Organocatalytic Polymerization - Springer · Just after the proposal of organocatalysis, Hedrick...

Organocatalytic Polymerization

Toshifumi Satoh*Faculty of Engineering, Division of Biotechnology and Macromolecular Chemistry, Laboratory of Molecular MaterialsChemistry, Sapporo, Japan

Synonyms

Group transfer polymerization; Metal-free polymerization; Organocatalytic polymerization reaction

Definition

Organocatalytic polymerization, i.e., polymerization using an organocatalyst, is a metal-free greenstrategy for polymer synthesis. For polymer chemistry, the reported organocatalytic polymerizationsare usually the living polymerization systems under mild conditions compared to the conventionalpolymerizations using metal-based catalysts.

Introduction

An organocatalyst, which was proposed by MacMillan et al.[1] in 2000, is defined as an organiccompound consisting of nonmetallic elements, such as carbon, hydrogen, oxygen, nitrogen, phos-phorus, and sulfur, and having a catalytic activity, with the following advantages: (1) highertolerance toward moisture and oxygen, (2) more tunable catalytic activity by changing the chemicalstructure, (3) lower toxicity, and (4) easier immobilization onto carriers, such as polymer substrates,as compared to those of traditional metal-based catalysts. Thus, organocatalysts have been recog-nized as third-generation catalysts following enzymes and metal-based catalysts.

Just after the proposal of organocatalysis, Hedrick and co-workers reported the controlled ring-opening polymerization (ROP) of L-lactide catalyzed by 4-dimethylaminopyridine (DMAP) as theorganocatalyst, which is the breakthrough study in the field of polymer chemistry [2]. Theorganocatalytic approaches have been applied to many polymerization techniques, such as theROP, group transfer polymerization (GTP), and condensation polymerization, to synthesizea well-defined polymer. In this entry, the ROP and GTP using an organocatalyst were summarized.

Monomers and Catalysts for Organocatalytic Ring-OpeningPolymerization

Various ROPs have been reported using organocatalysts with simple structures, which have theadvantage of being commercially available or readily synthesized in a few steps. As examples,lactide (LA), b-butyrolactone (BL), d-valerolactone (VL), e-caprolactone (CL), morpholine-2,6-dione (MDO), 1,5-dioxepan-2-one (DXO), e-caprolactam (CLa), trimethylene carbonate (TMC),

*Email: [email protected]

Encyclopedia of Polymeric NanomaterialsDOI 10.1007/978-3-642-36199-9_194-1# Springer-Verlag Berlin Heidelberg 2014

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2,2,5,5-tetramethyl-1-oxa-2,5-disilacyclopentane (TMOSC), hexamethylcyclotrisiloxane (D3),dipropyl cyclopropane-1,1-dicarboxylate (CPDC), 2-isopropoxy-2-oxo-1,3,2-dioxaphospholane(IPP), N-methoxyethyl phospholane amidate (MOEPA), and epoxides, such as ethylene oxide(EO), propylene oxide (PO), 1,2-butylene oxide (BO), and styrene oxide (SO), are polymerizedusing organocatalysts, such as the pyridine catalyst, guanidine/amidine catalyst, phosphine catalyst,N-heterocyclic carbene (NHC) catalyst, phosphazene-based catalyst, thiourea/amine catalyst,bifunctional catalyst, and organic acid catalysts such as sulfonic acid, phosphoric acid, carboxylicacid, and amino acid (Figs. 1 and 2) [3–13]. The combination of the monomer and the catalyst is veryimportant to produce a polymer having a high molecular weight and narrow polydispersity (PDI).For example, the polymerizations of LA and lactone using NHC take place in a living manner,whereas NHC hardly controls the polymerization of MDO.

Organocatalytic Ring-Opening Polymerization Using Base/NucleophilicAgent

For the organocatalytic ROP, organic bases are the main focus due to their highly catalytic ability. Inthe presence of an alcohol initiator, the polymerization proceeds via nucleophilic monomer activa-tion or via basic activation of the initiator/propagating chain-end, as shown in Fig. 3.

