Anionic polymerization and copolymerization of p-bromostyrene

Monodispersed poly(4-bromostyrenes) (PBs) and their block copolymers with styrene, isoprene, and 3-methylbutene were prepared and characterized by GPC and NMR. Polystyryl and α-methylstyryl carbanions act as effective initiators of the anionic polymerization of Bs in THF. The undersirable side reactions, due to thermally or photochemically induced decomposition of the bromostyryl carbanions, PBs^?, may be eliminated by conducting the reaction at ?78°C and in the dark. Under such conditions, the rate constant of propagation, k_p (?78°), is 1.5 × 10³ M^?1 s^?1. Radical anions, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm Bs}^{\mathop - \limits_ \cdot} $\end{document}, formed as result of electron transfer from sodium naphthalenide to Bs, may eject spontaneously bromine ions. This step and reactions involving the respective phenyl radicals compete at ?78°C with the addition steps leading to polymer formation. Electron affinity of Bs seems to be much higher than that of styrene or isoprene, and PBs^? carbanions do not add to the latter monomers. Addition of Bs to polyisoprenyl carbanions leads to formation of the BsIBs block copolymers. BsIBs, prepared in THF, may be converted by preferential hydrogenation of the 1–2 adducts into block copolymers of Bs with poly(2-methylbutene) and isoprenyl segments. The effectiveness of Bs as a flame retarding constituent of polymeric systems seems to be much more pronounced when it is incorporated in a “block” than in a random fashion. A considerably larger fraction of PBs is required to achieve the same LOI value when the respective homopolymers are blended. Spatial distribution of the easily charred microdomains in the block copolymers is believed to be responsible for this phenomenon.     

Anionic polymerization and copolymerization of acrylophenone

The n-butyllithium-initiated polymerization of a mixture of acrylophenone (AP) and styrene produces only poly(AP), indicating that a chain ending in an AP enolate ion is not sufficiently nucleophilic to add to styrene. Radical copolymerization of AP and styrene yields a polymer containing 65% AP (at 41% conversion). In contrast, lithium dispersion-initiated polymerization of AP and styrene produces a product containing 50–99% AP, depending upon conversion. This observation is discussed in terms of current knowledge concerning alkali metal-initiated polymerization.     

Anionic polymerization of vinyl chloride

Anionic polymerization of vinyl chloride has been studied. Of the organometallic compounds tested as initiators, only butyllithium was found to initiate polymerization. Polymerization in bulk at 0°C and with tert-butyllithium as initiator gave poly(vinyl chloride) in a yield of 38% with M _n = 55,000. Tacticity of the anionic PVC was similar to that of conventional PVC prepared at similar temperatures. Anionic PVC was found to be less branched and more heat-stable than the conventional polymer.     

Anionic polymerization of propylene oxide

The anionic polymerization of propylene oxide with the use of potassium tert-butoxide and naphthalene sodium as initiator and dimethylsulfoxide, tetrahydrofuran and mixtures of both as solvent was investigated. The reactions were carried out in vacuum-sealed dilatometers over the temperature range 20?60°C. The products were analyzed by gelpermeation chromatography and infrared spectroscopy. The object of the investigation was to obtain information on the mechanism of the reaction and elucidate some of its kinetic aspects. It is shown that the polymerization occurs by two different processes depending on the experimental conditions: one involving free ions and ion-pairs, the other, ion-pairs alone. In the first case, where DMSO was used as solvent, the order of the reaction with respect to the initiator is greater than unity (～1.7), while in the second case, involving the mixture of DMSO and THF and ion-pairs alone, the reaction order is only one. Transfer to monomer is believed to take place only in the strongly dissociating DMSO medium, where free ions are present.     

Anionic polymerization and copolymerization of S-methyl thiomethacrylate

S-Methyl thiomethacrylate (methyl thiolmethacrylate, MTMA) was polymerized with a variety of anionic initiators such as n-BuLi, octylpotassium, PhMgBr, and Et₂AlNPh₂ in toluene and THF. Stereoregularity of the polymer (PMTMA) was determined from the ¹H-NMR spectrum of poly(methyl methacrylate), which had been derived from PMTMA, because the α-methyl resonance in the ¹H-NMR spectrum of PMTMA was not satisfactorily solved owing to the overlap of pentad signals. The ¹³C-NMR spectrum of PMTMA also showed the splitting due to pentad sequences. Stereoregularity of PMTMA was always low compared with that of poly(methyl methacrylate), which was prepared under the same reaction conditions. MTMA was much more reactive than methyl methacrylate and methacrylonitrile in the copolymerization with n-BuLi in toluene and in THF at ?78°C. The lower stereoregulation of the polymerization of MTMA and the higher reactivity of MTMA were mainly ascribed to the higher resonance effect of MTMA.     

Anionic polymerization and copolymerization of 1-cyanobutadiene

A stereospecific synthesis of trans-1-cyanobutadiene is described. This monomer was polymerized by n-butyl lithium in toluene and in tetrahydrofuran to yield sparingly soluble products. In both solvents, the concatenation was predominatly trans-1,4 with a little cis-1,4 and 3,4 content. Copolymers with methyl methacrylate and methyl pentadienoate were prepared in the same way: the reactivity ratios differed markedly in the two solvents being more nearly ideal in tetrahydrofuran.     

Anionic and coordination polymerization of 3-butyrolactone

Aluminoxane catalysts and anionic initiators can polymerize 3-butyrolactone, 3-BL, to high molecular weight stereoregular polymers. With the racemic monomer, [R,S]-3-BL, anionic polymerization with alkali metal complexes can form syndiotactic polymers and aluminoxane catalysts can form either highly isotactic, syndiotactic, or atactic poly-3-butyrolactone, P-3-BL, depending on the composition and method of preparation of the aluminoxane and the conditions of polymerization.     

Anionic and ionic coordinative polymerization of L-lactide

The potassium naphthalenide complex with 18-crown-6 is able to initiate anionic polymerization of L -lactide at 20°C. This type of anionic initiator does not have to be removed from the polymer as it does not affect metabolic processes. The ionic polymerization of L -lactide with an initiator based on Zn(II) acetyl acetonate, which is fairly stable, has been investigated. It has been found that this process leads to the corresponding polyesters, at high yields. © 1998 John Wiley & Sons, Ltd.     

Anionic polymerization of 1,2-butylene oxide

Anionic polymerizations of 1,2-butylene oxide were carried out in vacuum-sealed dilatometers in the range of 30–60°C. Potassium terbutoxide and dimsyl sodium were used as initiators; dimethyl sulfoxide (DMSO) and mixtures of DMSO with tetrahydrofuran were solvents. The polymer products were analyzed by gel permeation chromatography and infrared spectroscopy. The object of the investigation was to obtain information on the mechanism of the reaction and to elucidate some of its kinetic aspects. It has been shown that the polymerizations occur by two different processes, depending on the choice of experimental conditions. One of the processes involves free ions and ion-pairs, the other, ion-pairs alone. In the first case, where dimethyl sulfoxide is used as solvent, the order of the reaction with respect to the initiator concentration far exceeds unity (～1.8), while in the second case, involving mixed solvents, the order of the reaction, for all practical purposes, is one.     

Anionic polymerization of optically active oxiranes

The anionic bulk polymerization of optically active (2R, 3S)-3,4-epoxy-1,2-O-isopropylidenebutane-1,2-diol ( 1 ) and its (2 S, 3 S) diastereomer 2 was studied. Molecular weights and optical activity measurements as well as carbon and proton NMR spectra are reported. The polymers show solvent dependent inversion of the sign of optical rotation. The NMR spectra are consistent with isotactic polymer chains.     

