1. Chemistry 367L/392N Macromolecular Chemistry Lecture 7

2. Chemistry 367L/392N Decomposition of Thermal Initiator di-tert-butylperoxideAIBNdi-tert-butylperoxalate f = 0.65f = 0.75f=0.95   I kf dt Rd d 2 R i  Efficiency factor ( f ): k d I → 2 R·

3. Chemistry 367L/392N - d[M·] Ri=Ri=Ri=Ri= dt = 2 k t [M·] 2 Where k t = k tc + k td Rp=Rp=Rp=Rp= dt -[M]-d[M]-[M]-d[M] = k p [M][M·] = k p [M][M·] [M·]= Kinetics of free radical polymerization  Steady state assumption: What is the Propagation rate ( Rp ) 2 ][2][2  MkIfk td t d kIfk][ Rp=Rp=Rp=Rp= dt -d[M] = k p [M] = k p [M] t d kIfk][So… Ri = Rt

4. Chemistry 367L/392N Average kinetic chain length ( Ӯ ) Disproportionation : Disproportionation : Combination : Combination : Kinetics of free radical polymerization Ӯ R R R R t p i p  Ӯ ][( ][ 2 ][2 ][ ][ 2 ]][[ 2 Ikfk Mk Mk Mk Mk MM K dt p t p t p       DP = 2Ӯ2Ӯ2Ӯ2Ӯ Ӯ

5. Chemistry 367L/392N The relationship between DP and conversion With termination reactions The chain growth system

6. Chemistry 367L/392N TEMPO Controlled Polymerization (2,2,6,6-tetramethylpiperidinyl-1-oxy) TEMPO 1993 M. K. Georges, R. P. N. Veregin, P. M. Kazmaier and G. K. Hamer (Xerox Corporation), "Narrow Molecular Weight Resin by Free Radical Process." (2,2,6,6-tetramethylpiperidinyl-1-oxy) TEMPO

7. Chemistry 367L/392N Radical Chain Growth Chain polymerization with termination Chain polymerization without termination e.g. nitroxide-mediated radical polymerization Life time of polymer radical chain is about 1 second Initiator slowly decomposes throughout polymerization time Steady State approximation: rate of initiation = rate of termination rate of initiation = rate of termination Therefore, [propagating radical] remains constant Therefore, [propagating radical] remains constant Initiator decomposes quickly (high temp) polymer chains have long life times “Living” DP 50 100 conversion DP 50 100 conversion

8. Chemistry 367L/392N Controlled Free Radical Polymerization

9. Chemistry 367L/392N Library of alkoxyaminesevaluated as initiators for the living free radical polymerization of styrene and n-butyl acrylate. free radical polymerization of styrene and n-butyl acrylate.

10. Chemistry 367L/392N TEMPO Acrylates???

11. Chemistry 367L/392N Published Example of Block Copolymer Formation Reversible trapping prevents irreversible termination A living poly(styrene) block heated in the presence of methyl acrylate to give diblock D

12. Chemistry 367L/392N Control of polymer Architecture

13. Chemistry 367L/392N

14. The relationship between M wt and conversion Step growth system

15. Chemistry 367L/392N The relationship between M wt and conversion With termination reactions The chain growth system

16. Chemistry 367L/392N The relationship between M wt and conversion With no termination reactions The chain growth system

17. Chemistry 367L/392N Other Controlled/Living Radical Polymerizations Nitroxide mediated stable free radicals e.g. TEMPO Atom Transfer Polymerisation Cu(I)Br/Ligand Cu(I)Br/LigandRAFTthioesters/xanthates

18. Chemistry 367L/392N K. Matyjaszewski: Macromolecules 1997, 30, p7697; 7042; 7034; 7348; 8161; 7692; 6507, 6513, 6398 JACS 1997, 119, p674 V Percec: Macromolecules 1997, 30, p6705, 8526 M Sawamoto: Macromolecules 1997, 30, p2244, 2249 Teyssie: Macromolecules 1997, 30, p7631, Haddleton: Macromolecules 1997, 30, p2190 Atom Transfer Radical Polymerization - ATRP

19. Chemistry 367L/392N Macromolecules, 30 (25), 7697 -7700, 1997. ATRP ATRP works on Acrylates !!

20. Chemistry 367L/392N Living Free-Radical Polymerization by Reversible Addition-Fragmentation Chain Transfer: The RAFT Process Macromolecules, 31 (16), 5559 -5562, 1998 Magic Reagent

21. Chemistry 367L/392N Radical addition to Dithionate esters

22. Chemistry 367L/392N RAFT Polymerisation

23. Chemistry 367L/392N Molecular weight distributions for poly(styrene-co-acrylonitrile) polymerized by heating styrene and acrylonitrile (62:38 mole ratio) at 100 C in the presence of cumyl dithiobenzoate RAFT works!!

