DOCSLIB.ORG

Polymerization

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Polymerization PolymerizationPolymerization ““LivingLiving””/Controlled/Controlled PolymerizationPolymerization PolymerizationPolymerization forfor NanotechnologyNanotechnology 중합반응에중합반응에 관한 관한 소개 소개 (나노기술과(나노기술과 관련 관련 있는 있는 중합 중합 방법) 방법) 1/32 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) 2/32 1 Dendrimers Commercially Available Dendrimers 3/32 Synthesis of Dendrimers DSM’s Poly(propylene imine) Dendrimer (Fifth Generation – 64 primary amine Group) 4/32 2 Well-Defined Dendrimers Frechet J. M. J. et al. Chem. Rev. 2001, 101, 3855. Well-Defined (Monodisperse & Controlled) Branched vs. Linear & Folded 5/32 “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 8/32 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 10/32 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 12/32 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 Monomers: Styrenes, (Meth)acrylates, Acrylic acid, Vinyl Benzoate, DMAEMA, etc CH3 CH3 S *R Transfer Agents: Dithioesters CH2 C CH2 C SC kp Z Initiators: AIBN, BPO CO2CH3 CO2CH3 M [M]: bulk, solution Mn Mw/Mn -1 -2 [TA] : 10 to 10 M expt Limit < 1.1 o Mn [In] /[TA] : 0.1 to 0.6 -2 o o kp/kex < 10 Temp: 60-150 oC M theo Time: 2-20 hours n 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 Monomers: Styrenes & comonomers N O* Initiators: Alkoxyamines or -> Acrylates & Lower Temp Ph BPO/Nitroxides Additives & New Nitroxides Hawker, C. et al [M]: bulk (Acids, Dicumyl peroxides) JACS 1999, 121, 3904. -1 -2 [In]o: 10 to 10 M M /M o ln(Mo/M) Mn w n Temp: 120-140 C Limit ~ 1.1 M expt 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 Monomers: Styrenes , (Meth)acrylates, AN, ... M Initiators: Alkyl halides or AIBN/XMtn+1/L • Rate =f(K, [RX], [Mtn], [XMtn+1]) Mt: Cu, Fe, Ru, Ni, Pd, Rh,… -9 -6 • kact/kdeact = 10 to 10 M L: Bpy, amines, phosphines,… • Side reactions X: Cl, Br, I, SCN,… – potential redox of radicals [M]: bulk, solution, emulsion, suspension, – C-Mt bonding disp. M /M -2 ln(Mo/M) Mn w n [In]o: 1 to 10 M expt Limit ~ 1.1 Temp: 20-140 oC Mn 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 Y should stabilize radical by resonance/inductive effects. – Can be: -Phenyl, Carbonyl, Ester, Cyano, Multiple halogens. X must rapidly exchange between Mtn/L & chain end – Generally a halogen (Cl, Br, I), can be pseudo-halogen (-SCN, -N3) n 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. 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.
Load more

Recommended publications
  • Cationic/Anionic/Living Polymerizationspolymerizations Objectives
    Chemical Engineering 160/260 Polymer Science and Engineering LectureLecture 1919 -- Cationic/Anionic/LivingCationic/Anionic/Living PolymerizationsPolymerizations Objectives • To compare and contrast cationic and anionic mechanisms for polymerization, with reference to free radical polymerization as the most common route to high polymer. • To emphasize the importance of stabilization of the charged reactive center on the growing chain. • To develop expressions for the average degree of polymerization and molecular weight distribution for anionic polymerization. • To introduce the concept of a “living” polymerization. • To emphasize the utility of anionic and living polymerizations in the synthesis of block copolymers. Effect of Substituents on Chain Mechanism Monomer Radical Anionic Cationic Hetero. Ethylene + - + + Propylene - - - + 1-Butene - - - + Isobutene - - + - 1,3-Butadiene + + - + Isoprene + + - + Styrene + + + + Vinyl chloride + - - + Acrylonitrile + + - + Methacrylate + + - + esters • Almost all substituents allow resonance delocalization. • Electron-withdrawing substituents lead to anionic mechanism. • Electron-donating substituents lead to cationic mechanism. Overview of Ionic Polymerization: Selectivity • Ionic polymerizations are more selective than radical processes due to strict requirements for stabilization of ionic propagating species. Cationic: limited to monomers with electron- donating groups R1 | RO- _ CH =CH- CH =C 2 2 | R2 Anionic: limited to monomers with electron- withdrawing groups O O || || _ -C≡N -C-OR -C- Overview of Ionic Chain Polymerization: Counterions • A counterion is present in both anionic and cationic polymerizations, yielding ion pairs, not free ions. Cationic:~~~C+(X-) Anionic: ~~~C-(M+) • There will be similar effects of counterion and solvent on the rate, stereochemistry, and copolymerization for both cationic and anionic polymerization. • Formation of relatively stable ions is necessary in order to have reasonable lifetimes for propagation.
