PolymerizationPolymerization ““LivingLiving””/Controlled/Controlled PolymerizationPolymerization PolymerizationPolymerization forfor NanotechnologyNanotechnology 중합반응에중합반응에 관한 관한 소개 소개 (나노기술과(나노기술과 관련 관련 있는 있는 중합 중합 방법) 방법)

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PolymersPolymers withwith ControlledControlled ArchitecturesArchitectures

Many Natural Polymeric Materials Å Perfect Monodisperse Macromolecules Successive condensation of monomers with polymer end-groups activated by enzymes

“Living”/Controlled Polymerization Radical, Cationic, Anionic, ROMP, Coordination Synthetic Polymeric Materials (via Chain-Growth Polycondensation) with Controlled Architecture Dendritic Macromolecules & Linear Oligomers (Stepwise synthesis via Step-Growth Condensation)

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1 Dendrimers

Commercially Available Dendrimers

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Synthesis of Dendrimers

DSM’s Poly(propylene imine) Dendrimer (Fifth Generation – 64 primary amine Group)

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2 Well-Defined Dendrimers

Frechet J. M. J. et al. Chem. Rev. 2001, 101, 3855.

Well-Defined (Monodisperse & Controlled)

Branched vs. Linear & Folded

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“Living”/Controlled“Living”/Controlled PolymerizationPolymerization vs.vs.Step-GrowthStep-Growth PolymerizationPolymerization

“Living”/Controlled Polymerization

DP = [M]0/[I]0 PDI ≅ 1 Step-Growth Polymerization

DP = 1/(1-p) Molecular Weight (DP) Control of Molecular Weight chain DPn = (1+r)/(1-r), if p = 1 r = [A]/[B], p = conversion

Mn living Mw/Mn = 1+p If p = 1, PDI = 2 Conversion step 0100%conversion 6/32

3 Types of Chain Polymerizations of Various Unsaturated Monomers Types of Initiation Monomers Radical Cationic Anionic Ethylene + - + 1-Alkyl olefins (α-olefins)--- 1,1-Dialkyl olefins - + - 1,3-Dienes + + + Styrene, α-methyl styrene + + + Halogenated olefins + - -

Vinyl esters (CH2=CHOCOR) + - - Acrylates, methacrylates + - + Acrylonitrile, methacrylonitrile + - + Acrylamide, methacrylamide + - + Vinyl ethers - + - N-Vinyl carbazole + + - N-Vinyl pyrrolidone + + - Aldehydes, ketones - + +

Exceptions: Z-N OR (CH2)nH α-olefins 1,1-dialkyl olefins vinyl ethers O O CH2 C OCH2CH2 Ring Opening: n O 7/32

Living Polymerization (LP) vs. Controlled Polymerization (CP)

Living Polymerization and Polydispersity Æ Weak Correlation

a. Chain-breaking reactions: increase of DPw/DPn with increasing DPn and conversion b. Slow initiation and slow exchange: decrease DPw/DPn and DPn with increasing conversion c. Polydispersity alone is a poor criterion for judging the living character of a polymerization

1. Living polymerizations can have DPw/DPn > 2 (slow exchange) 2. Polymers with DPw/DPn < 1.1 can have 50% terminated chain ends

LP LP & CP CP

Living Polymerization: Controlled Polymerization: Chain growth Chain or Step growth No chain breaking (no transfer/termination) Limited chain breaking possible - slow initiation possible - fast initiation - slow exchange possible - fast exchange - uncontrolled molecular weights possible - controlled molecular weights - high polydispersities possible - low polydispersities

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4 Experimental Evaluation of “Living”/Controlled System

Necessarily, Rtr = Rt = 0 (a truly living system) Ideally, Ri ≥ Rp, Rexch ≥ Rp, propagation is irreversible When these conditions hold, the following can be used to experimentally evaluate the livingness of a polymerization:

DPw/DPn ~ 1 + 1/DPn DP [M]0 w ln Mn [M] DPn

time conversion (%) conversion (DPn)

