1. Comparison of the Diffusion Coefficients Obtained for Latex Film Formation Studied by FRET and Pyrene Excimer Formation Remi Casier Profs. Jean Duhamel and Mario Gauthier University of Waterloo, Waterloo, Ontario 1

2. Latex: o Stable dispersion of polymer particles in an aqueous solution Applications: o Products: gloves and tires o Additives: adhesives and paper coatings o Films: paints and coatings 2Introduction Tire tread,.http://mrg.bz/q7fSMj Painted boards,.http://mrg.bz/q7fSMj

3. Film Formation from a Latex Dispersion 3 The minimum film formation temperature (MFT) must be reached before polymer chains can interdiffuse (MFT ≈ T g ) 1 Interparticle polymer diffusion (IPD) during the coalescence of latex particles produces a homogeneous film Mechanical properties are highly dependent on the extent of IPD 2 1.Zhao, C., Wang, Y., Hruska, Z., Winnik, M. Molecular Aspects of Latex Film Formation: An Energy-Transfer Study; Macromolecules 1990, 23, 4082-4087. 2.Gauthier, C.; Guyot, A.; Perez, J.; Sindt, O. Film Formation and Mechanical Behavior of Polymer Laticies. Film Formation in Waterborne Coatings, Chapter 10, 1996, 163-178. Washington, DC: American Chemical Society. Good Mechanical Properties Poor Mechanical Properties T > MFT Stage 1: Water Evaporation Stage 2: Particle Deformation Stage 3: Coalescence

4. 4 Background Previous studies of latex film formation by the Winnik group have primarily used fluorescence resonance energy transfer (FRET) to probe IPD 1-2 Two dyes used: Phenanthrene as a donor (D) and anthracene as an acceptor (A) Time resolved fluorescence decays are obtained for various annealing times 1.Zhao, C.; Wang, Y.; Hruska, Z.; Winnik, M. A. Molecular Aspects of Latex Film Formation: An Energy-Transfer Study; Macromolecules 1990, 23, 4082-4087. 2. Wang, Y.; Winnik, M. A. Energy-Transfer Study of Polymer Diffusion in Melt-Pressed Films of Poly(methyl methacrylate); Macromolecules 1993, 26, 3147-3150. D D D D D D A A A A D A A A IPD T > MFT

5. Develop a simpler method to probe the minimum film formation temperature (MFT) and the degree of interparticle polymer diffusion (IPD) in latex films Using a fluorescently-labeled latex with an emission that changes depending on the degree of IPD A single fluorophore pyrene (Py) can be used, thus only a single fluorescently-labeled latex must be prepared 5 Objective

6. Pyrene Fluorescence IMIM IEIE Excimer Monomer I E /I M – a measure of the amount of excimer formed 6 Monomer EmissionExcimer Emission

7. 7 Interparticle Polymer Diffusion Using Pyrene t=0 t˃0 High C py Low C Py High excimer formation Low excimer formation High I E /I M ratio Low I E /I M ratio T > MFT Py

8. 8 Pyrene Labeled Latex PyEG 3 MA Hydrophobicity of the monomer was tuned by varying the length of the oligo(ethylene glycol) unit 3 x1-x 3 Semi-batch emulsion process Copolymerized with n-butyl methacrylate (BMA) to yield a poly(n-butyl methacrylate) randomly labeled with pyrene (Py-PBMA) Py-PBMA Latex

9. 9 SamplePyLMPyLM Incorporated (mol%) Particle Size (nm) PSDM w (kg/mol) Ð Py-PBMA-Latex-1PyEG 3 MA1.91181.048201.9 Py-PBMA-Latex-2PyEG 3 MA1.81201.043601.8 GPC: Py-PBMA-Latex-1

10. A film was prepared from a mixture of 5 wt% Py-PBMA-latex in 95 wt% PBMA-latex The films were dried overnight under nitrogen, then: 1.Annealed at a constant temperature 2.Rapidly cooled to room temperature on an aluminum block 3.Analysed by steady-state fluorescence 4.Steps 1 – 3 repeated for increasing annealing time 10 Film Composition FilmLatex Latex Pyrene Content (mol%) Particle Size (nm) PSD M w (kg/mol) Đ Weight Fraction 1 Py-PBMA-Latex-11.91181.048201.90.05 PBMA-Latex-10951.041,0002.00.95 2 Py-PBMA-Latex-21.81201.043601.80.05 PBMA-Latex-201191.043201.70.95

11. 11 Steady-State Fluorescence: Film 1 Annealing Time (min.) I E /I M 00.13 250.10 1100.08 5600.07 t∞t∞ 0.04 Increasing Annealing Time T an = 102 °C

