Thermal field-flow fractionation (ThFFF)

Size: px

Start display at page:

Download "Thermal field-flow fractionation (ThFFF)"

Marianna Chambers
5 years ago
Views:

$92617 Thermal field-flow fractionation (ThFFF) KIM R.$

1 NAS Study: A Research Agenda for a New Era in SEPARATIONS SCIENCE May 7-8, 2018 The Beckman Center 100 Academy Way, Irvine, CA Thermal field-flow fractionation (ThFFF) KIM R. WILLIAMS DEPARTMENT OF CHEMISTRY COLORADO SCHOOL OF MINES GOLDEN, CO 80401

Field-Flow Fractionation Retention parameter λ l λ = l = w D Uw = kt F w Retention time t r 0 t Fwt t r = = 6 λ 6kT 0 1966 FIELD

2 Field-Flow Fractionation Retention parameter λ l λ = l = w D Uw = kt F w Retention time t r 0 t Fwt t r = = 6 λ 6kT FIELD for λ << 1 Electric Crossflow Dielectric Light Thermal Sedimentation Magnetic Acoustic (1984)

3 Thermal FFF separation mechanism x = w Hot wall D T ΔT x = 0 D Cold wall D T thermal diffusion coefficient D diffusion coefficient T temperature difference between hot and cold wall 3

4 ThFFF channel Hot wall Cold wall ThFFF channel: 45.6 cm x 2 cm x cm. T max ~120 DETECTORS: Light scattering (multiangle light scattering, dynamic light scattering) Concentration (UV-Vis, differential refractive index) 4

5 Thermal FFF theory Force exerted by temperature gradient F = kt D T D dt dx D T thermal diffusion coefficient D translational diffusion coefficient dt/dx temperature gradient (= T/w) Substitute F expression into t r equation (assuming well retained species) 0 D T temperature difference between T Tt tr D 6 hot and cold walls t 0 channel void time t r S T Tt 6 0 S T Soret coefficient (= D T /D) Stokes-Einstein eqn D = kt 3πηd h d h hydrodynamic diameter η liquid viscosity D measured by dynamic light Scattering (on-line) 5

6 Diffusion (size)-based ThFFF separation of polystyrene (PS) 200kDa 465kDa 1290kDa 3150kDa THF, 0.1 ml/min ΔT initial = 80C t 1 =10 min ΔT final = 5C 90kDa 28.5kDa V o Runyon, Williams, Colorado School of Mines, unpublished results 6

7 ThFFF composition separation and universal calibration via D T HOMOPOLYMERS COPOLYMERS (RANDOM, BLOCK, MIKTOARM) D ~4.0 x 10-7 cm 2 s -1 PS-PBA S.K.R. Williams, J.R. Runyon, A.A.Ashames, Anal. Chem., 83, (2011). J.R. Runyon, S.K.R. Williams, J. Chromatogr. A 1218, (2011). Copolymer D T varies proportionally with the mole fraction of monomers present. Nonselective solvent for both PS and PBA. 7

8 Thermodiffusion behavior in liquids Early works 1856 Ludwig observed decrease of salt concentration on warm side of U-shaped tube 1879 Soret did more extensive systematic studies with salt solutions 1938 Clusius-Dickel showed gas concentration differs at top and bottom of column with heated interior cylinder and cooled exterior cylinder (thermogravitational column) 1948 Debye & Bueche expts with polymers W. Kohler, K. I.Morozov, J. Non-Equilib. Thermodyn. 41, 151 (2016). 8

9 What is known about D T for (co)polymers in organic solvents? D T is independent of molecular weight (>~10 kda) Strongly affected by polymer-solvent interactions Homopolymers: Different polymer chemistries have different D T (in same solvent) Different solvents yield different D T for the same polymer chemistry Copolymers: If solvent is nonselective for both components of the diblock, copolymer, D T behavior same as random copolymer. If solvent is selective for one component, the copolymer D T is dominated by D T of the homopolymer located at the solvent interface. Schimpf, Giddings, J. Polym. Sci.: Part B Polym. Phys., 27, 1317 (1989). S-B-S-B-B-S-B-S (S-S-S-S-B-B-B-B) n Not fully understood, many theories proposed 9

10 Identifying theories for estimating polymer D T Schimpf and Semenov J. Phys. Chem. B, 104, 2000, Based on temperature-dependent pressure gradient due to small changes in solvent density around the mer Mes, Kok, Tijssen Int. J. Poly. Anal. Charact. 8, 2003, Based on temperature dependent chemical potential gradient Flory-Huggins lattice theory D T 16α T r = 27η 2 m A v o D T 2 = φ 1 D T seg T χ T T 2 α T r m A η v 0 coefficient of thermal expansion of solvent monomer radius Hamaker constant solvent viscosity mean volume of solvent occupied by one solvent molecule D seg φ 1 χ segmental diffusion coefficient (solvent viscosity) volume fraction of solvent polymer-solvent interaction parameter Runyon, Williams, J. Chromatogr. A, 1218, (2011).