    [Show full text]
  • High Temperature, Living Polymerization of Ethylene by a Sterically-Demanding Nickel(II) Α-Diimine Catalyst
    polymers Article High Temperature, Living Polymerization of Ethylene by a Sterically-Demanding Nickel(II) α-Diimine Catalyst Lauren A. Brown, W. Curtis Anderson Jr., Nolan E. Mitchell, Kevin R. Gmernicki and Brian K. Long * ID Department of Chemistry, University of Tennessee, Knoxville, TN 37996, USA; [email protected] (L.A.B.); [email protected] (W.C.A.J.); [email protected] (N.E.M.); [email protected] (K.R.G.) * Correspondence: [email protected]; Tel.: +1-865-974-5664 Received: 15 December 2017; Accepted: 27 December 2017; Published: 2 January 2018 Abstract: Catalysts that employ late transition-metals, namely Ni and Pd, have been extensively studied for olefin polymerizations, co-polymerizations, and for the synthesis of advanced polymeric structures, such as block co-polymers. Unfortunately, many of these catalysts often exhibit poor thermal stability and/or non-living polymerization behavior that limits their ability to access tailored polymer structures. Due to this, the development of catalysts that display controlled/living behavior at elevated temperatures is vital. In this manuscript, we describe a Ni α-diimine complex that is capable of polymerizing ethylene in a living manner at temperatures as high as 75 ◦C, which is one of the highest temperatures reported for the living polymerization of ethylene by a late transition metal-based catalyst. Furthermore, we will demonstrate that this catalyst’s living behavior is not dependent on the presence of monomer, and that it can be exploited to access polyethylene-based block co-polymers. Keywords: polyethylene; living polymerization; nickel α-diimine; catalysis 1. Introduction Controlled/living polymerizations offer a precise means by which polymer structure, co-monomer incorporation levels, and even regio- and stereoselectivity can be tailored [1–7].
    [Show full text]
  • Synthesis of Polypeptides by Ring-Opening Polymerization of A-Amino Acid N-Carboxyanhydrides
    Top Curr Chem (2011) DOI: 10.1007/128_2011_173 # Springer-Verlag Berlin Heidelberg 2011 Synthesis of Polypeptides by Ring-Opening Polymerization of a-Amino Acid N-Carboxyanhydrides Jianjun Cheng and Timothy J. Deming Abstract This chapter summarizes methods for the synthesis of polypeptides by ring-opening polymerization. Traditional and recently improved methods used to polymerize a-amino acid N-carboxyanhydrides (NCAs) for the synthesis of homo- polypeptides are described. Use of these methods and strategies for the preparation of block copolypeptides and side-chain-functionalized polypeptides are also pre- sented, as well as an analysis of the synthetic scope of different approaches. Finally, issues relating to obtaining highly functional polypeptides in pure form are detailed. Keywords Amino acid Á Block copolymer Á N-Carboxyanhydride Á Polymerization Á Polypeptide Contents 1 Introduction 2 Polypeptide Synthesis Using NCAs 2.1 Conventional Methods 2.2 Transition Metal Initiators 2.3 Recent Developments 3 Copolypeptide and Functional Polypeptide Synthesis via NCA Polymerization 3.1 Block Copolypeptides 3.2 Side-Chain-Functionalized Polypeptides 4 Polypeptide Deprotection and Purification 5 Conclusions and Future Prospects References J. Cheng Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, IL 61801, USA T.J. Deming (*) Department of Bioengineering, University of California, Los Angeles, CA 90095, USA e-mail: [email protected] J. Cheng and T.J. Deming Abbreviations AM Activated
    [Show full text]
  • Extremely Narrow-Dispersed High Molecular Weight Polyethylene