24. Chemistry 367L/392N FRONTIERS IN POLYMER CHEMISTRY VIRGIL PERCEC, GUEST EDITOR Chemical Reviews Volume 101, Issue 12 (December 12, 2001) Colored ProductsColored Products Strange Chain endsStrange Chain ends Metal ContaminationMetal Contamination The role of Cu in ATRPThe role of Cu in ATRP Sociology and psychologySociology and psychology CRP - Issues

25. Chemistry 367L/392N Measuring Molecular Weight Alfredo Membrane Osmometry Alfredo Linda Vapor Phase Osmometry Linda Viscometry Gel Permeation Chromatography –Size exclusion Chromatography Light Scattering MALDI Others –End group analysis, etc.

26. Chemistry 367L/392N For normal (Newtonian) flow behaviour:  = (F/A) = . (dv/dy) Definition of viscosity:  /(dv/dy) units: (dyne/cm 2 )/sec -1 = dyne.sec.cm -2.. = POISE (P) At 20.0 o C,  (water) ~ 0.01P = 1.0 Centipoise shear stress shear rate viscosity

27. Chemistry 367L/392N A dissolved macromolecule will INCREASE the viscosity of a solution because it disrupts the streamlines of the flow: Viscosity of Polymer solutions:

28. Chemistry 367L/392N Ubbelohde Viscometer

29. Chemistry 367L/392N 1. “U-tube” (Ostwald or Ubbelohde) 2. “Cone & Plate” (Couette) Types of Viscometers:

30. Chemistry 367L/392N relative viscosity  r We define the relative viscosity  r as the ratio of the viscosity of the solution containing the macromolecule, , to that of the pure solvent in the absence of macromolecule,  o :  r =  o units? For a U-tube viscometer,  r = ( t/t o ). (  o ) Relative viscosity  r

31. Chemistry 367L/392N The relative viscosity depends (at a given temp.) on the concentration of macromolecules, the shape of the macromolecule & the volume it occupies. We can infer things about the shape and volume of the macromolecule if we eliminate the concentration contribution. The first step is to define the reduced viscosity  red =  r – 1)/c Where C is the concentration in gm/ml Reduced viscosity

32. Chemistry 367L/392N To eliminate non-ideality effects deriving from exclusion volume, backflow and charge effects, etc we by analogy with osmotic pressure, measure  red at a series of concentrations and extrapolate to zero concentration:  ] = Lim c ⃗ 0  red ) units [  ] = ? The Intrinsic Viscosity [  ]

33. Chemistry 367L/392N Molecular Weight from [  ] Mark-Houwink-Kuhn-Sakurada equation [  ] = K’ M a a = 1.8 a = 0 a = 0.5-0.8

34. Chemistry 367L/392N Representative Viscosity-Molecular Weight Constants a Polymer Polystyrene (atactic) c Polyethylene (low pressure) Poly(vinyl chloride) Polybutadiene 98% cis-1,4, 2% 1,2 97% trans-1,4, 3% 1,2 Polyacrylonitrile Poly(methyl methacrylate-co- styrene) 30-70 mol% 71-29 mol% Poly(ethylene terephthalate) Nylon 66 Solvent Cyclohexane Cyclihexane Benzene Decalin Benzyl alcohol Cyclohexanone Toluene DMF g DMF 1-Chlorobutane M-Cresol Temp o C 35 d 50 25 135 155.4 d 20 30 25 30 25 Molecular Weight Range  10 -4 8-42 e 4-137 e 3-61 f 3-100 e 4-35 e 7-13 f 5-50 f 5-16 f 5-27 e 3-100 f 5-55 e 4.18-81 e 0.04-1.2 f 1.4-5 f K b  10 3 80 26.9 9.52 67.7 156 13.7 30.5 29.4 16.6 39.2 17.6 24.9 0.77 240 a b 0.50 0.599 0.74 0.67 0.50 1.0 0.725 0.753 0.81 0.75 0.67 0.63 0.95 0.61 a Value taken from Ref. 4e. b See text for explanation of these constants. c Atactic d  temperature. Weight average. f Number average. g N,N-dimethylformamide.