Real Systems Overall Effecta

Kinetic characteristic on Rp on Mn/Mn, th on DPw slow initiation (rel. to propagation)

slow exchange (rel. to propagation)

transfer ( to anything other than polymer)

termination

a = increase; = decrease; = unaffected 9/32

Conventional vs. Controlled (Radical Polymerization)

¾ Conventional Radical Polymerization

kd I 2 R TT ~ ~ 8080 ±± 2020ooCC ki R + M P1 -5-5 -1-1 M /M > 1.5 kkdd~~ 1010 ss n w n M kp kk ~~ 101033 ±±11 MM-1-1ss-1-1 P1 + M Pn+1 pp kk ~~ 101077±±11 MM-1-1ss-1-1 kt H = tt Pn + Pm Pn + Pm

0 0.2 0.4 0.6 0.8 1 Conversion ¾ “Living”/Controlled Radical Polymerization

ka R X R + X kd oo M /M < 1.5 TT ~ ~ 120120 ±± 2020 CC w n k 00 ±±22 -1-1 R M i P kk ~~ 1010 ss + 1 aa n k 88 ±±11 -1-1 M = [M] /[I] p kkd ~~ 1010 ss o o P1 + M Pn+1 d 44 ±±11 -1-1 -1-1 kt H = kkpp~~ 1010 MM ss Pn + Pm P + P n m 77±±11 -1-1 -1-1 kktt~~ 1010 MM ss ka 0 0.2 0.4 0.6 0.8 1 Pn X Pn + X Conversion kd

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5 Controlling Radical Polymerizations a. The problem with conventional radical polymerizations: 7 -1 -1 1. diffusion-controlled termination (kt = 10 M s ) 2 termination is bimolecular: Rt = kt [M •] b. The solution: keep [M •] low through slow initiation: 2. slow initiation -5 -1 -1 -2 Ri = 2 f kd [I] (kd = 10 M s ; [I]0 = 10 M)

Therefore, high polymer is still possible in spite of the high termination rate constant because of slow initiation and termination rate (WARNING! rate ≠ rate constant!).

c. Designing a Controlled Radical Polymerization - HOW?

1. By definition, Ri ≥ Rp and [I]0 = concentration of propagating chains. 2. Additionally, for any controlled polymerization:

Δ [M] [M]0 DPn ==(at full conversion) [I]0 [I]0 -2 consider full conversion for DPn = 1000; [M]0 = 10 M; [I]0 = 10 M.

3. However, from the definition of DPn :

R p kp [M] [M ] kp [M] DP = = n R 2 = t kt [M ] kt [M ] and:

kp [M] [M ] = kt DPn (instantaneous concentration of radicals) 2 -1 -1 7 -1 -1 -7 for DPn = 1000; [M]0 = 10 M; kp = 10 M s ; kt = 10 M s ; [M •] = 10 M 11/32

Control of Radical Polymerization

• Extending life of propagating chains (from <1s to >1 h) (similar rates?)

• Enabling quantitative initiation (From Ri << Rp to Ri >> Rp)

• Controlling DPn (D[M]/[I]o), MWD, Functionality, Composition, Topology • BY EQUILIBRIA BETWEEN RADICALS AND DORMANT SPECIES

kact ¾ Reversible deactivation by coupling Pn-T Pn* + T* kdeact – Nitroxide-mediated polymerization kp Monomer

¾ Reversible deactivation by atom transfer kact n n+1 Pn-X + Mt /L Pn* + X-Mt /L – ATRP kdeact kp ¾ Degenerative transfer Monomer

– Alkyl iodides ktr Pn* + Pm-X Pn-X + Pm* – Unsaturated polymethacrylates (CCT) k-tr k – Dithioesters (RAFT) p kp Monomer Monomer

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6 RAFT: Reversible Addition Fragmentation Chain Transfer

CH3 CH3 S R CH3 CH3 S k R CH2 C CH2 C* SC a CH2 C CH2 C S C* CO CH CO CH Z 2 3 2 3 k-a Z CO2CH3 CO2CH3 kp M

kβ ƒ Monomers: Styrenes, (Meth)acrylates,

Acrylic acid, Vinyl Benzoate, DMAEMA, etc CH3 CH3 S *R ƒ Transfer Agents: Dithioesters CH2 C CH2 C SC kp Z ƒ Initiators: AIBN, BPO CO2CH3 CO2CH3 M ƒ [M]: bulk, solution Mn Mw/Mn -1 -2 ƒ [TA] : 10 to 10 M expt Limit < 1.1 o Mn ƒ [In] /[TA] : 0.1 to 0.6 -2 o o kp/kex < 10 ƒ Temp: 60-150 oC M theo ƒ Time: 2-20 hours n