    Published on Web 09/12/2008 Extremely Narrow-Dispersed High Molecular Weight Polyethylene from Living Polymerization at Elevated Temperatures with o-F Substituted Ti Enolatoimines Sze-Man Yu and Stefan Mecking* UniVersity of Konstanz, Chair of Chemical Materials Science, Department of Chemistry, UniVersita¨tsstr. 10, D-78457 Konstanz, Germany Received July 9, 2008; E-mail: [email protected] Living polymerization techniques are an essential tool for the synthesis of polymers with controlled architectures, such as monodisperse polymers or blockcopolymers.1 Polymerization in a living fashion requires the essential absence of chain termination and irreversible transfer. In olefin polymerization, chain transfer (occurring by -hydride transfer or transfer to cocatalyst) and termination can be suppressed by polymerization at low tempera- tures.2 This, however, results in low catalyst activities and limited molecular weights attainable especially for semicrystalline polymers. Therefore, considerable effort has been directed at the development of new catalysts. Albeit a significant number of catalyst systems with living polymerization characteristics at ambient or elevated temperature have been reported,3-10 the synthesis of linear polyethylene (PE) with a high molecular weight and truly narrow Figure 1. ORTEP plot of the molecular structure of 3a. Ellipsoids are distribution remains a challenge. shown with 50% probability. The H-atoms are not shown for clarity. Phenoxyimine Ti complexes with o-fluorine substitution of the Scheme 1. Synthesis of Complexes 3a and 3b N-aryl moiety, discovered by Fujita et al., are highly active versatile catalysts for, e.g., the synthesis of narrowly distributed (ultra high molecular weight) PE and of block copolymers.3 The o-F substit- uents have been suggested to suppress chain transfer by interaction with the -hydrogen atoms of the growing PE chain.3,11 At 25 °C linear PE with Mw/Mn as low as 1.05 was obtained, when a short reaction time (3 min) and diluted ethylene (0.04 atm) were employed for this very reactive system.
    [Show full text]
  • Radical Polymerizations II Special Cases
    Radical Polymerizations II Special Cases Devon A. Shipp Department of Chemistry, & Center for Advanced Materials Processing Clarkson University Potsdam, NY 13699-5810 Tel. (315) 268-2393, Fax (315) 268-6610 [email protected] 46 © Copyright 2016 Devon A. Shipp Living Polymerizations • Objectives • Requirements – Initiation must be fast – Continuous chain • Ri >> Rp growth – Termination must be – No termination eliminated • Or at least reduced to – Well-defined chains insignificance • Chain structure • Chain length • Problems with free • Molecular weight radical polymerization distribution – Initiation is slow • Block copolymer – Radical-radical synthesis termination is fast 47 Reversible-Deactivation Radical Polymerizations (RDRP) • Often called living radical polymerization activation Dormant polymer Active polymer radical + capping group deactivation Monomer (Propagation) t P h o g l i y e Δ[M] Monomer repeat unit Functional terminal d DP = i W s ( ω ) end ("capping") group [In] r 0 p a e l r u s c X i t e y In l n o M Y Y < 1.5 Initiator ( α ) end 48 % Monomer Conversion Features of Living Polymerizations • Linear increase in • Low polydispersity molecular weight – Mw/Mn < 1.5 (often ~ 1.1) – Vs. monomer conversion • First-order monomer • Pre-defined molecular consumption weight – Same as conventional radical polymerization – DPn = Mn/FWM = Δ[M] / [Initiator] 49 Terminology/Tests for Living Polymerization • Controversy over terminology – Controlled, living, pseudo-living, quasi-living, living/controlled, living/controlled, reversible-deactivation,… • IUPAC definition of living polymerization: – Absence of irreversible transfer and termination • Cannot be applied to any radical polymerization! • Some tests for RDRP: – Continued chain growth after addition monomer added – Molecular weight increases linearly with conversion – Active species (i.e.
