Anionic Polymerization Of Vinyl Monomers Research Articles

Living anionic polymerization of vinyl monomers using benzyltrimethylsilane‐metal alkoxide initiator systems

AbstractWell controlled living anionic polymerization of vinyl monomers was achieved by using the initiator system composed of desilylation of benzyltrimethylsilane (BnTMS) by potassium tert‐butoxide (t‐BuOK) in tetrahydrofuran and trapping the resulting benzyl anion with α‐methylstyrene or 1,1‐diphenylethylene in the initiator system in order to control the desilylation and polymerization reaction. This method led to high initiation efficiency and strict control of molecular weights of the obtained polymers. Furthermore, the initiator system could be applied to the synthesis of a block copolymer of PMMA‐b‐PtBMA. These results showed that living nature of the polymer obtained using BnTMS/t‐BuOK initiator system in the presence of the appropriate additives.

Benzylsilane-metal alkoxide initiator systems for anionic polymerization of vinyl monomers

Benzylsilane-metal alkoxide initiator systems for anionic polymerization of vinyl monomers

Quo Vadis Carbanionic Polymerization?

Living anionic polymerization will soon celebrate 70 years of existence. This living polymerization is considered the mother of all living and controlled/living polymerizations since it paved the way for their discovery. It provides methodologies for synthesizing polymers with absolute control of the essential parameters that affect polymer properties, including molecular weight, molecular weight distribution, composition and microstructure, chain-end/in-chain functionality, and architecture. This precise control of living anionic polymerization generated tremendous fundamental and industrial research activities, developing numerous important commodity and specialty polymers. In this Perspective, we present the high importance of living anionic polymerization of vinyl monomers by providing some examples of its significant achievements, presenting its current status, giving several insights into where it is going (Quo Vadis) and what the future holds for this powerful synthetic method. Furthermore, we attempt to explore its advantages and disadvantages compared to controlled/living radical polymerizations, the main competitors of living carbanionic polymerization.

Precise Synthesis of Functional Block Copolymers by Living Anionic Polymerization of Vinyl Monomers Bearing Nitrogen Atoms in the Side Chain

Precise synthetic methods to prepare functional block copolymers with heteroatoms (nitrogen, oxygen, sulfur, phosphorous, halogen, etc.) have received much attention for the fabrication of practical nanomaterials. Specifically, well‐defined materials containing nitrogen‐based functional groups show unique electrical, optical, and amphiphilic properties. To synthesize these products, living anionic polymerization is the most powerful method. However, the disruption of undesirable reactions is considered to be a great challenge in the anionic polymerization of functional monomers with heteroatoms. To overcome these problems, facile methods such as polymerization at low temperature, careful choice of additives and initiators, and the introduction of protective groups can be used. In this review, recent advances in the anionic polymerization of vinyl monomers with triphenylamine, carbazole, and pyridine moieties in the side chains will be discussed. Also covered is the morphological control of these polymers to obtain well‐defined block copolymers for practical applications such as organic memory devices and light emitting diodes. image

ChemInform Abstract: Star‐Shaped Polymers with the Fullerene C60 Branching Center

AbstractReview: syntheses, functionalization and properties; 92 refs.

Star-shaped polymers with the fullerene C60 branching center

The anionic methods for the synthesis of homo- and heteroarm (hybrid) star-shaped polymers using fullerene C60 aPre considered. The possibilities of fullerene C60 as an agent of combination of living polymer chains and the procedures of transformation of polymer derivatives of C60 (hexaadducts) into polyfunctional macroinitiators of anionic polymerization of vinyl monomers are shown. The methods for functionalization of polymer fullerene derivatives and their combinations into structures of complex controlled architecture are presented. The structural features and initiating properties of the living polymer fullerene derivatives and their role in the formation of heteroarm star-shaped macromolecules with the controlled number of branches and predetermined molecular weight characteristics of the arms are discussed. The hydrodynamic properties of the star-shaped fullerene-containing polymers are considered. The data on the small-angle neutron scattering study of self-organization of the stars in solutions are presented.

Proton-transfer anionic polymerization of vinyl monomers

Kinetic features and the mechanism of proton-transfer anionic polymerization of vinyl monomers (2-hydroxyethylacrylate (HEA) and l-hydroxyethylmethacrylate (HEMA) bearing groups with mobile hydrogen atom are discussed. It is established that polymerization combines features of chain growth and step growth polymerization. The living chain polymerization mechanism dominates at heterogeneous proceeding of the reaction. The peculiarities of the HEA and HEMA polymerization mechanism under the action of alkaline metals and their alcoholates are established. Polymerization initiated by tert-BuOLi is accompanied by a transesterification reaction with formation, along with macromonomer as main target product, of polyester di(met)acrylates, polyester diols and macrocycles. In addition to the transesterification reaction at HEMA polymerization initiated by potassium, formation of carbon chain fragments caused by interaction of enolate anion with double bond is revealed.

