Anionic polymerization of methyl (propyl) cyclosiloxanes

Yuzhelevskii, Yu. A.; Kagan, Ye.G.; Timofeyeva, N.P.; Doletskaya, T.D.; Klebanskii, A. L.

doi:10.1016/0032-3950(71)90238-3

Cited by 8 publications

(7 citation statements)

References 5 publications

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“…The next factor that has a significant effect on the course of polymerization is the nature of the organic groups at the silicon atoms of siloxane cyclosiloxanes. The introduction of electron-donating substituents-longer hydrocarbons than the methyl group-reduces the rate of anionic polymerization of cyclosiloxane, while electron-withdrawing substituentsalkenyl, aromatic, phenyl, 3,3,3-trifluoropropyl or cyanoalkyl groups-increase the rate of polymerization [82][83][84]. In this case, electron-withdrawing substituents at the silicon atom during anionic polymerization lead to the formation of a siloxanolate anion with a lower nucleophilic activity, which somewhat levels out the increase in the activity of cycles during polymerization.…”

Section: Influence Of the Structure Of The Initial Organocyclosiloxan...mentioning

confidence: 99%

Ring-Opening Polymerization (ROP) and Catalytic Rearrangement as a Way to Obtain Siloxane Mono- and Telechelics, as Well as Well-Organized Branching Centers: History and Prospects

et al. 2022

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PDMS telechelics are important both in industry and in academic research. They are used both in the free state and as part of copolymers and cross-linked materials. At present, the most important, practically used, and well-studied method for the preparation of such PDMS is diorganosiloxane ring-opening polymerization (ROP) in the presence of nucleophilic or electrophilic initiators. In our brief review, we reviewed the current advances in the field of obtaining polydiorganosiloxane telechelics and monofunctional PDMS, as well as well-organized branching centers by the ROP mechanism and catalytic rearrangement, one of the first and most important reactions in the polymer chemistry of silicones, which remains so at the present time.

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Section: Influence Of the Structure Of The Initial Organocyclosiloxan...mentioning

confidence: 99%

Ring-Opening Polymerization (ROP) and Catalytic Rearrangement as a Way to Obtain Siloxane Mono- and Telechelics, as Well as Well-Organized Branching Centers: History and Prospects

et al. 2022

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“…The activation energy of the anionic polymerization of D 4 initiated by potassium siloxanolate without any promoter is 81.5 kJ mol À1 . 9,10 The other is when the C p /C i ratio is not more than 1.0, the difference of ''k'' between the reaction with C p /C i ¼ 1.0 and that with C p /C i ¼ 0.33, with the value of 3.0 (k 1 /k 2 ), is identical for each promoter.…”

Section: Kinetics Of the Polymerization Of Dmentioning

confidence: 94%

Kinetics of the anionic ring‐opening polymerization of octamethylcyclotetrasiloxane initiated by potassium isopropoxide

Zhang

Wang

et al. 2006

J of Applied Polymer Sci

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Kinetics of the anionic ring-opening polymerization of octamethylcyclotetrasiloxane (D 4 ) in bulk initiated by potassium isopropoxide was studied. Several promoters including N-methyl-2-pyrrolidinone (NMP), N,Ndimethylformamide (DMF), and diglyme were used. It is indicated that the reactions are first-order in D 4 during the initial stage of polymerization. The polymerization rate of D 4 is influenced by a number of factors, such as the nature of promoters, the molar ratio of promoter to initiator (C p /C i ratio), and the reaction temperatures. With the use of NMP as promoter, the polymerization rate constant at 308C is 10.482 h À1 with the C p /C i ratio equal to 3.0. As the C p /C i ratio increases, the polymerization rate constant increases sharply and the cyclic oligomers content in polymer decreases evidently. The back-biting reaction that leads to the formation of decamethylcyclopentasiloxane (D 5 ) occurred in the polymerization of D 4 . The rate of the D 5 formation relatively to the rate of D 4 conversion increases with the conversion of D 4 .

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“…To overcome the shortcomings of the equilibrium polymerization, many efforts have been put to study the non-equilibrium polymerization. 16,18,[22][23][24][25][26][27][28][29][30] Yuzhelevskii and coworkers [22][23][24][25] studied the effect of promoters like aprotic and polar solvents including dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), and organic phosphates on D 3 F polymerization and found that the polymerization rate could be increased by at least two orders of magnitude by promoting the dissociation of ion pairs between SiO À and Li + . Veith et al 16 investigated the effect of the DMSO/ butyllithium (BuLi), promoter-initiator (P-I) combination on the polymerization of D 3 F at 40 C indicating that the initiator containing lithium ion instead of sodium ion could remarkably reduce the rate of backbiting reaction.…”

Section: Introductionmentioning

confidence: 99%

Controlled synthesis and characterization of poly[methyl(3,3,3-trifluoropropyl)siloxane] with selective end groups

et al. 2014

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Anionic ring-opening polymerization of 1,3,5-tris(trifluoropropylmethyl)cyclotrisiloxane in the bulk was studied using dilithium diphenylsilanediolate as an initiator (I); and N,N-dimethylformamide (DMF), bis(2-methoxyethyl)ether (Diglyme), and 1,2-dimethoxyethane (DME) as promoters (P). A detailed study on the kinetics of polymerization with different molar ratios of promoter to initiator ([P]/[I]) that were equal to 2.0, 4.0, and 6.0 revealed that the yield of linear polymers was the highest when [P]/[I] ¼ 2.0 for all the promoters, among which DME was the most efficient promoter for suppressing the backbiting reactions. The reaction promoted by DME had a very broad "termination window" with the highest yield of linear polymer and very narrow molar mass distribution. The results of the matrix-assisted laser desorption/ionization time of flight mass spectrometry indicated that the intermolecular redistribution occurred during the process of polymerization. PMTFPS with end groups such as vinyl, hydroxyl, hydrogen and chloromethyl were prepared and characterized by 1 H NMR, 29 Si NMR and FT-IR. Polymers having vinyl end groups displayed higher thermo stability than those having hydroxyl end groups under nitrogen.

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Anionic polymerization of methyl (propyl) cyclosiloxanes

Cited by 8 publications

References 5 publications

Ring-Opening Polymerization (ROP) and Catalytic Rearrangement as a Way to Obtain Siloxane Mono- and Telechelics, as Well as Well-Organized Branching Centers: History and Prospects

Ring-Opening Polymerization (ROP) and Catalytic Rearrangement as a Way to Obtain Siloxane Mono- and Telechelics, as Well as Well-Organized Branching Centers: History and Prospects

Kinetics of the anionic ring‐opening polymerization of octamethylcyclotetrasiloxane initiated by potassium isopropoxide

Controlled synthesis and characterization of poly[methyl(3,3,3-trifluoropropyl)siloxane] with selective end groups

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