In 2001, Hedrick et al. reported the first organocatalytic approach to the living ROP of LA usingLewis basic amines, such as DMAP and 4-pyrrolidinopyridine (PPY), as transesterification catalysts

Fig. 1 Cyclic monomers employed for organocatalytic ring-opening polymerization


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Fig. 2 Organocatalysts employed for ROP

a

b

Fig. 3 (a) Monomer activation mechanism and (b) initiator/chain-end activation mechanism for ROP of LA by organicbase/nucleophilic agent


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[2]. Using DMAP as a catalyst and ethanol as an initiator, polylactides (PLAs) up to degree ofpolymerization (DP) of ca. 100 with narrow PDIs (<1.13) are prepared, while no polymerizationwas detectable in the absence of the initiator. The correlation between the molecular weight andmonomer conversion is consistent with a living nature. The above catalysts show comparableactivities, producing a well-defined PLAwith a molecular weight that closely tracks the monomer-to-initiator ratio with extremely narrow PDIs.

Phosphines, such as n-Bu3P, Ph2MeP, and Ph3P, also produce a well-defined PLA in the presenceof an alcohol initiator due to strong activation of the monomer, and the polymerization activity iscontrolled by the substituents on the phosphine; the alkyl-substituted phosphines are more activethan the aryl-substituted ones [14].

For nucleophilic monomer activation, NHCs, such as IMes, Triaz, and IPr, are the mostestablished catalysts [15, 16]. The NHC activates the carbonyl group of the monomer and formszwitterionic chain-ends leading to a well-defined cyclic PLA in the absence of an alcohol initiatorand to a linear PLA in the presence of an initiator, as shown in Fig. 4. NHCs show a catalytic abilityalso for the ROP of lactones, cyclic carbonates, cyclic siloxanes, and epoxides, meaning that thenucleophilic monomer activation is a reliable method [17–19].

The guanidine and amidine bases, such as 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), N-methyl-TBD (MTBD), and 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU), are effective organocatalysts forthe ROP of LA in nonpolar solvents [20]. The polymerization of LA using MTBD and DBUproduced PLAs having a DP of up to ca. 500 with a narrow PDI (<1.1), whereas neither of thecatalysts is active for the polymerization of BL, VL, and CL even at up to a 20 mol% catalyst loadingin the solvent. TBD is shown to polymerize LA, BL, VL, CL, TMC, IPP, and MOEPA in a fast andcontrolled manner, but its higher transesterification activity results in broadening of the PDI upon thefull conversion [7, 8, 20, 21]. TBD is capable of bifunctional activation of both the monomer and thealcohol, whereas DBU and MTBD only activate the alcohol.

The combination of monomer activation and chain-end activation has constructed a new para-digm for the ROP. The thiourea/amine (TU/A)-type catalyst is the first such catalyst to introduce thisconcept [22, 23]. The TU/A-type catalysts have two activation sites in one molecule, as shown inFig. 5. Thiourea (TU) works as an H-bond donor to electrophilically activate the carbonyl group ofmonomer, and the amine as an H-bond acceptor to enhance the nucleophilicity of propagating chain-end. The H-bond donor and acceptor also work as separated molecules; thus, the wide-range

Fig. 4 Synthesis of linear and cyclic PLAs by zwitterionic polymerization


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combination of the two molecules has been screened. For example, a variety of tertiary amines wereevaluated as cocatalysts for TU, and the result showed that (�)-sparteine and tris[2-(dimethylamino)ethyl]amine (Me6TREN) have the ideal ability by a chelate effect [23, 24]. The combination of DBUand TU also showed the ability for the polymerizations of VL and CL, which were not achieved byonly using an H-bond acceptor or donor [20].

Schwesinger and co-workers synthesized phosphazene bases, a kind of organic superbase, in1985 [25, 26], which is classified as an uncharged nitrogen base without metal elements and has theperalkylated triaminoiminophosphorane structural type. The basicity (pKBH) of the phosphazenebases increases with the increasing number of triaminophosphorus groups (�N ¼ P-(NR2)3) in themolecule [27].

The phosphazene bases, 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP), tert-butylimino-tris(dimethylamino)phosphorane (t-Bu-P1),1-tert-butyl-2,2,4,4,4-pentakis(dimethylamino)-2L5,4L5-catenadi(phosphazene) (t-Bu-P2), and1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranylidenamino]-2L5,4L5-catenadi(phosphazene) (t-Bu-P4), were also used as the catalyst for the polymerization ofvarious monomers in the field of polymer chemistry. For example, t-Bu-P2 shows a catalytic activityfor the ROP of LA [28, 29], a lactone [28], a six-membered cyclic carbonate [30], and cyclosiloxane[31] in the presence of an alcohol initiator. Furthermore, t-Bu-P4 has a high catalytic activity for thepolymerization of an epoxide [11–13], lactam [9], cyclopropane [6], and five-membered cycliccarbonate (Fig. 6) [32].