    [Show full text]
  • Oct 15, Controlled Polymerizations by Ki-Young Yoon
    Wednesday Meeting Controlled Polymerizations 10/15/2014 Ki-Young Yoon Organometallics : A Friend of Total Synthesis Total Synthesis Organometallics e.g. Barry Trost Organometallics : A Friend of Polymer Synthesis Organometallics Polymer Synthesis e.g. Bob Grubbs Organometallics : Still Blue Ocean Area Total Synthesis Organometallics Polymer Synthesis In theory, every organometallic reaction can branch out into polymerization Organometallics : Still Blue Ocean Area Hydrolytic kinetic resolution E. Jacobson Science 1997, 277, 936 J. Coates J. Am. Chem. Soc 2008, 130, 17658 Enantioselective Polymerization of Epoxides: the first person who borrows Jacobson’s catalyst for the polymerization Enantioselective Polymerization of Epoxides: Catalyst which Jacobson should have used for the polymerization 10 years ago Contents 1. Polymerization Mechanism o Step-growth polymerization o Chain-growth polymerization o Step-growth vs. Chain-growth 2. Efforts to turn Step-growth polymerization into Chain-growth polymerization o GRIM polymerization o Pd-catalyzed chain-growth polymerization Polymer is a mixture Polymer is not a pure substance. It is a mixture Organic reaction Single pure product Polymerization mixture Molecular Weight Distribution Irresponsible polymer chemist Average Molecular Weight mixture - Mn, Mw, PDI (=Mw/Mn) Polymer molecular weight Number Average Molecular Weight, Mn Danny’s Credit Grade Credit*Gr ade PhysOrg 3 4.0 (A) 12 Calculus 2 3.0 (B) 6 Weight Average Molecular Weight, Mw History 1 2.0 (C) 2 Mn (4.0+3.0+2.0) =3 SEC/3 trace
    [Show full text]
  • Simulating Thermodynamics and Kinetics of Living Polymerization
    SIMULATING THERMODYNAMICS AND KINETICS OF LIVING POLYMERIZATION A Thesis Presented to The Academic Faculty by Yanping Qin In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Chemistry and Biochemistry Georgia Institute of Technology August 2007 SIMULATING THERMODYNAMICS AND KINETICS OF LIVING POLYMERIZATION Approved by: Dr. Rigoberto Hernandez, Adviser Dr. C. David Sherrill School of Chemistry and Biochemistry School of Chemistry and Biochemistry Georgia Institute of Technology Georgia Institute of Technology Dr. Jean-Luc Br´edas Dr. Peter J. Ludovice School of Chemistry and Biochemistry School of Chemical and Biomolecular Georgia Institute of Technology Engineering Georgia Institute of Technology Dr. Robert M. Dickson Date Approved: July 3, 2007 School of Chemistry and Biochemistry Georgia Institute of Technology ACKNOWLEDGEMENTS I would like to begin by expressing my sincerest thanks to my advisor, Professor Rigoberto Hernandez for his consistent support and guidance throughout my graduate studies. His guidance has been invaluable over the years. I would also like to thank Professor Jean- Luc Br´edas, Professor Robert M. Dickson, Professor C. David Sherill and Professor Pete Ludovice for having served on my thesis committee and for their comments and suggestions. Thanks also goes to Dr.Alexander Popov for many insightful discussions from which I learned a lot, and my group members for their friendship. I would like to thank my parents and brother, who have been giving me love and encouragement during my hard working time. I would like to thank my husband, Jie Zheng, who supported my research and gave me strength to move forward and finish my graduate work at Georgia Tech.