11 Comparison of Measured and Theoretical S T for Linear Polymers S T,exp Linear PS, PBA, PMMA, PMA Linear PS, PBA, PMA, PMMA S T,theo NSC PBA y = 1.00x R 2 =.99 S T for linear polymers can be estimated from theory S T exp and S T theo relationship is independent of linear polymer composition PS Polystyrene PBA Polybutylacrylate PMA Polymethacrylate, PMMA Polymethylmethacrylate 11

12 Comparison of Measured and Theoretical S T for Linear Polymers S T,exp Linear PS, PBA, PMA, PMMA S T,theo PBA 2 y = 1.00x R 2 =.99 PBA 2 branching due to backbiting reactions? Intramolecular chain transfer 12

13 S T for different polymer architectures Soret contraction factor g = SS TT bbbbbbbbbbbbbbb SS TT llllllllllll Runyon, Williams, Colorado School of Mines, unpublished results 13

14 Number of Chain Ends From g g is directly correlated to the number of chain ends Linear polymer analogue is not needed! Runyon, Williams, Colorado School of Mines, unpublished results

15 MW, composition, and chain ends in a single analysis? COMPOSITION DISTRIBUTION ARCHITECTURE, MW DISTRIBUTIONS D T x 10 7 cm 2 sec -1 K Weight percent PBA Number of arms M w (kda) Retention time (min) t o t o Retention time (min) Average mole fraction Miktoarm star # arms PS/PBA Nominal 50 Nominal.44/.56 ThFFF ThFFF.43/.57 Runyon, Williams, Colorado School of Mines, unpublished results.

Separation of Hybrid Metal-Metal Oxide Nanoparticles Pt nanocubes Particle Type TEM Size (nm) D T x 10-8 (cm 2 K -1 sec -1 ) Pt-Fe3O4 nanoflowers Pt Nanocubes* 6.0 ± 0.8 0.

16 Separation of Hybrid Metal-Metal Oxide Nanoparticles Pt nanocubes Particle Type TEM Size (nm) D T x 10-8 (cm 2 K -1 sec -1 ) Pt-Fe3O4 nanoflowers Pt Nanocubes* 6.0 ± Fe3O4 nanoparticles Fe 3 O 4 Nanoparticles Pt-Fe 3 O 4 Nanoflowers 11.1 ± ± D T calculated using ThFFF theory and online DLS. * D T calculated using diffusion measured via AF4 Smith, Williams, Colorado School of Mines, unpublished results.

17 Separation of Hybrid Metal-Metal Oxide Nanoparticles Smith, Williams, Colorado School of Mines, unpublished results. 17

18 Composition Distribution for Hybrid Nanoparticles Smith, Williams, Colorado School of Mines, unpublished results. 18

19 Why Particles Move in a Thermal Field 9 Particle Parameters: Solvent Parameters: Solvent-Particle Parameters: A: Particle Surface Area Known σ 2 eff : Effective Surface Charge density Capillary Electrophoresis -Measurement β: Ionic Shielding Factor Known ε: Solvent Dielectric Constant Known λ DH : Debye-Hückel Screening Length ζ-potential or Calculation s hyd : Particle-area-specific Hydration Entropy S. Duhr, D. Braun, PNAS,. 103, (2006).

Nanoparticle composition (inorganic, metals, polymeric, core-shells) Nanoparticle shape (Pt

20 ThFFF work in progress Polymer microstructure: 1,2 versus 1,4 polybutadiene ratios and distributions Polymer architecture: differentiating linear, star, bottle brush, cyclic Nanoparticle composition (inorganic, metals, polymeric, core-shells) Nanoparticle shape (Pt cube/cuboctahedra) D T, S T measurement Thermal diffusion theory Analytes with controlled physicochemical characteristics 20

21 Challenges Whether or not polymers would show a marked thermodiffusion effect cannot be predicted, since no adequate theoretical treatment of solutions has been reported. Many attempts have been made both from the thermodynamic and kinetic points of view but they all fail to predict what a given liquid mixture will do. P. Debye and A. M. Bueche Thermal diffusion of polymer solutions in H. A. Robinson, ed., High Polymer Physics Remsen Press Div. Brooklyn, 497 (1948) Advance understanding of thermodiffusion predict S T, D T values and transport direction for different analytes, solvents, ionic strengths, T, etc. Establish benchmark S T, D T values for different categories Well characterized sample series Better detectors (low cell volumes, better sensitivity,.) W. Kohler, K. I.Morozov, J. Non-Equilib. Thermodyn. 41, 151 (2016). 21

Focusing D. Ross, L.E. Locasio, Anal. Chem.

Self propelled thermophoretic microgear M.

Ripoll, Soft Matter, 10, 1006 (2014) Use

22 Opportunities? Microfluidics Temperature Gradient Focusing D. Ross, L.E. Locasio, Anal. Chem., 74, (2002). Microscale thermophoresis S. Duhr, D. Braun, PNAS, 103, (2006). Self propelled thermophoretic microgear M.C. Yang, M. Ripoll, Soft Matter, 10, 1006 (2014) Use waste heat to effect large scale thermal diffusion-based separations? Examples of large scale processes present in nature. Untapped potential? Biological applications 1-2 K over 25 µm Controlling fluid flow by design? 22

23 23

24 Does D T Scale with Metal-Metal Oxide Surface Area Smith, Williams, Colorado School of Mines, unpublished results. 24

25 Energetic Derivations: Thermal Diffusion Theories Hydrodynamic Derivations: Theory Author Type Gradient Driver Focus Braun and Duhr Energetic Free Enthalpy ΔG (-) Electrostatics Morozov Hydrodynamic Pressure Interfacial Surface Tension Anderson Electrostatics Includes perturbations by Particle Thermal Conductivity

Dr. Christoph Johann Wyatt Technology Europe GmbH Copyright Wyatt Technology Europe GmbH All Rights reserved 1

Dr. Christoph Johann Wyatt Technology Europe GmbH 2010 Copyright Wyatt Technology Europe GmbH All Rights reserved 1 Introduction Overview The Nature of Scattered Light: Intensity of scattered light Angular