Organocatalytic Ring-Opening Polymerization Using Cationic Agent

Cationic organocatalysts have been also used for the ROP of a variety of cyclic heterocycles, such asVL, CL, LA, glycolide, and DXO. In 1986, Kricheldorf et al. reported that trifluoromethanesulfonicacid (TfOH) andmethyl triflate (TfOMe) were useful initiators for the ROP of LA [33, 34]. However,the ROP is not living under the reported optimized conditions.

In 2000, Endo et al. reported the controlled ROP of VL and CL using the HCl·Et2O catalyst/alcohol initiator system at room temperature [35]. For example, polylactones (molecular weights up

Fig. 5 Proposed activation pathway for ROP of LA using TU/A catalyst

Fig. 6 Polymerization of epoxide using t-Bu-P4 and alcohol initiators


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to 14,000 g · mol�1) were obtained with narrow PDIs in the range of 1.08–1.27. The ROP isproposed to proceed through an activated monomer mechanism in which the acid activates themonomer and facilitates ring opening by the initiating or propagating alcohol (ROH), as shown inFig. 7a. Using this catalytic system, Jorome et al. prepared a high molecular weight (up to 40,000 g ·mol�1) PVL with narrow PDIs (>1.05) at 0 �C [36]. They also prepared a series of a-functionalizedPVLs using functional alcohols such as 5-norbornene-2-methanol, 3-bromo-ethanol, 2-hydroxyethel acrylate, etc. (Fig. 7b).

An organic acid and amino acid with an alcohol initiator also catalyzed the controlled ROP oflactones, and the catalyst efficiency was on the order of tartaric acid > citric acid > lactic acid >proline [37]. The star PCL has been synthesized using fumaric acid in the present of pentaerythritolas the initiator [38].

Sulfonic acid can be used for the ROP of LA and BL; trifluoromethane sulfonic acid (TfOH)sufficiently promotes the polymerization of LA by enhancing the monomer activation due to itsextremely strong acidity (pKa�13 in CH2Cl2), and methanesulfonic acid (MsOH) contributes to thecontrolled polymerization of BL due to its strong acidity (pKa �2 in CH2Cl2) [39, 40]. TfOH andMsOH are also active for the controlled ROP of CL [41].

For expanding the scope and limitation of the organic acid-catalyzed ROP, Kakuchi and Satohet al. reported the controlled ROP of CL and VL using HNTf2 and C6F5CHTf2 as organocatalystsand an alcohol as an initiator [10, 42, 43]. The polymerizations homogeneously proceed to affordPCL and PVL with controlled molecular weights and narrow PDIs. The 0.1 mol% catalyst based onthe initial monomer feed is sufficient to catalyze the ROP at ambient temperature. HNTf2 is alsoeffective to prepare PDXO and PLAwith a narrow PDI.

Diphenylphosphate (DPP) are also able to efficiently mediate the ROP of VL, CL, and cycliccarbonates at a high monomer conversion (>95 %) at room temperature, achieving the high controllevels of the polymer structure with a high molecular weight (up to 27,500) and narrow PDI(ca. 1.07–1.13) (Fig. 8) [44]. In addition, the block copolymerizations of PVL, PCL, and TMCsuccessfully proceed to afford PVL-b-PCL, TMC-b-PVL, and TMC-b-PCL, regardless of themonomer addition sequence [45].

a

b

Fig. 7 (a) Activated monomer mechanism by HCl Et2O and (b) synthesis of end-functionalized PVL


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Organocatalytic Group Transfer Polymerization

Although most of the efforts regarding the organocatalytic polymerization have been devoted onlyto the ROP, Taton andGnanou et al. andWaymouth et al. reported in 2007–2008 that NHC is capableof efficiently catalyzing the group transfer polymerization (GTP) of both MMA and tert-butylacrylate in a controlled/living fashion [46, 47]. The application of organocatalysts in GTP hasdemonstrated an organocatalytic vinyl polymerization. Besides, organocatalysts have been found to

Fig. 8 DPP-catalyzed ROP of cyclic esters and cyclic carbonates

Fig. 9 Organocatalysts employed for GTP


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work as versatile catalysts for GTP beyond the limitations of the conventional GTP in terms ofcatalytic activity, polymerizable monomers, molecular weight control, and polymer structures thatcan be synthesized. The following organocatalysts have already been employed in GTP: NHCs,phosphazene bases, proazaphosphatrane, phosphine, tris(pentafluorophenyl)borane (B(C6F5)3) witha silylating agent, triphenylcarbenium salts, and strong organic Brønsted acids (Fig. 9) [48, 49].

Since 2007, NHCs [50–52], proazaphosphatranes [53–55], phosphazene bases [25, 26, 56, 57],and phosphines [58] have been employed for the GTP as Lewis base organocatalysts. In particular,NHCs are revealed to be capable of efficiently catalyzing the organocatalytic GTP of alkyl acrylates,N,N-dimethylacrylamide, and methacrylonitrile in addition to alkyl methacrylates, though conven-tional Lewis base catalysts are only suitable for the polymerization of methacrylates. The Lewis baseorganocatalysts are regularly used at ca. 0.5–20 mol% for the initiator to obtain polymers with a PDIless than 1.20.

Fig. 10 Proposed associative and dissociative mechanisms of Lewis base-catalyzed GTP


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For the GTP using Lewis base catalysts, two different mechanisms have been proposed as theassociative mechanism and the dissociative mechanism, as shown in Fig. 10. In the associativemechanism, a Lewis base (B) coordinates to the silyl group of the initiator (silylketene acetal: SKA)or of the propagating end to activate it. The coordinated complex then reacts with an incomingmonomer in a concerted fashion. At the same time, the silyl group of the original propagating endtransfers to the incoming monomer to form the new propagating end. On the other hand, based on thedissociative mechanism, B interacts with the silyl enolate and reversibly generates an enolate anion,which adds to a monomer with the normal Michael reaction mechanism. The enolate anion canreversibly form a hypervalent complex with another silyl enolate end to form dormant species. GTPsusing Lewis base organocatalysts generally undergo fast initiation and propagation rates, but poorcontrol over the stereoregularity of the polymers in comparison to the GTP using Lewis acidcatalysts.

The Lewis acid-catalyzed GTP is considered to proceed with the activation of a monomer bya Lewis acid (A), as illustrated in Fig. 11. Conventional Lewis acid catalysts, such as zinc halides andalkyl aluminums, are only suitable for the polymerization of acrylates due to their low catalyticactivity, i.e., weak Lewis acidity, and 10–20 mol% of the Lewis acids based on the amount of themonomer is required for the controlled polymerization [59]. However, the emergence of highlyacidic Lewis organocatalysts has broken the limitation of conventional Lewis acid-catalyzed GTPs.The GTPs of alkyl methacrylates, N,N-dimethylacrylamide, a-methylenebutyrolactone, andg-methyl-a-methylenebutyrolactone have been newly achieved with the Lewis acid organocatalysts,such as tris(pentafluorophenyl)borane (B(C6F5)3) with a silylating agent, triphenylcarbenium salts,and strong organic Brønsted acids [60–68]. The Lewis acid organocatalysts are regularly used atca. 1–50 mol% for the initiator to obtain polymers with Mw/Mn values less than 1.15.

Summary

As described above, the organocatalytic polymerization has provided novel synthetic strategies forthe macromolecular design with a specific structure and function. Additionally, the use oforganocatalysts for polymer synthesis can provide advantages in microelectronic or biomedicalapplications in which the presence of metal residues in the final material can be deleterious to theirend use. In conclusion, the organocatalytic polymerization still has much potential to bring aboutfurther development in polymer chemistry. The author firmly believes that the aforementioned

Fig. 11 Plausible mechanism of the Lewis acid-catalyzed GTP


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introduction would lead the readers to a comprehensive understanding of organocatalyticpolymerization.

Related Entries

▶Anionic Ring-Opening Polymerization▶Cationic Ring-Opening Polymerization▶Living Anionic Addition Polymerization▶Living Polymerization (Overview)

References

1. Ahrendt KA, Borths CJ, MacMillan DWC (2000) New Strategies for Organic Catalysis: TheFirst Highly Enantioselective Organocatalytic Diels-Alder Reaction. J Am Chem Soc122(17):4243–4244

2. Nederberg F, Connor EF, Möller M, Glauser T, Hedrick JL (2001) New Paradigms for OrganicCatalysts: The First Organocatalytic Living Polymerization. Angew Chem Int Ed40(14):2712–2715

3. Kamber NE, Jeong W, Waymouth RM, Pratt RC, Lohmeijer BGG, Hedrick JL (2007)Organocatalytic Ring-Opening Polymerization. Chem Rev 107(12):5813–5840

4. Kiesewetter MK, Shin EJ, Hedrick JL, Waymouth RM (2010) Organocatalysis: Opportunitiesand Challenges for Polymer Synthesis. Macromolecules 43(5):2093–2107

5. Dove AP (2012) Organic Catalysis for Ring-Opening Polymerization. ACS Macro Lett1(12):1409–1412

6. Illy N, Boileau S, Penelle J, Barbier V (2009) Metal-Free Activation in the Anionic Ring-Opening Polymerization of Cyclopropane Derivatives. Macromol Rapid Commun30(20):1731–1735

7. Iwasaki Y, Yamaguchi E (2010) Synthesis of Well-Defined ThermoresponsivePolyphosphoester Macroinitiators Using Organocatalysts. Macromolecules 43(6):2664–2666

8. Zhang S,Wang H, Shen Y, Zhang F, Seetho K, Zou J, Taylor J-SA, Dove AP,Wooley KL (2013)A Simple and Efficient Synthesis of an Acid-Labile Polyphosphoramidate by Organobase-Catalyzed Ring-Opening Polymerization and Transformation to Polyphosphoester Ionomers byAcid Treatment. Macromolecules 46(13):5141–5149

9. Memenger W Jr, Campbell GC, Davidson F (1996) Poly(aminophosphazene)s and Protopho-sphatranes Mimic Classical Strong Anionic Base Catalysts in the Anionic Ring-OpeningPolymerization of Lactams. Macromolecules 29(20):6475–6480

10. Makiguchi K, Kikuchi S, Satoh T, Kakuchi T (2013) Synthesis of block and end-functionalizedpolyesters by triflimide-catalyzed ring-opening polymerization of e-caprolactone, 1,5-dioxepan-2-one, and rac-lactide. J Polym Sci Part A Polym Chem 51(11):2455–2463

11. Esswein B, Möller M (1996) Polymerization of Ethylene Oxide with Alkyllithium Compoundsand the Phosphazene Base “tBu-P4”. Angew Chem Int Ed 35(6):623–625

12. Misaka H, Tamura E, Makiguchi K, Kamoshida K, Sakai R, Satoh T, Kakuchi T (2012)Synthesis of end-functionalized polyethers by phosphazene base-catalyzed ring-opening poly-merization of 1,2-butylene oxide and glycidyl ether. J Polym Sci Part A Polym Chem50(10):1941–1952


of 14





13. Misaka H, Sakai R, Satoh T, Kakuchi T (2011) Synthesis of High Molecular Weight and End-Functionalized Poly(styrene oxide) by Living Ring-Opening Polymerization of Styrene OxideUsing the Alcohol/Phosphazene Base Initiating System. Macromolecules 44(23):9099–9107

14. Myers M, Connor EF, Glauser T, Mock A, Nyce G, Hedrick JL (2002) Phosphines: Nucleo-philic organic catalysts for the controlled ring-opening polymerization of lactides. J Polym SciPart A Polym Chem 40(7):844–851

15. Connor EF, Nyce GW, Myers M, Mock A, Hedrick JL (2002) First Example of N-HeterocyclicCarbenes as Catalysts for Living Polymerization: Organocatalytic Ring-Opening Polymeriza-tion of Cyclic Esters. J Am Chem Soc 124(6):914–915

16. Kamber NE, JeongW, Gonzalez S, Hedrick JL,Waymouth RM (2009) N-Heterocyclic Carbenesfor the Organocatalytic Ring-Opening Polymerization of e-Caprolactone. Macromolecules42(5):1634–1639

17. Nederberg F, Trang V, Pratt RC, Mason AF, Frank CW, Waymouth RM, Hedrick JL (2007)New Ground for Organic Catalysis: A Ring-Opening Polymerization Approach toHydrogels. Biomacromolecules 8(11):3294–3297

18. Lohmeijer BG, Dubois G, Leibfarth F, Pratt RC, Nederberg F, Nelson A, Waymouth RM,Wade C, Hedrick JL (2006) Organocatalytic Living Ring-Opening Polymerization of CyclicCarbosiloxanes. Org Lett 8(21):4683–4686

19. Raynaud J, Absalon C, Gnanou Y, Taton D (2009) N-Heterocyclic Carbene-Induced Zwitter-ionic Ring-Opening Polymerization of Ethylene Oxide and Direct Synthesis of a,o-Difunctionalized Poly(ethylene oxide)s and Poly(ethylene oxide)-b-poly(ε-caprolactone)Block Copolymers. J Am Chem Soc 131(9):3201–3209