    [Show full text]
  • Nonlinear Polymeric Architectures Via Olefin Metathesis
    CHAPTER 1 Introduction to Olefin Metathesis and Its Applications in Polymer Synthesis 2 Olefin Metathesis Olefin metathesis is a metal-catalyzed transformation, which acts on carbon- carbon double bonds and rearranges them via cleavage and reassembly.1-5 While the reaction itself was discovered in the mid-1950s, its now generally accepted mechanism was not proposed until 1971. 6 According to this mechanism, first introduced by Chauvin, the coordination of an olefin to a metal carbene catalytic species leads to the reversible formation of a metallacyclobutane (Scheme 1.1). This intermediate then proceeds by cycloreversion via either of the two possible paths: 1) non-productive—resulting in the re-formation of the starting materials or 2) product-forming—yielding an olefin that has exchanged a carbon with the catalyst’s alkylidene. Since all of these processes are fully reversible (Scheme 1.1), only statistical mixtures of starting materials as well as all of possible rearrangement products are produced in the absence of thermodynamic driving forces. Scheme 1.1. General mechanism of olefin metathesis. 6 Fortunately for the organic and polymer chemistry communities, the olefin metathesis reaction’s thermodynamic equilibrium can be easily influenced. There are two major approaches that are commonly employed to drive the reaction towards the desired products. One tactic is to rely on Le Chatelier’s principle by continuously removing one of the products from the reaction system in order to shift the equilibrium in favor of the other product. This method is especially effective in the case of cross metathesis (CM) 7 reactions involving terminal olefins, ring-closing metathesis (RCM) 8,9 and acyclic diene metathesis polymerization (ADMET),10-14 because the volatile ethylene gas by-product formed in these processes can be easily removed (Scheme 1.2).
    [Show full text]
  • Living/Controlled Radical Polymerizations in Dispersed Phase Systems
    Prog. Polym. Sci. 27 *2002) 1039±1067 www.elsevier.com/locate/ppolysci Living/controlled radical polymerizations in dispersed phase systems Michael F. Cunningham* Department of Chemical Engineering, Queen's University, Kingston, Ont., Canada K7L 3N6 Received 5 November 2001; revised 25 January 2002; accepted 28 January 2002 Abstract Living/controlled radical polymerization provides a route to synthesizing materials with designed microstruc- ture and narrow molecular weight distributions. A variety of living radical systems have been developed in recent years, and are based on either reversible termination *SFRP, ATRP) or reversible transfer mechanisms *RAFT, degenerative transfer). Application of living radical polymerization to heterogeneous systems such as emulsion and miniemulsion polymerization may provide process and economic advantages over the traditional homoge- neous bulk and solution polymerizations. However, adaptation of living radical chemistry to aqueous dispersions poses several challenges relating to maintaining effective control over the growth of living chains. These chal- lenges originate from having two or even three phases in the reaction mixture, which can lead to issues related to phase partitioning of the controlling agent, transport of the controlling agent between phases, the role of aqueous phase kinetics, and the phenomena of particle nucleation and colloidal stability. This review examines recent progress in this area, with an emphasis on unresolved issues and future opportunities. q 2002 Elsevier Science Ltd. All rights reserved. Keywords: Living radical polymerization; Controlled radical polymerization; Stable free radical polymerization; Atom transfer radical polymerization; Reversible addition±fragmentation transfer; Degenerative transfer; Emulsion polymerization; Mini- emulsion polymerization Contents 1. Introduction ..................................................................1040 1.1. Scope of the review ........................................................1040 1.2.
    [Show full text]
  • Dormant Polymers and Their Role in Living and Controlled Polymerizations; Influence on Polymer Chemistry, Particularly on the Ring Opening Polymerization
    polymers Review Dormant Polymers and Their Role in Living and Controlled Polymerizations; Influence on Polymer Chemistry, Particularly on the Ring Opening Polymerization Stanislaw Penczek *, Julia Pretula and Piotr Lewi ´nski Centre of Molecular and Macromolecular Studies of Polish Academy of Sciences, Sienkiewicza 112, 90-363 Lodz, Poland; [email protected] (J.P.); [email protected] (P.L.) * Correspondence: [email protected]; Tel.: +48-42-681-9815 Received: 2 November 2017; Accepted: 23 November 2017; Published: 25 November 2017 Abstract: Living polymerization discovered by Professor Szwarc is well known to all chemists. Some of the living polymerizations involve dormancy, a process in which there is an equilibrium (or at least exchange) between two types of living polymers, namely active at the given moment and dormant at this moment and becoming active in the process of activation. These processes are at least equally important although less known. This mini review is devoted to these particular living polymerizations, mostly polymerizations by the Ring-Opening Polymerization mechanisms (ROP) compared with some selected close to living vinyl polymerizations (the most spectacular is Atom Transfer Radical Polymerization (ATRP)) involving dormancy. Cationic polymerization of tetrahydrofuran was the first one, based on equilibrium between oxonium ions (active) and covalent (esters) dormant species, i.e., temporarily inactive, and is described in detail. The other systems discussed are polymerization of oxazolines and cyclic esters as well as controlled radical and cationic polymerizations of vinyl monomers. Keywords: dormant polymers; living polymerization; controlled polymerization; ring-opening polymerization 1. Introduction Professor Michael (Michał in Polish) Szwarc’s contributions to the chemical science are not only related to polymers and to his discovery of living and (less known) dormant polymers [1].
