Use of cryptates in anionic polymerization. I. Anionic activation

Boileau, Sylvie; Kaempf, B.; Lehn, J.‐M.; Schué, François

doi:10.1002/pol.1974.130120405

Cited by 57 publications

(8 citation statements)

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“…These macrobicyclic ligands (I) discovered by Lehn These complexes lead to a considerable increase of the interionic distance in the ion pairs and it has been shown that such ligands have a marked activating effect on anionic polymerizations (14,15,16). Moreover, the aggregates are destroyed and simple kinetic results have been obtained in the case of propylene sulfide and ethylene oxide polymerizations (12).…”

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confidence: 97%

Anionic Polymerization of Cyclosiloxanes with Cryptates as Counterions

Boileau

1985

ACS Symposium Series

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The anionic polymerization of cyclosiloxanes was examined in benzene and toluene with lithium cryptates as counterions. Only one type of active species is observed in the case of Li + + [211]; thus, the kinetics of the propagation and of the by-product cyclosiloxanes formation can be studied in detail for the first time. The reactivity of cryptated silanolate ion pairs toward the ring opening of D 3 is greatly enhanced compared to that of other systems. The amount of cyclic by-products is very low when the polymer yield reaches the maximum value. PDMS of narrow molecular weight distributions were obtained using a cryptand larger than the [211].The anionic polymerization of cyclosiloxanes has been studied for a long time. However the knowledge of the mechanism of the process is still unfortunately rather limited (1^2) · This is partially due to the fact that the polymerization is of the equilibrium type and besides linear polymers, cyclic structures exist in solution. It has been shown that under certain conditions, hexamethylcyclotrisiloxane (D3) polymerizes to give linear polymers of negligible cyclosiloxane content and of narrow molecular weight distribution at a much more rapid rate than octamethylcyclotetra siloxane (D4) (3)· This can be explained by the ring strain of D3 which enhances the reactivity of the Si-0 bonds. A suitable initiator such as butyllithium can be mixed with D3 in hydrocarbon solvents to form Bu(-Si (CH3)2 _ 0)3Li (4). No polymerization occurs even in the presence of excess D3 until a donor solvent like THF (3,5), diglyme (6), triglyme (5), DME (7^), HMPA (7) or DMSO (3) is added; then a reasonably rapid polymerization starts to give near monodisperse polymers.Only few kinetic investigations have been performed on these systems though the side reactions which involve intra and intermolecular attacks of the chains by living centers can be neglected in the first stage of polymerization (5,7). The nature of the active propagating species as well as their relative proportion is

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confidence: 97%

Anionic Polymerization of Cyclosiloxanes with Cryptates as Counterions

Boileau

1985

ACS Symposium Series

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“…It is also well known that cryptands such as (I) complex cationic species very strongly and hence promote nucleophilic reactionsY Several studies on the polymerization using such complexing agents have been reported. 13 …”

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Homogeneous Polymerization of Methyl Methacrylate Initiated by Potassium Salts of Methanol and t-Butyl Alcohol in the Presence of Cryptand [222]

