“Group-transfer” copolymerization

Çatalgil, Huceste H.; Jenkins, A. D.

doi:10.1016/0014-3057(91)90151-d

Cited by 17 publications

(2 citation statements)

References 2 publications

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“…Other GTP experiments could be implemented to support the occurrence of the associative mechanism in particular, the determination of the activation energy and entropy of the polymerization by varying the temperature. − This will be the scope of a subsequent publication.…”

Section: Resultsmentioning

confidence: 99%

Group Transfer Polymerization of (Meth)acrylic Monomers Catalyzed by N-Heterocyclic Carbenes and Synthesis of All Acrylic Block Copolymers: Evidence for an Associative Mechanism

2009

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N-Heterocyclic carbenes (NHCs), namely, 1,3-bis-(diisopropyl)imidazol-2-ylidene (1) and 1,3-bis(di-tert-butyl)imidazol-2-ylidene (2) were employed as neutral organocatalysts to bring about the group transfer polymerization (GTP) of both methacrylic and acrylic monomers, including methyl methacrylate (MMA), tert-butylacrylate (tBA), and n-butylacrylate (nBA). This could be achieved at room temperature using 1-methoxy-2-methyl-1-trimethylsiloxypropene (MTS) as initiator in polar or apolar medium. In this way, polymethacrylates and polyacrylates with molar masses in the range 10 000-300 000 g 3 mol -1 , corresponding to the initial [monomer]/[MTS] ratio and with polydispersities lower than 1.2, were obtained in quantitative yields. The kinetics of GTP of MMA catalyzed by 1 or 2 was further investigated. Though the first-order kinetic plot ln[M] 0 /[M] versus time deviated from linearity at high monomer conversion, no inhibition period was noted at low monomer conversion. Moreover, the polymerization rate dramatically increased as the concentration of initiator increased, with first-order dependence in initiator. When mixed in 1/1 molar ratio, MTS and NHC 1 did not reveal the formation of enolate-type species by 29 Si or 13 C NMR spectroscopy. Based on these observations, we propose that NHCs activate the silyl ketene acetal initiator and further propagate GTP via an associative mechanism. The fact that ln[M] 0 /[M] does not evolve linearly with time in the terminal phase of the polymerization can be understood by a reduced diffusion of the catalyst to the trimethylsilyl end groups. The proposed associative mechanism can also account for the successful control of NHC-catalyzed GTP of acrylates during which termination reactions such as backbiting or internal isomerization could be drastically minimized. Next, was described the synthesis of all acrylic block copolymers based on polyacrylates and polymethacrylates (e.g., PMMA-b-PnBA-b-PMMA), utilizing the same NHC as catalyst in sequential GTP. It is again argued that such block copolymer formation is favored by an associative mechanism forming highly unstable activated silicon intermediates.

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Section: Resultsmentioning

confidence: 99%

Group Transfer Polymerization of (Meth)acrylic Monomers Catalyzed by N-Heterocyclic Carbenes and Synthesis of All Acrylic Block Copolymers: Evidence for an Associative Mechanism

2009

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“…One such technique, developed by Kelen and Tiid&, and known as the extended Kelen-Tiid& method (EKT), is a linear method based on the suggestions of Walling and Briggs, that remains almost constant during the reaction [14][15][16][17]. EKT is the exact solution for ideal copolymerization.…”

Section: Introductionmentioning

confidence: 99%

Allyl reactivity in group transfer copolymerization

Öncül-Koç¹,

Çatalgil‐Giz²

1995

Macro Chemistry & Physics

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Statistical copolymers of allyl methacrylates with methyl and ethyl methacrylates are synthesized. Moderate conversions are used. Reactivity ratios are calculated by linearised methods which take composition drift into account as well as by non‐linear least‐squares approximation. For the allyl methacrylate/methyl methacrylate system, rallyl values obtained by various methods are between 1,62 and 1,60 and rmethyl values between 0,36 and 0,34. For the allyl methacrylate/ethyl methacrylate system, rallyl values are between 1,37 and 1,16 and rethyl values between 0,40 and 0,47.

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Molecular Engineering of Side Chain Liquid Crystalline Polymers by Living Polymerizations

Pugh¹,

Kiste²

1998

Handbook of Liquid Crystals Set

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Living" anionic, cationic, metalloporphyrin and ring-opening metathesis polymer izations have been used to prepare well-defined side-chain liquid crystalline homopolymers, block and graft copolymers and statistical copolymers. This paper analyzes their successes and failures by reviewing the mechanistic aspects and experimental conditions of each type of polymerization, and identifies other classes of mesogenic monomers that could be polymerized in a controlled manner in the future. The emerging structure/property relationships are then identified using well defined SCLCPs in which only one structural feature is varied while all others remain constant. The the:rmal transitions of liquid crystalline polymethacrylates, polynorbomenes and poly(vinyl ether)s reach their limiting values at less than 50 repeat units, which are generally equal to those of the corresponding infinite molecular weight polymers:Increasing spacer length depresses the glass transition of SCLCPs, and consequently often uncovers mesophases that are not observed without a spacer. The crystalline melting of tactic SCLCPs also tends to decrease (with odd-even alternation) with increasing spacer length. Without additional order within the polymer backbone due to high tacticity, mesogenic side-chains generally do not crystallize until the spacer contains at least nine carbon atoms. As the flexibility of the polymer backbone increases, the glass transition temperature decreases, and the side chains are able to crystallize at shorter spacer lengths and form more

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“Group-transfer” copolymerization

Cited by 17 publications

References 2 publications

Group Transfer Polymerization of (Meth)acrylic Monomers Catalyzed by N-Heterocyclic Carbenes and Synthesis of All Acrylic Block Copolymers: Evidence for an Associative Mechanism

Group Transfer Polymerization of (Meth)acrylic Monomers Catalyzed by N-Heterocyclic Carbenes and Synthesis of All Acrylic Block Copolymers: Evidence for an Associative Mechanism

Allyl reactivity in group transfer copolymerization

Molecular Engineering of Side Chain Liquid Crystalline Polymers by Living Polymerizations

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