12. 12 Fraction of Mixing: Film 1 119 ° C 112 ° C 111 ° C 102 ° C 94 ° C 88 ° C 84 ° C 75 ° C 98 ° C M w = 820 kg/mol

13. Fraction of Mixing: Film 2 13 88 ° C 84 ° C 75 ° C 98 ° C 94 ° C 102 ° C 111 ° C 112 ° C119 ° C M w = 360 kg/mol

14. Fraction of Mixing: Molecular Weight Dependence 14 FilmLatex Latex Pyrene Content (mol%) Particle Size (nm) PSD M w (kg/mol) Đ Weight Fraction 1 Py-PBMA-Latex-11.91181.048201.90.05 PBMA-Latex-10951.041,0002.00.95 2Py-PBMA-Latex-21.81201.043601.80.05 PBMA-Latex-201191.043201.70.95 T an = 75 °C T an = 119 °C Film 1: M w = 820 kg/mol Film 2: M w = 360 kg/mol Film 1: M w = 820 kg/mol Film 2: M w = 360 kg/mol

15. Concentration profile of molecules diffusing out of a spherical particle of radius R using Fick’s law: 3 15 Polymer Diffusion Coefficients (D) Increasing Annealing Time 3. Crank, J. The Mathematics of Diffusion, 2 nd ed. Oxford: Clarendon Press, 1975, pp 28-30. R

16. 16 Polymer Diffusion Coefficients (D)

17. Diffusion Coefficients: f m 17 Film 1: M w = 820 kg/molFilm 2: M w = 360 kg/mol

18. Apparent Activation Energy Following the procedure outlined in previous FRET studies, E a was found by comparing D at different temperatures at a fixed f m. 1,2,6-8 Using an Arrhenius type plot, E a = R·Slope 18 1. Zhao, C., Wang, Y., Hruska, Z., Winnik, M. Macromolecules 1990, 23, 4082-4087. 2.Wang, Y., Winnik, M. Macromolecules 1993, 26, 3147-3150. 6. Oh, J. K., Tomba, P., Ye, X., Eley, R., Rademacher, J., Rarwaha, R., Winnik, M. A. Macromolecules 2003, 36, 5804-5814. 7. Wang, Y. C., Winnik, M. A. J. Phys. Chem. 1993, 97, 2507 8. Ye, X., Farinha, J. P. S., Oh, J. K, Winnik, M. A., and Wu, C. Macromolecules, 2003, 36 (23), 8749–8760 fmfm MethodPy: Film 1Py: Film 2FRET 1 FRET 7 M w (kg/mol)820360420600 E a (kJ/mol)180 ± 8160 ± 21159163 Film 1: M w = 820 kg/mol Film 2: M w = 360 kg/mol fmfm fmfm PBMA Film probed by FRET M w = 420 kg/mol

19. Master Curves Using E a Master curves (left) were constructed by shifting D(T) using the E a values found in the previous slide T 0 = 75 °C 19 Comparison with a master curve (right) of a PBMA film using FRET 8 T 0 = 57 °C M w = 38 kg/mol 8. Ye, X., Farinha, J. P. S., Oh, J. K, Winnik, M. A., and Wu, C. Macromolecules, 2003, 36 (23), 8749–8760 107 °C 74 °C 56 °C 90 °C PBMA Film probed by FRET (M w = 38 kg/mol ) 8 Film 1: M w = 820 kg/mol Film 2: M w = 360 kg/mol

20. Why Use Pyrene Excimer Formation? 20 RequirementFRETPyrene Excimer Formation Instrumentation Time-resolved fluorometer (complex and expensive) Steady-state fluorometer (simple and inexpensive) Data Acquisition~ 10 minutes per decay~ 30 seconds per spectrum Fluorescence Analysis Decay must be modeled, fitted, and then integrated I E /I M ratio Fluorescently-Labeled Latex 2 (donor labeled, acceptor labeled) 1 (pyrene labeled) Film Composition100 wt% labeled-latex ≤ 5 wt% labeled-latex ≥ 95 wt% native-latex Latex NanoparticlesSymmetricalSymmetrical or Asymmetrical

21. Future Work Probe the diffusion between asymmetric latex nanoparticles: Particle size Molecular weight Different Polymers 21 Py

22. Supervisors: Prof. Jean Duhamel Prof. Mario Gauthier All members of the Duhamel and Gauthier groups. Thank you for your attention! 22Acknowledgements

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24. 24 WLF: Doolittle: Linear free volume: