research on method of gravity thermal coupling field-flow fractionation based on symmetric encryption algorithm

The most frequently used method includes the gravity field-flow separation and thermal field-flow separation. By analyzing the influence of velocity of carrier flow on the separation effect of gravity field flow, we can know that the movement track of particle in different carrier liquid elution speed was significantly different when the external carrier liquid was continuously injected into the gravity field-flow separation channel, so the additional lift force generated by the thermal field was used to enhance the driving lift force of particles in carrier liquid and the effect of field-flow separation, and thus to achieve the gravity thermal coupling field-flow separation. In order to ensure the accuracy of field-flow separation, the computer vision detection system was used to detect the separation effect of gravity thermal coupling field flow. In this process, the symmetrical encryption optimization algorithm based on 3D cat mapping was used to realize image encryption through image scrambling and image mixing, so as to ensure the integrity of image. Experimental results show that the gravity thermal-coupled field-flow separation method based on symmetric encryption algorithm can separate the starch particles with different sizes effectively, which is suitable for the purification of powdery particles.

Characterization of Complex Branched Polymers by Multidetector Thermal Field-Flow Fractionation.

Size exclusion chromatography (SEC) for the molar mass analysis of polymers is of limited use for the analysis of branched polymers due to the co-elution of linear and branched molecules with similar hydrodynamic sizes but different molar masses. Thermal field-flow fractionation (ThFFF) in combination with multiple detection methods is a versatile alternative to SEC due to the fact that fractionation is not based entirely on molecular size but the interplay of thermal and translational diffusion that depend on molecular topology and molecular size. Multidetector ThFFF is used to investigate the correlation of branching and molar mass by determining polymer conformations from Mark-Houwink plots and the degrees of branching using functionality plots. The suitability of this approach is demonstrated for a set of 3-, 4-, and 6-arm star polystyrenes as well as a more complex hyperbranched polybutadiene-polystyrene copolymer. It is shown that ThFFF is a powerful tool for the analysis of the radius of gyration and the hydrodynamic radius when coupled online to static light scattering, viscometry, and dynamic light scattering. Shape factors are evaluated as influenced by branching where narrow dispersed star polystyrenes are used as model systems for the analysis of the more complex hyperbranched polybutadiene-polystyrene copolymer.

Topology Analysis of Chain Walking Polymerized Polyethylene: An Alternative Approach for the Branching Characterization by Thermal FFF

Thermal field-flow fractionation (ThFFF) was designed to investigate the retention behavior of a series of dendritic polyethylenes synthesized using a chain walking catalyst (cwPE) with variations ...

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

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 (DT and ST, 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 ST of a branched polymer to the ST 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.

Application of microstructured membranes for increasing retention, selectivity and resolution in asymmetrical flow field-flow fractionation

In the present proof-of-concept study, we demonstrate that retention time, selectivity and resolution can be increased in asymmetrical flow field-flow fractionation (AF4) by introducing microstructured ultrafiltration membranes. Evenly spaced micron-sized grooves, that are placed perpendicular to the channel flow on the accumulation wall of a field-flow fractionation system, cause a decrease in the zone velocity which is stronger for larger solutes. This has been demonstrated in thermal field-flow fractionation, and we prove that this is also the case in AF4. We examine the hypothesis theoretically and experimentally, by both computational and physical experiments. By means of moment analysis, we derive theoretically a set of equations which, under certain conditions, describe the mass transport and relate retention time, selectivity and plate height to the dimensions of the grooves. Physical experiments are carried out using microstructured polyethersulfone membranes fabricated by hot embossing, and the experimental results are compared with computational fluid dynamics experiments.

Thermal Field-Flow Fractionation with Quintuple Detection for the Comprehensive Analysis of Complex Polymers.

With a constantly increasing complexity of macromolecular structures, advanced polymer analysis faces new challenges with regard to the comprehensive analysis of these structures. Today it goes without saying that comprehensive polymer analysis requires selective and robust fractionation methods in combination with a set of information-rich detectors. Thermal field-flow fractionation (ThFFF) has proven to be a powerful technique for the fractionation of complex polymers as well as polymer assemblies. In the present study, ThFFF is coupled to a set of five detectors to simultaneously provide quantitative information on a number of important molecular parameters, including molar mass, molecular size, chemical composition, molecular topology, intrinsic viscosity, and normal and thermal diffusion coefficients. The five-detector setup includes a triple detector device (multiangle light scattering (MALS), differential refractive index (dRI), and differential viscometer (dVis)) that is coupled to an ultraviolet (UV) detector for dual concentration detection and an online dynamic light scattering (DLS) detector. Triple detection consisting of MALS, dRI, and dVis provides information on molar mass, molecular size, and molecular topology. Dual concentration detection offers compositional analysis from a combination of UV and dRI detectors, whereas DLS provides information on diffusion coefficients and hydrodynamic radii. The power of this novel quintuple detector ThFFF (ThFFF-QD) is documented for three important fields of application, namely, the comprehensive analysis of (1) linear and star-shaped polymers, (2) hydrogenated and deuterated polymers, and (3) block copolymer self-assemblies. These applications highlight the novel approach of determining the most relevant molecular parameters, including Mark-Houwink and conformation plots, simultaneously in a single experiment.