Single‐electron and two‐electron transfer in the anionic polymerization of vinyl monomers and the ring‐opening polymerization of lactones*

AbstractSingle‐electron‐transfer (SET) and two‐electron‐transfer reactions and their mechanisms were examined in the anionic polymerization of vinyl monomers and in the ring‐opening polymerization of lactones. SET resulted in the formation of radical anions or enolates at the initiation step of styrene or lactone polymerization with naphthalene sodium as a catalyst. However, alkali‐metal supramolecular complexes such as M+crown–M− (M = Na or K) were able to transfer two electrons to both these monomers to form carbanions as reactive intermediates. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2158–2165, 2002

Anionic block copolymerization of vinyl functionalized triphenylphosphines with styrene

The anionic polymerization of vinyl monomers with electron donating substituents was investigated. The 4- and 3-styryldiphenylphosphines were synthesized and homopolymerized at –85°C in tetrahydrofuran using sec-butyllithium as initiator. Block copolymerization studies were carried out using styrene as a comonomer. 4-Styryldiphenylphosphine (I) forms a much more stabilized anionic chain end than styrene (III). Thus only the sequence III/I is effective in block copolymerization. In contrast, 3-styryldiphenylphosphine (II) can be combined in both ways to block copolymers.

Anionic block copolymerization of vinyl functionalized triphenylphosphines with styrene

The anionic polymerization of vinyl monomers with electron donating substituents was investigated. The 4- and 3-styryldiphenylphosphines were synthesized and homopolymerized at –85°C in tetrahydrofuran using sec-butyllithium as initiator. Block copolymerization studies were carried out using styrene as a comonomer. 4-Styryldiphenylphosphine (I) forms a much more stabilized anionic chain end than styrene (III). Thus only the sequence III/I is effective in block copolymerization. In contrast, 3-styryldiphenylphosphine (II) can be combined in both ways to block copolymers.

Palm-tree and dumbbell like polystyrene structures based on C 60

By reacting anionic polymers such as polystyryllithium with C 60, “living” hexa-adducts have been prepared and used to initiate the anionic polymerization of vinyl monomers. If styrene is used as the monomer, only one chain is growing out from the fullerene core producing a “palm-tree” type structure. The outgrowing chain bearing on its end a carbanion, could be reacted with the coupling agent dibromoparaxylene to form “dumbbell” like macromolecules where two 6 branched PS stars are connected together by a PS chain of controlled length.

Addition of “Living” Polymers onto C60.

Abstract Various “living” polymers were grafted onto C60 The number of arms of the so obtained “star” molecules can be controlled by stoechiometry and/or by varying the reactivity of the carbanion on the “living” chain against a double bond on the C60. Even the oxanion of “living” polyethylenoxide is able to add onto the reactive double bonds on C60. In some conditions, the carbanions present on these alkaline salts of grafted fullerenes becomes able to initiate anionic polymerization of vinyl monomers. Using “living” poly(phenylvinylsulfoxide) as a precursor polymer for PA, polyacetylene chains could be attached to the fullerene.

Trimethylsilylmethyllithium: A novel initiator for the anionic polymerization of cyclosiloxanes and vinyl monomers

AbstractTrimethylsilylmethyllithium has been successfully used for the ring opening polymerization of cyclosiloxanes, in toluene or in the bulk, with the [211] cryptand or DMSO as promoters. Initiation reaction has been followed by 1H, 13C, 29Si and 7Li NMR in the case of D3 and D4 polymerizations. Suitable conditions have been found in which monomodal distributions of molecular weights of polysiloxanes are observed even in the case of D4 and 1,3,5,7‐tetramethyl‐1,3,5,7‐tetravinylcyclotetrasiloxane homopolymerizations and copolymerizations. This organolithium compound can also initiate the anionic polymerization of vinyl monomers such as butadiene, styrene and MMA.

Stereochemistry of anionic vinyl polymerization

AbstractThe stereochemistry of anionic polymerization of vinyl monomers: CH2=C(R)C(Y)=X where X and Y are O, N or C and R = H or alkyl is discussed in terms of a: the geometry of the ‐CH2C‐(R)C(Y)=X intermediate existing as E‐ or Z‐isomers; b: the interactions of cation (Li, Na, etc.) with the anion and coordinating groups on the penultimate or antepenultimate asymmetric carbon. The E/Z ratio appears to be determined directly by the s‐trans/s‐cis approach of the monomer. The nature of the coordination of the counter ion is considerably more complicated and is discussed in detail.