    [Show full text]
  • Living Polymerization of Olefins with Ansa-Dimethylsilylene
    Polymer Journal (2011) 43, 331–351 & The Society of Polymer Science, Japan (SPSJ) All rights reserved 0032-3896/11 $32.00 www.nature.com/pj INVITED REVIEW Living polymerization of olefins with ansa-dimethyl- silylene(fluorenyl)(amido)dimethyltitanium-based catalysts Takeshi Shiono This article reviews the living homopolymerization and copolymerization of propene, 1-alkene and norbornene with ansa- 3 1 t dimethysilylene(fluorenyl)(amido)dimethyltitanium, Me2Si(g -C13H8)(g -N Bu)TiMe2 and its derivatives, correlating the effects of cocatalysts, solvents, polymerization conditions and the substituents of the fluorenyl ligand with catalytic features, such as livingness, initiation efficiency, propagation rate, syndiospecificity and copolymerization ability. The synthesis of novel olefin block copolymers and their catalytic synthesis are also introduced using this living system. Polymer Journal (2011) 43, 331–351; doi:10.1038/pj.2011.13 Keywords: cycloolefin copolymer; living polymerization; norbornene; propene; single-site catalyst; syndiospecific polymerization; 1-alkene A living polymerization system, in which neither chain transfer nor zation of propene and a 1-alkene but also a living homopolymeriza- deactivation occurs, affords polymers with predictable molecular tion and copolymerization of norbornene with a 1-alkene. We weights and narrow molecular weight distributions (MWDs). Living investigated the effect of cocatalyst, solvent and the ligand of the polymerization techniques are utilized for the synthesis of terminally titanium complex on propene polymerization in terms of the living- functionalized polymers and block copolymers. Another feature of ness of the system. We also synthesized novel olefin block copolymers living polymerization is its simple kinetics. Because neither chain with the living system. This article reviews the characteristics of transfer nor deactivation occurs in living polymerization, the number 1-based catalysts for tailor-made polyolefins.
    [Show full text]
  • Photo-Mediated Ring-Opening Metathesis Polymerization
    Photo-Mediated Ring-Opening Metathesis Polymerization Oleg Davydovich Literature Seminar November 8, 2018 Ring-opening metathesis polymerization (ROMP) is a widely-used technqiue to produce bulk amounts of polymer. In 1976, the first commercial use of ROMP was used to synthesize poly(norbornene) which was sold under the trade Norsorex (used in shoe-parts, bumpers and anti- vibration materials).1 Since then, the industrial utility of ROMP has significantly increased, producing new polymers based on monomers such as dicyclopentadiene, cycloocetene and tetracyclododecene. ROMP is used to polymerize cyclic olefins via transition-metal alkylidene catalysts. The mechanism of ROMP begins with a [2+2] cycloaddition reaction between the cyclic olefin and alkylidene catalyst generating a cyclobutane intermediate. The intermediate then undergoes cycloreversion, rearranging π-bonds in the opposite fashion, producing a new alkylidene and olefin species. The reaction is driven forward by the relief of ring strain in the cyclic olefin, propagating until complete monomer consumption. Termination occurs via quenching with a vinyl ether, removing the alkylidene from the polymer backbone.2 Scheme 1: Ring-Opening Metathesis Polymerization Mechanism ROMP is a “living polymerization” which refers to a lack of chain transfer or termination events. “Living polymerization” reactions are characterized as having low molecular weight distributions (polydispersity index < 1.5), fast initiation rates compared to propagation rates, and a linear relationship between the number average molecular weight and monomer conversion.3 Thus, ROMP offers a route to synthesizing polymers with narrow molecular weight distributions and predictable molecular weights. These characteristics provide methods to generate more exquisite systems such as block-copolymers and end-functionalized polymers.
    [Show full text]