Living Anionic Polymerization of Benzofulvene: Highly Reactive Fixed Transoid 1,3-Diene

Yuki Kosaka, Keita Kitazawa, Sotaro Inomata, and Takashi Ishizone*

ACS Macro Lett. 2013, 2, 164−167

Advisor : Professor Guey-Sheng Liou

Speaker : Yi-Chun Yeh

Date : 2014.12.26

Outline

• Author

• Anionic polymerization

• Living anionic polymerization

• Introduction

• Synthesis process

• SEC data

• Copolymerization

• Free radical & Anionic polymerization

• Concluding Remarks

1

Author• He was born in Saitama, Japan, in April, 1963.

• He received his M.S in polymer chemistry from Tokyo Institute of Technology in 1988 under supervision of Professors Seiichi Nakahama and Akira Hirao and started his academic career as Assistant Professor from 1989.

• After receiving doctorate degree in 1994, he spent a postdoctoral research at The University of Chicago with Professor P. E. Eaton on organic chemistry in 1995.

• Since 2000 he is Associate Professor of Department of Organic and Polymeric Materials at Tokyo Institute of Technology. His current research interests are centered on

synthesis of novel thermally-stable polymers possessing adamantyl groups

synthesis of novel water-soluble thermo-responsive polymers by means of living anionic polymerization.

Takashi Ishizone

石曽根 隆

2

Anionic polymerization

Anionic polymerization is a form of chain-growth polymerization or addition polymerization that involves the polymerization of vinyl monomers with strong electronegative groups.

A + CH2 CH

Y

BB CH2 CHA(n -1)CH2 CHX

CH2 CH

Yn

Y

3

This polymerization is carried out through a carbanion active species.

Anionic polymerizations are used in the production of polydiene synthetic rubbers, solution styrene/butadiene rubbers (SBR), and styrenic thermoplastic elastomers.

Anionic polymerization

4

Initiation by Electron Transfer

Initiation involve the transfer of an electron from the alkali metal to the monomer to form an anion-radical.

Initiation by Strong Anions

The initiation process involves the addition of a neutral (B:) or negative (B:-) nucleophile to the monomer.

Nucleophilic initiators include metal amides, alkoxides, and organometallic compounds (alkyllithium compounds and Grignard reagents).

The reactivity of initiators used in anionic polymerization should be similar to that of the monomer is the propagating species.

The least reactive monomers have the largest pKa values for their corresponding conjugate acid and thus, require the most reactive initiator.

Anionic polymerization characteristics that distinct from free radical polymerization :

Anionic polymerization

1. High selectivity of monomers2. Water can’t exist in the reaction system3. Polymerization rate fast, low activation energy, usually occurs in

low temperature4. Without termination or chain transfer

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By controlling the effects of counterion, solvent, temperature, Lewis base additives, and inorganic solvents, increase the potential of anionic polymerizations

Living Anionic polymerizationLiving polymerization of features: rapid initial, slow growth, no termination, no transfer reaction.

Monomer had been consumed, the anion remains active. Add new monomers, polymerization can continue; molecular weight increased with conversion in present, narrow molecular weight distribution; the end groups of the polymer, the composition, structure and molecular weight can be controlled.

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IntroductionFulvene (FV), C6H6 one of isomer of Benzene, show high reactivity toward various derivatives.

(strongly polarized!)

Possible to anionic polymerization

Fixed Transoid 1,3-Diene

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Nakano, T.; Yade, T.; Fukuda, Y.; Yamaguchi, T.; Okumura, S. Macromolecules 2005, 38, 8140−8148.

Nakano, T.; Yade, T.; Fukuda, Y.; Yamaguchi, T.; Okumura, S. Macromolecules 2005, 38, 8140−8148.

Only 1,2-addition!

Synthesis process

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SECTable 1. Anionic Polymerization of BF in THF at −78 °C for 1 ha

aYield 100%. ∼bMn(calcd) = (MW of monomer) × [M]/[I] + MW of initiator. cMn(obsd) was determined by SEC-RALLS equipped with refractive index (RI), light scattering (LS), and viscometer detectors.dMw/Mn was determined by SEC calibration using polystyrene standards in THF. eFor 15 h. fFor 20 h.

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Copolymerization

Scheme 1. Block Copolymerization of BF with Living Poly(MMA)

Poly(MMA) Poly(BF)

Poly(MMA)-block-poly(BF)

Poly(BF)-block-poly(MMA)

relative acidity of conjugated acid for indene (pKa = 20.1) is significantly higher than that of ethyl acetate (pKa = 24.4)

Anionic polymerizability of BF was remarkably high and comparable to that of MMA.

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Free radical & Anionic polymerization

Poly(BF-a)

Poly(BF-r)

Polymerization modes of BF and four possible diad units in poly(BF).

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Concluding Remarks

• we have succeeded in the living anionic polymerization of a novel exomethylene monomer, BF, to afford polymers with predicted molecular weights and narrow MWDs.

• The extremely high anionic polymerizability of this hydrocarbon is newly demonstrated and comparable to MMA.

• BF acts as a conjugated 1,3-diene to give only polymers containing the 1,2- and 1,4-addition modes.

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Thank you!

addition

陰離子聚合 自由基

1,2 76 % 19 %

1,4 24 % 81 %

addition

陰離子聚合 自由基

1,2 20 % 28 %

1,4 X 10 %

3,4 80 % 62 %

addition

陰離子聚合 自由基

1,2 41 % 9 %

1,4 59 % 91 %

12

3

4

1

23

4

1

2

3

4

對 diene來說 1,2加成和 1,4加成的介穩態是相同的，溫度提高，單體會有更多機會進行 1,4加成。 (動力學 )

而對此單體 2號為有大的立體障礙，所以 3、 4位置的雙鍵反應性較高。

考慮中間體的穩定性，對自由基來說2號位 (三級碳 )穩定，因此 1,2加成比例提高。除此之外，還要考慮動力學。

BF是上個單體環化後的結果，反而環外的 1、2位的雙鍵反應性較高。

，以 4n+2的規則來看，2號位的碳陰離子穩定性提高，而自由基反而穩定性下降，傾向 1,4加成。

須綜合考慮動力學及單體中間體的穩定性 (反應性 )