ƒ Blocks: possible but limits Conversion Conversion

Moad, G.; Rizzardo, E. et. al. Macromolecules 1998, 31, 5559; 1999, 33, 2071 Le, T.P.; Moad, G.; Rizzardo, E.; Thang, S.H. PCT Int. Appl. WO 9801478 A1 980115. 13/32

Nitroxide/TEMPO Polymerization NO* O P EtO OEt H H kact H *O N CH2 C CH2 C O N CH2 C CH2 CH* Tordo, P.; Gnanou,Y. kdeact ACS Symp. Ser. 1998 685, 225. C6H5 C6H5 C6H5 C6H5

kp R M ƒ Monomers: Styrenes & comonomers N O* ƒ Initiators: Alkoxyamines or -> Acrylates & Lower Temp Ph BPO/Nitroxides Additives & New Nitroxides Hawker, C. et al ƒ [M]: bulk (Acids, Dicumyl peroxides) JACS 1999, 121, 3904. -1 -2 ƒ [In]o: 10 to 10 M M /M o ln(Mo/M) Mn w n ƒ Temp: 120-140 C Limit ~ 1.1 M expt ƒ Time: >10 hours n

• Self initiation dominates R theo p Mn -11 • kact/kdeact ~ 10 M • Side reactions Time Conversion Conversion (H-abstraction by TEMPO) Solomon,D.H.,. et al. U.S. Patent, 1986 4,581,429. Georges, M.K., et al. Macromolecules 1993 26, 2987. 14/32

7 ATRP: Atom Transfer Radical Polymerization

H H kact H n n+1 CH2 C CH2 C X + Mt Y/L CH2 C CH2 CH* + X-Mt Y/L kdeact R R R R

kp ƒ Monomers: Styrenes , (Meth)acrylates, AN, ... M ƒ Initiators: Alkyl halides or AIBN/XMtn+1/L • Rate =f(K, [RX], [Mtn], [XMtn+1]) ƒ Mt: Cu, Fe, Ru, Ni, Pd, Rh,… -9 -6 • kact/kdeact = 10 to 10 M ƒ L: Bpy, amines, phosphines,… • Side reactions ƒ X: Cl, Br, I, SCN,… – potential redox of radicals ƒ [M]: bulk, solution, emulsion, suspension, – C-Mt bonding disp. M /M -2 ln(Mo/M) Mn w n ƒ [In]o: 1 to 10 M expt Limit ~ 1.1 ƒ Temp: 20-140 oC Mn ƒ Time: 1 to 10 hours theo Mn

Time Conversion Conversion Sawamoto, M.,. et al. Macromolecules 1995 28, 1721. Matyjaszewski, K., et al. JACS 1995 117, 5614. 15/32

Component for ATRP

-1 -1 ka ~ 1 M s X n n+1 + Mt /Ligand + X Mt /Ligand 7 -1 -1 Y kda ~ 10 M s Y M kp ƒ Y should stabilize radical by resonance/inductive effects. – Can be: -Phenyl, Carbonyl, Ester, Cyano, Multiple halogens. ƒ X must rapidly exchange between Mtn/L & chain end

– Generally a halogen (Cl, Br, I), can be pseudo-halogen (-SCN, -N3) n ƒ Mt /Ligand should allow selective & fast exchange. n –Mt : Cu, Ru, Ni, Fe, Pd, etc.; preferred 1 el. redox – Ligand: adjusts equilibrium, solubilizes metal, assures selectivity. • Bipyridines, functionalized pyridines, linear & branched amines, cyclic amines, phosphines, phosphites, carboxylates, phenoxides, etc. ƒ Temp., Solvent & Counterion: affect equilibrium, rates & selectivity. Æ Structure-Reactivity Correlation for: R(Y), X, M, Mt, L, S, T, etc. Æ Precise structure of catalysts, active and dormant species 16/32