20. Lohmeijer BGG, Pratt RC, Leibfarth F, Logan JW, Long DA, Dove AP, Nederberg F, Choi J,Wade C, Waymouth RM, Hedrick JL (2006) Guanidine and Amidine Organocatalysts for Ring-Opening Polymerization of Cyclic Esters. Macromolecules 39(25):8574–8583

21. Jaffredo CG, Carpentier J-F, Guillaume SM (2012) Controlled ROP of b-Butyrolactone SimplyMediated by Amidine, Guanidine, and Phosphazene Organocatalysts. Macromol RapidCommun 33(22):1938–1944

22. Dove AP, Pratt RC, Lohmeijer BGG, Waymouth RM, Hedrick JL (2005) Thiourea-BasedBifunctional Organocatalysis: Supramolecular Recognition for Living Polymerization. J AmChem Soc 127(40):13798–13799

23. Pratt RC, Lohmeijer BGG, Long DA, Lundberg PNP, Dove AP, Li HB, Wade CG, WaymouthRM, Hedrick JL (2006) Exploration, Optimization, and Application of SupramolecularThiourea–Amine Catalysts for the Synthesis of Lactide (Co)polymers. Macromolecules39(23):7863–7871

24. Coady DJ, Engler AC, Horn HW, Bajjuri KM, Fukushima K, Jones GO, Nelson A, Rice JE,Hedrick JL (2012) Catalyst Chelation Effects in Organocatalyzed Ring-Opening Polymeriza-tion of Lactide. Macro Lett 1(1):19–22

25. Schwesinger R (1985) Extremely strong, non-ionic bases: syntheses and applications. Chimia39:269–272

26. Schwesinger R, Schlemper H (1987) Peralkylated Polyaminophosphazenes— ExtremelyStrong, Neutral Nitrogen Bases. Angew Chem Int Ed 26(11):1167–1169

27. Schwesinger R, Schlemper H, Hasenfratz C, Willaredt J, Dambacher T, Breuer T, Ottaway C,Fletschinger M, Boele J, Fritz H, Putzas D, Rotter HW, Bordwell FG, Satish AV, Ji GZ, PetersEM, Peters K, vonSchnering HG, Walz L (1996) Extremely Strong, Uncharged AuxiliaryBases; Monomeric and Polymer-Supported Polyaminophosphazenes (P2–P5). Liebigs Ann1996(7):1055–1081


of 14

28. Zhang L, Nederberg F, Pratt RC, Waymouth RM, Hedrick JL, Wade CG (2007) PhosphazeneBases: A New Category of Organocatalysts for the Living Ring-Opening Polymerization ofCyclic Esters. Macromolecules 40(12):4154–4158

29. Zhang L, Nederberg F, Messman JM, Pratt RC, Hedrick JL, Wade CG (2007) OrganocatalyticStereoselective Ring-Opening Polymerization of Lactide with Dimeric Phosphazene Bases.J Am Chem Soc 129(42):12610–12611

30. Helou M, Miserque O, Brusson J, Carpentier J, Guillaume SM (2010) Organocatalysts for theControlled “Immortal” Ring-Opening Polymerization of Six-Membered-Ring Cyclic Carbon-ates: A Metal-Free, Green Process. Chem Eur J 16(46):13805–13813

31. Molenberg A, Möller M (1997) Polymerization of cyclotrisiloxanes by organolithium com-pounds and P2-Et base. Macromol Chem Phys 198(3):717–726

32. Yang H, Yan M, Pispas S, Zhang G (2011) Synthesis of Poly[(ethylene carbonate)-co-(ethyleneoxide)] Copolymer by Phosphazene-Catalyzed ROP. Macromol Chem Phys212(23):2589–2593

33. Kricheldorf HR, Dunsing R (1986) Polylactones, 8. Mechanism of the cationic polymerizationof L,L-dilactide. Macromol Chem 187(7):1611–1625

34. Kricheldorf HR, Kreiser I (1987) Polylactones, 11. Cationic copolymerization of glycolide withL,L-dilactide. Macromol Chem 188(8):1861–1873

35. Shibasaki Y, Sanada H, Yokoi M, Sanda F, Endo T (2000) Activated Monomer CationicPolymerization of Lactones and the Application to Well-Defined Block Copolymer Synthesiswith Seven-Membered Cyclic Carbonate. Macromolecules 33(12):4316–4320

