Butyllithium polymerization

Thiophene, bromotetrahydromethyl-pyrolysis, 3, 902 Thiophene, 5-t-butyl-2-methyl-dealkylation, 4, 800 Thiophene, chloro-polymerization, 4, 758 reaction with n-butyllithium, 4, 831 synthesis, 4, 835, 882, 933 Thiophene, 2-chloromercurio-reactions... 

Many initiators, such as alkyl and aryllithium and sodium and lithium suspensions in liquid ammonia, effect the polymerization. For example, acrylonitrile combined with n-butyllithium forms a carbanion intermediate ... 

Currently, more SBR is produced by copolymerizing the two monomers with anionic or coordination catalysts. The formed copolymer has better mechanical properties and a narrower molecular weight distribution. A random copolymer with ordered sequence can also be made in solution using butyllithium, provided that the two monomers are charged slowly. Block copolymers of butadiene and styrene may be produced in solution using coordination or anionic catalysts. Butadiene polymerizes first until it is consumed, then styrene starts to polymerize. SBR produced by coordinaton catalysts has better tensile strength than that produced by free radical initiators. 

If desired, the potassium salt can be converted into the allyllithium derivative by metal exchange with lithium bromide46. Butyllithium/potassium 2,2,6,6-tetramethylpiperidide depro-tonates isoprene without polymerization to give 2-methylene-3-butenyllithium47. 

The addition of a cyclic vinyl sulfoxide anion to aldehydes has been reported only once14. Interestingly, 2,3,4,5-tetrahydro-l//-thiepane S-oxide cannot be metalated by lithium diiso-propylamide in tetrahydrofuran at — 78 °C. At higher temperatures ( — 20° to 0°) a white polymeric precipitate is formed. This polymeric product is also formed when the sulfoxide is treated with butyllithium or. wr-butyllithium in tetrahydrofuran even at — 78 C. However, metalation can be accomplished with. sec-butyllithium using an excess of N,N,N, N -tetramcthylethylenediamine in tetrahydrofuran at —78 C. In this case, a pale yellow solution is formed immediately and upon addition of benzaldehydc instantaneous dccolorization occurs yielding a mixture of diastereomeric alcohols in 90% yield. 

Reaction Mechanism. The reaction mechanism of the anionic-solution polymerization of styrene monomer using n-butyllithium initiator has been the subject of considerable experimental and theoretical investigation (1-8). The polymerization process occurs as the alkyllithium attacks monomeric styrene to initiate active species, which, in turn, grow by a stepwise propagation reaction. This polymerization reaction is characterized by the production of straight chain active polymer molecules ("living" polymer) without termination, branching, or transfer reactions. 

The effect of media viscosity on polymerization rates and polymer properties is well known. Analysis of kinetic rate data generally is constrained to propagation rate constant invarient of media viscosity. The current research developes an experimental design that allows for the evaluation of viscosity dependence on uncoupled rate constants including initiation, propagation and macromolecular association. The system styrene, toluene n-butyllithium is utilized. 

Syntheses. Isotactic poly(methyl methacrylate) was synthesized by the method of Tsuruta et al. (9 ). Under a nitrogen atmosphere, a quantity of 6 mL (0.056 mole) of methyl methacrylate (MMA) dried over 4A molecular sieve was dissolved in 24 mL of similarly dried toluene. To the glass vial containing the reaction was added 0.65 mL of 1.6 M n-butyllithium, and the reaction was kept at -78°C in a dry ice/isopropanol bath. The polymerization was halted 24 hr later with the addition of hydrochloric acid and methanol (methanol/water 4.1 by volume). The polymer was dried in vacuo at 50°C, redissolved in methylene chloride, precipitated by being poured into water-containing methanol, and dried in vacuo at 50°C. Tacticlty and composition were verified with % NMR. Yield 47%. 

However, vinyltin monomers are readily polymerized or copolymerized with butyllithium at 0 and 20 °C respectively by an anionic mechanism51). 

Symmetric triblock copolymers P4VP-fr-PBd-fo-P4VP were prepared using a difunctional initiator derived from the reaction of m-diisopropenylbenzene with f-butyllithium at - 20 °C (Scheme 9) [27]. The synthesis was conducted in a mixture of toluene and THF at temperatures higher than room temperature for the polymerization of Bd, followed by a lowering of the temperature at - 78 °C and finally addition of an extra quantity of THF and 4VP. The 4VP content was kept lower than 30% to avoid problems arising from the poor sol-... 

Hyperbranched polymers have also been prepared via living anionic polymerization. The reaction of poly(4-methylstyrene)-fo-polystyrene lithium with a small amount of divinylbenzene, afforded a star-block copolymer with 4-methylstyrene units in the periphery [200]. The methyl groups were subsequently metalated with s-butyllithium/tetramethylethylenediamine. The produced anions initiated the polymerization of a-methylstyrene (Scheme 109). From the radius of gyration to hydrodynamic radius ratio (0.96-1.1) it was concluded that the second generation polymers behaved like soft spheres. 