8 How ATRP Works: Styrene, CuBr/dNbpy, 110 oC

R' R-R 8 -1 -1 + R' + kt< 10 M s R' R' R X N -1 -1 N N ka =0.45 M s N Cu H3C Br + R + X Cu N N k =1.1 107 M-1s-1 N d M R' N R' 3 -1 -1 R' kp=1.6 10 M s R' Frequency of molecular events at chain end; τ =1/(k [C]) Concentrations: [M] =5 M – activation: τ = 22 s [R-Br] = 10-1 M – propagation: τ = 0.12 ms [CuIBr/2dNbpy] = 10-1 M [CuIIBr /2dNbpy] = 5X10-3 M – deactivation: τ = 0.018 ms (6 times faster than propagation !!!) 2 [P*] » 1X10-7 M – termination: τ = 0.1 s ( i.e. 800 times slower than propagation !) Æ Chain wakes up every 20 s, adds monomer only every 120 s (2 min; i.e. 3 h needed for DP=100) & dies after 100,000s (30 h) cf> In the case of MA, CuBr/PMDETA, 90 oC, chain wakes up every 330 s (5 min), adds 14 monomer units, goes back to sleep for 5 min & dies after 100 days.

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Ligands Used in Copper-Mediated ATRP

CF 3 F3C F2CCF2 CF 2 F2C F2C CF 2 CF 2 F2C F2C CF 2 CF F C 2 2 Me O2CCO2Me

NN NN NN NN NN NN NN

NN H O N C8H17 NN NNCH NN NNC8H17 NHNC8H17 N N 8 17 N N NN C H NN 7 15

O NN NN N H C C H H C NNCH NN H2NN 17 8 8 17 17 8 8 17 NN NN NN

O O NN NN NN NH HN N N NN N N N N N N N N N N N

R C H C H O O 8 17 18 37 N N RR N N N N N N NN NN N N NH HN NN NN NN N N H17C8 C8H17 H17C8 C8H17

N N C8H17 N N NN NN N N N N N N N NR N N O R N NN NN N R N N N N N N N N N N N R O R O O N N N N N N R N N N N NN N N N N N R' = -CH2CH2COOR" O N N R N N N N N N R O R R' = -CH2CH2COOR" C H 8 17 N N SciFinderN Scholar, March 30, 2002; out of total 1623 N H B NN NH N N N N N HO OH N N OH NH N

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9 Nano-StructuredNano-Structured MaterialsMaterials viavia ATRPATRP

Matyjaszewski K. et al. Chem. Rev. 2001, 101, 2921. Chem. Mater. 2001, 13, 3436. Adv. Mater. 1998, 10, 901. Prog. Polym. Sci. 2001, 26, 337. 19/32

Comparison of Various CRP Systems

¾ ATRP + Especially well suited for LMW functional oligomers ($, rates) + May be useful for difficult block copolymers + Very good for hybrids and transformations + Easy to incorporate end/side functionalities - Catalyst should be removed/recycled ¾ RAFT + Easy for various homopolymers + May be unique for difficult monomers and HMW blocks - Control of EG limited by % of decomposed initiator, Retardation for LMW, Stars and More complex architectures? - New, more friendly transfer agents needed ($$, smell, color, removal) ¾ SFRP, NITROXIDES + no metal present + alkoxyamines may act as stabilizers - $, limited range of monomers for TEMPO - very difficult for MMA even with new nitroxides

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10 Comparative Advantages of CRPs

LMW 3 2.5 Hybrids 2 End Funct ATRP 1.5 1 NMP 0.5 RAFT Env 0 Blocks

Water Mon Range

HMW

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Constituents of CRP/ATRP: Mechanisms, Processes, Materials