36. Lou XD, Detrembleur C, Jerome R (2002) Living Cationic Polymerization of d-Valerolactoneand Synthesis of High Molecular Weight Homopolymer and Asymmetric Telechelic and BlockCopolymer. Macromolecules 35(4):1190–1195

37. Casas J, Persson PV, Iversen T, Cordova A (2004) Direct Organocatalytic Ring-OpeningPolymerizations of Lactones. Adv Synth Catal 346(9–10):1087–1089

38. Sanda F, Sanada H, Shibasaki Y, Endo T (2002) Star Polymer Synthesis from e-CaprolactoneUtilizing Polyol/Protonic Acid Initiator. Macromolecules 35(3):680–683

39. Bourissou D, Martin-Vaca B, Dumitrescu A, Graullier M, Lacombe F (2005) ControlledCationic Polymerization of Lactide. Macromolecules 38(24):9993–9998

40. Couffin A, Martin-Vaca B, Bourissou D, Navarro C (2014) Selective O-acyl ring-opening of b-butyrolactone catalyzed by trifluoromethane sulfonic acid: application to the preparation ofwell-defined block copolymers. Polym Chem 5(1):161–168

41. Basko M, Kubisa P (2006) Cationic copolymerization of e-caprolactone and L,L-lactide by anactivated monomer mechanism. J Polym Sci Part A Polym Chem 44(24):7071–7081

42. Kakuchi R, Tsuji Y, Chiba K, Fuchise K, Sakai R, Satoh T, Kakuchi T (2010) Controlled/LivingRing-Opening Polymerization of d-Valerolactone Using Triflylimide as an Efficient CationicOrganocatalyst. Macromolecules 43(17):7090–7094

43. Makiguchi K, Satoh T, Kakuchi T (2011) Synthesis of various end-functionalized polyesters bycontrolled/living ring-opening polymerization of lactones using pentafluorophenylbis(triflyl)methane. J Polym Sci Part A Polym Chem 49(17):3769–3777

44. Makiguchi K, Satoh T, Kakuchi T (2011) Diphenyl Phosphate as an Efficient CationicOrganocatalyst for Controlled/Living Ring-Opening Polymerization of d-Valerolactone ande-Caprolactone. Macromolecules 44(7):1999–2005

45. Makiguchi K, Ogasawara Y, Kikuchi S, Satoh T, Kakuchi T (2013) Diphenyl Phosphate as anEfficient Acidic Organocatalyst for Controlled/Living Ring-Opening Polymerization of


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Trimethylene Carbonates Leading to Block, End-Functionalized, and MacrocyclicPolycarbonates. Macromolecules 46(5):1772–1782

46. Raynaud J, Ciolino A, Baceiredo A, DestaracM, Bonnette F, Kato T, Gnanou Y, Taton D (2008)Harnessing the Potential of N-Heterocyclic Carbenes for the Rejuvenation of Group-TransferPolymerization of (Meth)Acrylics. Angew Chem Int Ed 47(29):5390–5393

47. Scholten MD, Hedrick JL, Waymouth RM (2008) Group Transfer Polymerization of AcrylatesCatalyzed by N-Heterocyclic Carbenes. Macromolecules 41(20):7399–7404

48. Chen EY-X (2009) Coordination Polymerization of Polar Vinyl Monomers by Single-SiteMetal Catalysts. Chem Rev 109(11):5157–5214

49. Fuchise K, Chen Y, Satoh T, Kakuchi T (2013) Recent progress in organocatalytic grouptransfer polymerization. Polym Chem 4(16):4278–4291

50. Fèvre M, Pinaud J, Gnanou Y, Vignolle J, Taton D (2013) N-Heterocyclic carbenes (NHCs) asorganocatalysts and structural components in metal-free polymer synthesis. Chem Soc Rev42(5):2142–2172

51. Marion N, Diez-Gonzalez S, Nolan SP (2007) N-heterocyclic carbenes asorganocatalysts. Angew Chem Int Ed 46(17):2988–3000

52. Enders D, Niemeier O, Henseler A (2007) Organocatalysis by N-Heterocyclic Carbenes. ChemRev 107(12):5606–5655

53. Verkade JG, Kisanga PB (2003) Proazaphosphatranes: a synthesis methodology trip from theirdiscovery to vitamin A. Tetrahedron 59(40):7819–7858