Viguier

Collet

Schué

1982

Polym J

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ABSTRACT:Homogeneous polymerization of methyl methacrylate initiated by potassium salts of methanol and t-butyl alcohol was studied in toluene in the presence of cryptand [222). The polymers prepared were predominantly syndiotactic. The isotacticities increased slightly with an increase in temperature. More than thirty years ago, it was claimed that alkali metal salts of primary alcohols could not initiate the polymerization of methyl methacrylate (MMA) in ether.' More recently, the oligomerization of MMA by CH 3 0-jCH 3 0H solutions has been studied.Z· 3 Oligomers having a degree of polymerization up to six were isolated and characterized. Initiation proceeded by the addition of CH 3 0-to the double bond, and termination by protonation from the methanol.t-Alkoxides, n-butoxides, derivatives of poly(ethylene oxide) of alkali metals as well as ethylmagnesium alkoxides for the initiation of the homogeneous polymerization of methacrylic acid esters have been described in previous papers. 4 -10 It has also been shown that the polymerization of MMA by alkali metal salts of 2-methoxyethanol and like compounds can be carried out in aprotic dipolar solvents such as hexamethylphosphoramide, dimethyl sulfoxide, and dimethylacetamide." Polymerization was greatly promoted by these solvents, even when in small quantities. It is also well known that cryptands such as (I) complex cationic species very strongly and hence promote nucleophilic reactionsY Several studies on the polymerization using such complexing agents have been reported. 13 _,In this paper, we report on the homogeneous polymerization of MMA in toluene by potassium salts of methanol and t-butyl alcohol in the presence of cryptand (1). It was accepted, according to our previous communication, 17 that such complexing agents increase the reactivity of the alkoxide. (Potassium methoxide and t-butoxide are noted respectively MeOK and t-BuOK.) EXPERIMENTAL MaterialsThe purification of toluene and MMA as well as the experimental techniques are described elsewhere.17 Potassium salts of the alcohols were prepared by the reaction of potassium metal with an excess of alcohol in toluene followed by removing solvent and alcohol under vacuum at 100°C during at least 15 hours. This gave the alkoxides as snow-137

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“…Furthermore, the use of cryptands or crown ethers as catalysts has been reported [ 12 ], mainly for the AROP of heterocyclic monomers such as ethylene oxide, cyclosiloxanes, lactones etc. [ 13 , 14 , 15 , 16 ], but also for the anionic polymerization of styrene, butadiene, isoprene and methyl methacrylate [ 17 , 18 , 19 , 20 ]. These compounds form exceptionally stable cation inclusion complexes, in which the cation is completely surrounded by the ligand and hidden inside the molecular cavity.…”

Section: Introductionmentioning

confidence: 99%

“…This leads to a high increase of the interionic distance in the ion pairs, resulting in higher polymerization rates, due to the suppression of the association between ion pairs in non-polar media [ 21 ]. Additionally, when the polymerization of dienes in non-polar solvent was performed in the presence of cryptands, high reaction rates were observed alongside with high vinyl content (up to 75%) [ 17 , 18 ].…”

Section: Introductionmentioning

confidence: 99%

Anionic Polymerization of Styrene and 1,3-Butadiene in the Presence of Phosphazene Superbases

et al. 2017

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Abstract:The anionic polymerization of styrene and 1,3-butadiene in the presence of phosphazene bases (t-BuP 4 , t-BuP 2 and t-BuP 1 ), in benzene at room temperature, was studied. When t-BuP 1 was used, the polymerization proceeded in a controlled manner, whereas the obtained homopolymers exhibited the desired molecular weights and narrow polydispersity (Ð < 1.05). In the case of t-BuP 2 , homopolymers with higher than the theoretical molecular weights and relatively low polydispersity were obtained. On the other hand, in the presence of t-BuP 4 , the polymerization of styrene was uncontrolled due to the high reactivity of the formed carbanion. The kinetic studies from the polymerization of both monomers showed that the reaction rate follows the order of Furthermore, the addition of t-BuP 2 and t-BuP 1 prior the polymerization of 1,3-butadiene allowed the synthesis of polybutadiene with a high 1,2-microstructure (~45 wt %), due to the delocalization of the negative charge. Finally, the one pot synthesis of well-defined polyester-based copolymers [PS-b-PCL and PS-b-PLLA, PS: Polystyrene, PCL: Poly(ε-caprolactone) and PLLA: Poly(L-lactide)], with predictable molecular weights and a narrow molecular weight distribution (Ð < 1.2), was achieved by sequential copolymerization in the presence of t-BuP 2 and t-BuP 1 .

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Use of cryptates in anionic polymerization. I. Anionic activation

Cited by 57 publications

References 9 publications

Anionic Polymerization of Cyclosiloxanes with Cryptates as Counterions

Anionic Polymerization of Cyclosiloxanes with Cryptates as Counterions

Homogeneous Polymerization of Methyl Methacrylate Initiated by Potassium Salts of Methanol and t-Butyl Alcohol in the Presence of Cryptand [222]

Anionic Polymerization of Styrene and 1,3-Butadiene in the Presence of Phosphazene Superbases

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