Anionic polymerization of fluorine-substituted phenyl methacrylates

Synthesis and anionic polymerization of the fluorine-substituted phenyl methacrylates are herein reported.A series of mono-,di-,and multi-substituted fluorophenyl methacrylates H2C=C(CH3)C(O)OC6H4F-4(M1a),H2C=C(CH3)C(O)OC6H4F-3(M1b),H2C=C(CH3)C(O)OC6H3F2-2,4(M2),H2C=C(CH3)C(O)OC6H2F3-2,3,4(M3),H2C=C(CH3)C(O)OC6HF4-2,3,5,6(M4),and H2C=C(CH3)C(O)OC6F5(M5)were synthesized and characterized.Initially,the polymerization was carried out on the monomer M1a by using n Bu Li,t Bu Li,and KH as the respective catalysts;this approach produced the polymers in yields of12%–50%,but with lower molecular weights.Similar results were obtained by using t Bu Li for catalytically polymerizing the other five monomers.By introducing a co-catalyst Me Al(BHT)2,the catalysts Na H,Li H,and t Bu OLi each were tested to polymerize M1a,which gave the polymers in very low yields(3%–7%).Polymer yields of 13%–27%were obtained by each of the catalysts Li Al H4,n Bu Li,Ph Li,and t Bu Li in connection with Me Al(BHT)2,but a better yield(61%)was achieved with KH/Me Al(BHT)2.The KH/Me Al(BHT)2 catalyst system was further employed to polymerize M1b and M2,which afforded respective polymer yields of 12%–63%and 10%–53%,depending on the molar ratios of KH:Me Al(BHT)2 as well as on the monomer concentrations.All of the polymers produced were syndiotactically rich in structure,as indicated by either 1H or 19F NMR data.The polymerization mechanism by the combined catalyst system is proposed.     

Anionic ring-opening polymerization of silacyclobutane derivatives

Anionic polymerizations of 1,1-dimethylsilacyclobutane, 1,1-diethylsilacyclobutane and 1-methyl-1-phenylsilacyclobutane were investigated. Addition of 5 mol % of butyllithium to a solution of 1,1-dimethylsilacyclobutane in THF-hexane (1 : 1) at −48°C provided poly(1,1-dimethylsilabutane) in 99% yield. M_n and M_w/M_n of the obtained polymer were 2400 and 1.10. This polymerization proceeded with a living nature. M_n increased in proportion as the yield of polymer increased. Addition of the second fresh feed of the monomer to the reaction mixture restarted polymerization of the second monomer at the same rate as in the initial stage. Addition of styrene to the living poly(1,1-dimethylsilabutane) provided a poly(1,1-dimethylsilabutane-b-styrene) block copolymer. It was also found that a polymerization of 1,1-diethylsilacyclobutane in THF-hexane at −48°C showed a living nature. In contrast, a polymerization of 1-methyl-1-phenylsilacyclobutane in THF at −78°C did not show a living nature. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3207–3216, 1997     

Anionic polymerization of a fluorinated butadiene

1,1-Bis(trifluoromethyl)-1,3-butadiene (I) is cleanly prepared in three steps. I produces an amorphous polymer by free-radical catalysis. Crystalline poly-I is produced by butyllithium catalysis in tetrahydrofuran at ?78°C. Qualitative kinetic experiments indicate that the anionic polymerization proceeds by a “living polymer” process. An AB block copolymer may be formed by adding I to anionically propagating butadiene; however, the reverse does not occur.     

Anionic and cationic polymerization of norbornadiene in hydrocarbon

Norbornadiene (NBD) has been successfully polymerized in benzene solvent in high yield (up to 100%) using AlCl₃ as initiator. Anionic polymerization of the same compound was achieved using butyllithium as initiator. According to the IR and NMR data, both polymers have a 2,6-disubstituted nortricyclene structure. The cationic polymerization gave an amorphous polymer; the anionic polymerization resulted in the formation of a crystalline product showing higher stability.     

Anionic polymerization with expansion in volume

New bicyclic and tricyclic compounds have been synthesized by the Lewis acid-catalyzed condensation of epoxides with cyclic acid anhydrides or cyclic bislactones. These materials take part in the anionic addition polymerization of amine-functional polyamides with diepoxides, and modify the shrinkage that is characteristic of the reaction. It is possible to control the extent of shrinkage by choosing an appropriate comonomer and by adjusting the concentration of this material in the reaction mixture.