Mixtures of hexamethyldisilazane, /z-butyllithium, and dimethylzinc reacted, Scheme 55, with the formation of a lithium zincate 70. In the solid state, Figure 37, 70 consists of four-membered, -symmetric LiN2Zn rings, which form a polymeric structure through bridging methyl groups from zinc to lithium.126... 

A bulky methacrylate, triphenylmethyl methacrylate (TrMA), is a unique monomer which gives an almost 100% isotactic polymer in anionic polymerization with n-butyllithium both in nonpolar and polar solvents. Moreover, even free-radical polymerization affords a highly isotactic polymer from this monomer.23 The isotactic specificity of TrMA polymerization is ascribed to the helical formation of the main chain. When TrMA is polymerized in toluene at —78°C... 

In 1866 AD a polymeric product was formed from styrene and sulphuric acid. Another breakthrough was the production of synthetic rubber from butadiene by using metallic sodium or potassium by German scientists during 1911 -22. In 1929, Ziegler reported polymerisation of vinyl monomers using butyllithium. 

The masked disilene strategy was also successfully applied to the synthesis of dialkylamino-substituted polysilanes,60 61 63 by the -butyllithium-initiated polymerization of dialkylamino-substituted phenyldisilabicycloocta-dienes, as shown in Scheme 23. 

The synthesis and characterization of a series of dendrigraft polymers based on polybutadiene segments was reported by Hempenius et al. [15], The synthesis begins with a linear-poly(butadiene) (PB) core obtained by the sec-butyllithium-initiated anionic polymerization of 1,3-butadiene in n-hexane, to give a microstructure containing approximately 6% 1,2-units (Scheme 3). The pendant vinyl moities are converted into electrophilic grafting sites by hydrosilylation with... 

Braun et al. [258] used a combination of tert-butyllithium (t-BuLi) and tetramefhy-lethylenediamine to create initiator sites at the surface of carbon black for the LASIP of styrene. Schomaker et al. [259] first immobilized a methyl methacrylate derivative on colloidal silica and after activation by a Grignard reagent polymerized MMA. 

Polymerization in electrostatic systems like the ones mentioned above is stericaUy inhibited by alkyl substitution at the a-carbon which must assume a coordination number greater than 4. Coates and Glockhng have treated this inhibition of polymerization in terms of decreased electronegative character of the branched alkyl groups. Therefore, stimulated by the idea that f-afkylhthium compounds may exist as low polymers or even as monomeric molecules, Weiner and coworkers and Kottke and Stalke have isolated f-butyllithium as a pure substance for the first time and characterised it by spectroscopic methods and X-ray diffraction. The colourless crystalline solid was found to be tetrameric over a range of concentrations in both benzene and hexane ... 

It was already established that pure ethyl-" " and f-butyllithium exist as six- and fourfold polymers, respectively, in benzene solution. Apparently, C—Li bond cleavage takes place in this solvent leading to an exchange of alkyl groups between polymeric organo-lithium molecules when both compounds are present. The products are believed to be electron-deficient polymers of the type (EtLi) (f-BuLi) , wha-e m is a small number such as 4 or 6. ... 

Methyl sorbate and analogous monomers were polymerized in the presence of (/ )-2-methylbutyllithium or of complexes between butyllithium and optically active Lewis bases (329, 330) (see formulas 32 and 33) the polymers show weak optical activity. The prevailing configuration of the — CH(CH3)— group was determined by the sign of rotation of the methylsuccinic acid obtained from the polymer after ozonization. The low optical purity ( = 6%) found is related to the presence of a remarkable stereochemical disorder (115, 116) and to the fact that the chiral agent is active, at least in the case of methylbutyllithium, only in the initiation reaction. 

Another result of great importance—the conformational asymmetric polymerization of triphenylmethyl methacrylate realized in Osaka (223, 364, 365)— has already been discussed in Sect. IV-C. The polymerization was carried out in the presence of the complex butyllithium-sparteine or butyllithium-6-ben-zylsparteine. The use of benzylsparteine as cocatalyst leads to a completely soluble low molecular weight polymer with optical activity [a]o around 340° its structure was ascertained by conversion into (optically inactive) isotactic poly(methyl methacrylate). To the best of my knowledge this is the first example of an asymmetric synthesis in which the chirality of the product derives finom hindered rotation around carbon-carbon single bonds. 

Synthetic cA-l,4-polyisoprene (structure 5.42) is produced at an annual rate of about 100,000 t by the anionic polymerization of isoprene when a low dielectric solvent, such as hexane, and K-butyllithium are used. But, when a stronger dielectric solvent, such as diethy-lether, is used along with w-butyllithium, equal molar amount of tra i -l,4-polyisoprene and cA-3,4-polyisoprene units is produced. It is believed that an intermediate cisoid conformation assures the formation of a cis product. An outline describing the formation of cA-1,4-polyisoprene is given in structure 5.42. 

Which of the following could be used to initiate the polymerization of isobutylene (a) sulfuric acid, (b) boron trifluoride etherate, (c) water, or (d) butyllithium ... 

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