Complex bases: 13. Salt complex bases as new initiators in anionic polymerization of vinyl monomers

Inorganic salts have been used as activating agents of alkali amides, which led to salt complex bases MNH 2-M′Z. Salt complex bases or solid salt complex bases constitute good initiators for solution and bulk anionic polymerization of vinyl monomers. The influence of the nature of the activating agent and of the solvent used has been examined. Finally the polymers thus formed appear to be living ones.

Complex bases: 10. New complex bases. Application to solution anionic polymerization of vinyl monomers

Numerous new complex bases, MNH 2-ROM (M = Li, Na, K) are described. It is shown that these bases are able to initiate the polymerization of vinyl monomers in solvents such as tetrahydrofuran or toluene. The characteristics of the polymer obtained depend on the nature of the activating agent ROM. Moreover, the living nature of the polymer is demonstrated.

Electronic structure and geometry of the active centres in anionic polymerization of vinyl monomers

The charge distributions in the ions (CH 3CHR) and in the molecules CH 3CHRLi (RNO 2, CN, COOCH 3, C 6H 5, CHCH 2, H, NH 2 or OCH 3), modelling the active centres of the two extreme types in anionic polymerization, were calculated by the CNDO/2 method. The geometry of these compounds was partly optimized. Both the geometry and the charge distribution in anions were found to exhibit no strong dependence on R. This suggests that in free ion polymerization, the equality r 1 r 2 = 1 holds. The active centres of the polarized bond type are fairly varied. Two reasons for their reactivity may exist: the polarity of their CLi bond and their geometry facilitating the insertion of a monomer. The electronic structure of the neutral molecules considered correlates with the low degree of association of the living chains.

Anionic Polymerization of Vinyl Monomers

Abstract Addition polymerizations involving soluble organometallic species have received intensive attention in recent years with special reference to the type of counterion and solvent. An anionic mechanism is proposed for those systems where there is good reason to assume that the metal is strongly electropositive relative to the carbon (or other) atom at the tip of the growing chain. Hence, the metal, e.g. lithium, becomes a cation either in the free state or coupled with the growing carbanion. Under the appropriate experimental conditions, spontaneous termination is avoidable in many of those systems when one of the metals of Group I is used as the counterion. The alkali metals sodium and potassium were revealed to be polymerization initiators of isoprene in the disclosures of Matthews and Strange in 1910 and Harries in 1911. The first unambiguous report of the use of lithium in reactions with diolefins appears to be that of Ziegler and coworkers in 1934. Their work consisted of an investigation of the reaction between the alkali metals (lithium, sodium) or alkyllithium species and butadiene, isoprene, 2,3-dimethylbutadiene, or piperylene.

Anionic Polymerization of Vinyl Monomers with Organometallic Compound—Phosphoramide Systems

The polymerization of vinyl monomers with organometallic compounds was carried out in the presence of monodentate or bidentate phosphoryl compounds with —N(CH3)2 substituents. The polymerization of styrene or α-methylstyrene (α-MeSt) with organomagnesium compounds was more facilitated in the presence of the bidentate donors than in the presence of the monodentate type. In the polymerization of acrylonitrile (AN) with diethylzinc or organoaluminium compounds, the bidentate phosphoramides were less effective donors than the monodentate ones. The latter polymerization was considered to be caused by the coordination of both the phosphoramides and AN with the organometallic compounds, and to be reduced by the undesirable coordination of the bidentate phosphoramides to the sites required for the coordination of AN. The equilibrium monomer concentration ([M]e) in the polymerization of α-MeSt was dependent on the solvents used for the polymerization; the values of [M]e was smaller in toluene than in tetrahydrofuran.

Etude theorique de la reactivite des ions libres intervenant dans la polymerisation anionique de quelques monomeres vinyliques

The reactivities have been calculated for free ions involved in anionic polymerization of vinyl monomers. The copolymerization constants k AB available in the literature are compared to the stabilization energies involved in the reaction of carbanions with the same monomer. The reactivities of carbanions of living poly (2-vinyl pyridine), poly styrene and poly (substituted styrenes) with respect to 1-1,diphenylethylene have been computed. The rate constants of homopolymerisation have been compared with the variation of π energy between the “monomer” and “carbanion” states of these monomers. The occurrence of side-reactions during the polymerization of vinyl-pyridine has been investigated using quantum chemistry methods.