Chemistry Mechanisms: - Catalyst Structure -1. -1 N N N ka ~ 1 M s - Ligand Design + Cu P + N Pn Br 7 -1. -1 n Br Cu - Model Kinetics kd ~ 10 M s N NN + M N - Polymerization - Modeling 3 -1. -1 kp ~10 M s ATRP Pn-Pm Processes: Materials - Catalyst Optimization - Catalyst Recycling X xx x x x X Block Copolymers x x x X - Monomer Range x x x x X Y x - Functional Initiators x x X X Gradient Molecular Hyperbranched / Functional Modified Surfaces - Reaction Media Copolymers Multifunctional Brushes Colloids - Reaction Conditions

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11 CRP Controls Molecular & Nanostructures

block copolymer homopolymer periodic copolymer

random copolymer tapered / gradient copolymer graft copolymer

x xxx x x Pre-assembly linear side-functional groups

Composition & X Microstucture end- functional polymers star (& TACTICITY!) XX Self-assembly X Y telechelic polymers comb / brush

Topology site-specific functional polymers network/ crosslinked macromonomers

X X X X X X X Functionality X X X X X dendritic / X Y X hyperbranched multifunctional Bates & Fredrickson, 1999 23/32

Block and Graft Copolymer Morphology

Driving Forces:

1. Minimize domain surface area/domain volume ratio

2. Limited by localization of junction between segments at domain boundary

3. Entropic limitation - maintain uniform density

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12 1000

500 -3 Spheres of B Spheres of S Cylinders of B Cylinders of S 100 Lamellae

50 Molecular weight x 10

Homogeneous

0.0 0.2 0.4 0.6 0.8 1.0 Weight fraction of S 25/32

A A OBDD A,B OBDD B B Spheres Cylinders Lamellae Cylinders Spheres Increasing volume fraction of A Phase

Schematic representation of the equilibrium domain morphology in AB block copolymers as a function of copolymer composition. Included are the BCC lattice structure of spherical microdomains and the ordered bicontinuous double diamond (OBDD) structure. polyisoprene

p o l y OBDD computer image s t y r e n e

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13 poly- poly- polybutadiene styrene styrene 10-50,000 MW 10-50,000 MW 50-70,000 MW

poly- styrene poly- styrene

poly- styrene poly- styrene

1000 Å 27/32

(a) (b) (c) (d) (e)

0.5 μm

< 15 % 15-35% 35-65% 65-85% > 85%

Morphological changes brought about by increasing the polystyrene content of an AB poly(styrene-b-butadiene) copolymer. Schematic diagrams are shown above the electron micrographs and indicate (a) PSt spheres in a PBd matrix, (b) PSt cylinders in a PBd matrix, (c) lamellae, (d) PBd cylinders in a PSt matrix, and (e) PBd spheres in a PSt matrix (Angew. Chem. Int. Ed. , 1979, 18, 287).

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14 “Knitting with Block Copolymers” ABC triblock copolymer of poly(styrene)-b-poly(isoprene)-b-poly(methyl methacrylate) Cover of “Physics Today”, 1999 29/32

Block Copolymers Methods of Synthesis of Block Copolymers

1. Block Copolymers by Anionic Living Polymerization Techniques 2. Block Copolymers by Cationic Polymerization 3. Block Copolymers by Coupling Reactions between Preformed Functional Blocks 4. Block Copolymers by Coordination Polymerization 5. Block Copolymers by Conventional Free Radical Copolymerization Techniques 6. Block Copolymers by Controlled Radical Copolymerization Techniques 7. Block Copolymers by Site Transformation Techniques 8. Block Copolymers by Step-Growth Procedure Types of Block Copolymers AB diblock ABA triblock BABtriblock

AB ABA B A B

ABC triblock multiblock -(AB)-n multiblock ABCBA A BC AB AB C B A n

star (AB)3 star (AB)6

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15 Graft Copolymers

Types of Graft Copolymers

Homopolymer in the backbone, different (co)polymer grafts

poly(A) poly(A) poly(A)

poly(B) poly(B) poly(B,C)

poly(C)

Copolymer in the backbone, homopolymer grafts

poly(A,B) poly(A) poly(B)

poly(C) poly(C)

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Methods of Synthesis of Graft Copolymers

1. “Grafting from” Methods

2. “Grafting onto” Methods

3. Graft Copolymer Synthesis via Macromonomers (“Grafting through”)

4. Graft Copolymers by Free Radical Grafting Techniques

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