54. Chintareddy VR, Wadhwa K, Verkade JG (2009) P(PhCH2NCH2CH2)3N Catalysis ofMukaiyama Aldol Reactions of Aliphatic, Aromatic, and Heterocyclic Aldehydes andTrifluoromethyl Phenyl Ketone. J Org Chem 74(21):8118–8132

55. Kakuchi T, Chen Y, Kitakado J, Mori K, Fuchise K, Satoh T (2011) Organic Superbase as anEfficient Catalyst for Group Transfer Polymerization of Methyl Methacrylate. Macromolecules44(12):4641–4647

56. Schwesinger R, Hasenfratz C, Schlemper H, Walz L, Peters E-M, Peters K, von Schnering HG(1993) How Strong and How Hindered Can Uncharged Phosphazene Bases Be?. Angew ChemInt Ed 32(9):1361–1363

57. Chen Y, Fuchise K, Narumi A, Kawaguchi S, Satoh T, Kakuchi T (2011) Core-First Synthesis ofThree-, Four-, and Six-Armed Star-Shaped Poly(methyl methacrylate)s by Group TransferPolymerization Using Phosphazene Base. Macromolecules 44(23):9091–9098

58. Matsukawa S, Okano N, Imamoto T (2000) Phosphine catalyzed aldol reaction between ketenesilyl acetals and aldehydes: nucleophilic O–Si and C–Si bond cleavage by phosphines. Tetra-hedron Lett 41(1):103–107

59. Hertler WR, Sogah DY, Webster OW (1984) Group-transfer polymerization. 3. Lewis acidcatalysis. Macromolecules 17(7):1415–1417

60. Ute K, Ohnuma H, Kitayama T (2000) Combination of Tris(pentafluorophenyl)borane andTrialkylsilyl Triflate as an Efficient Catalyst System for the Group Transfer Polymerization ofAcrylates. Polym J 32(12):1060–1062

61. Zhang Y, Chen EY-X (2008) Controlled Polymerization of Methacrylates to High MolecularWeight Polymers Using Oxidatively Activated Group Transfer Polymerization Initiators. Mac-romolecules 41(1):36–41

62. Zhang Y, Chen EY-X (2008) Structure−Reactivity Relationships in Bimolecular-ActivatedMonomer Polymerization of (Meth)acrylates Using Oxidatively Activated Group 14 KeteneAcetals. Macromolecules 41(17):6353–6360


of 14

63. Miyake GM, Zhang Y, Chen EY-X (2010) Living Polymerization of Naturally RenewableButyrolactone-Based Vinylidene Monomers by Ambiphilic Silicon Propagators. Macromolecules43(11):4902–4908

64. Zhang Y, Gustafson LO, Chen EY-X (2011) Dinuclear Silylium-enolate Bifunctional ActiveSpecies: Remarkable Activity and Stereoselectivity toward Polymerization of Methacrylate andRenewable Methylene Butyrolactone Monomers. J Am Chem Soc 133(34):13674–13684

65. Kakuchi R, Chiba K, Fuchise K, Sakai R, Satoh T, Kakuchi T (2009) Strong Brønsted Acid as aHighly Efficient Promoter for Group Transfer Polymerization of Methyl Methacrylate. Macro-molecules 42(22):8747–8750

66. Chen Y, Takada K, Fuchise K, Satoh T, Kakuchi T (2012) Synthesis of syndiotactic-rich star-shaped poly(methyl methacrylate) by core-first group transfer polymerization using N-(trimethylsilyl)bis(trifluoromethanesulfonyl)imide. J Polym Sci Part A Polym Chem50(16):3277–3285

67. Takada K, Fuchise K, Chen Y, Satoh T, Kakuchi T (2012) Controlled polymerization of methylacrylate for high-molecular-weight polymers by pentafluorophenylbis(triflyl)methane-pro-moted group transfer polymerization using triisopropylsilyl ketene acetal. J Polym Sci PartA Polym Chem 50(17):3560–3566

68. Fuchise K, Sakai R, Satoh T, Sato S-i, Narumi A, Kawaguchi S, Kakuchi T (2010) GroupTransfer Polymerization of N,N-Dimethylacrylamide Using Nobel Efficient System Consistingof Dialkylamino Silyl Enol Ether as an Initiator and Strong Brønsted Acid as an Organocatalyst.Macromolecules 43(13):5589–5594


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Organocatalytic Polymerization - Springer · Just after the proposal of organocatalysis, Hedrick...

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