Application of Multidimensional Analysis Methods to Dead Oil Characterization on the Basis of Data on Thermal Field-Flow Fractionation of Native Asphaltene Nanoparticles

Molecular-mass distribution curves of native nanoasphaltenes in the form of fractograms for a significant sample of crude oils have been obtained using the thermal field-flow fractionation of asphaltenes, and a multidimensional analysis of the fractionation data has been carried out in order to construct calibration models for predicting the physicochemical properties of the studied oils.

Online coupling of thermal field-flow fractionation and Fourier transform infrared spectroscopy as a powerful tool for polymer characterization

The rapid growth and increasing importance of complex polymers has accelerated the need for advancement in characterization techniques. The analysis of such materials is challenging and the determination of different molecular parameters requires the combination of different advanced analytical techniques. Preferably, coupled and hyphenated techniques are used that provide different molecular parameters simultaneously in one experiment.Complementary to column-based fractionation techniques, channel-based methods such as thermal field-flow fractionation (ThFFF) are attractive as they can address different molecular parameters for a variety of analytes ranging from single macromolecules to macromolecular assemblies and nanoparticles. In the past, ThFFF has been coupled to a variety of size (molar mass) sensitive detectors such as multiangle laser light scattering and dynamic light scattering. Now, for the first time, the online coupling of ThFFF to Fourier transform infrared (FTIR) spectroscopy is presented. Different from standard single- or dual-wavelength IR detectors, this detector provides full spectra over the complete mid infrared range that can be used for concentration detection as well as chemical composition information. The applicability of online multidetector ThFFF-FTIR is demonstrated for selected polymer blends and copolymers comprising styrene and methyl methacrylate.

Stereocomplexation of Polymers in Micelle Nanoreactors As Studied by Multiple Detection Thermal Field-Flow Fractionation.

In this study the thermally induced in situ stereocomplexation (SC) of binary blends of symmetrical isotactic and syndiotactic polymethymethacrylates (i- and s-PMMAs) inside micellar nanoreactors (MNR) with polystyrene (PS) shells is investigated using thermal field-flow fractionation (ThFFF) as a separation technique. The MNRs are prepared from three systematic binary blending ratios of pure micelles of i-PMMA-PS and s-PMMA-PS in a nonsolvent for PMMAs in order to produce mixed micelles with a binary microstructural composition of the interior PMMA cores. The SC of these stereoregular PMMA cores inside the MNRs is shown to be thermally induced as a function of annealing temperatures from room temperature up to 150 °C. This SC is initially confirmed by Fourier transform infrared spectroscopy (FTIR), whereby signal shifts are observed in the carbonyl absorption regions. These signal shifts are as a result of SC interactions between adjacent ester and alpha-methyl groups. Furthermore, temperature-dependent dynamic light scattering (DLS) results show that MNRs with more SC domains have a much more drastic reduction in size. Additional corroboration is provided by multiple detection ThFFF results which show significant differences in retentions and sizes between MNRs with stereocomplexed cores and those without. Ratios of i-PMMA:s-PMMA in the order of 1:1, 1:2, and 2:1 were investigated with all ratios exhibiting thermal annealing induced SC, of which the 1:2 ratio is shown to have the highest predisposition to SC.

Composition-Based Separation of Pt–Fe3O4 Hybrid Nanoparticles by Thermal Field-Flow Fractionation

Colloidal hybrid nanoparticles integrate two or more material domains into a single construct to achieve multifunctionality and synergistic properties. The synthesis of these complex multicomponent hybrid nanoparticles often yields size and composition distributions that subsequently impact observed properties and complicate structure–function studies. Analyses of nanoparticle systems such as these that contain multiple simultaneously occurring distributions are highly challenging. In this work, we introduce thermal field-flow fractionation (ThFFF) as an analytical method to separate and characterize iron oxide (Fe3O4), platinum (Pt), and multicomponent platinum–iron oxide (Pt–Fe3O4) hybrid nanoparticles by composition. The transport of matter by a temperature gradient or thermal diffusion is exploited in the ThFFF separation and characterization of inorganic nanoparticles. Thermal diffusion coefficient (DT) values are determined from measured ThFFF retention times and translational diffusion coefficients...