Asymmetric Star-branched Polymers Research Articles

Synthesis of multicomponent asymmetric star-branched polymers by iterative methodology with new diblock copolymer in-chain anions as building blocks

New AB diblock copolymer in-chain anions having poly(2-vinylpyridine) (P2VP) and/or poly(methyl methacrylate) (PMMA) blocks, whose anion is located at the junction between the A and B blocks, have been prepared by the 1:1 addition reaction of the living polymer (A) with the ω- or α-terminal 1-phenyl-1-(2-pyridinyl)ethylene-functionalized polymer (B). The P2VP-block-PS, PS-block-P2VP, P2VP-block-poly(4-tert-butyldimethylsilyloxystyrene), PS-block-PMMA, and P2VP-block-PMMA in-chain anions could be practically prepared for the first time. Based on this preparation, a newly synthesized 1,4-bis(1-(2-pyridinyl)ethenyl)benzene satisfactorily works as a key core agent, with which the polymers (A) can be connected to the polymer (B), and the in-chain anion can be generated between the A and B polymers. By developing the iterative methodology with such new block copolymer in-chain anions as the building blocks, the successive synthesis of the 3-arm ABC and 5-arm ABCDE μ-star polymers having PMMA and P2VP arms, which were synthetically difficult by the previous systems, have been successfully achieved. The success of the developed methodology demonstrates the further possibility to synthesize more component μ-star polymers.

Precise Synthesis of Novel Ferrocene-Based Star-Branched Polymers by Using Specially Designed 1,1-Diphenylethylene Derivatives in Conjunction with Living Anionic Polymerization

The precise synthesis of novel ferrocene-based regular and asymmetric star-branched polymers by a methodology using specially designed 1,1-diphenylethylene derivatives in conjunction with living anionic polymerization of ferrocenylmethyl methacrylate (FMMA) is described. The methodology involves three reaction steps, i.e., (1) introduction of 3-(tert-butyldimethylsilyloxymethyl)phenyl (SMOP) group(s) at the polymer chain end or in-chain, (2) conversion of the SMOP group(s) to α-phenyl acrylate function(s), and (3) a linking reaction of the α-phenyl acrylate function(s) with the living anionic polymer of FMMA or methyl methacrylate. By developing this methodology, a variety of 3-arm $$ {\text{AA}^{\prime}_{2}} $$ , A2B, AB2, ABC and 4-arm A4, A3B, A2B2, A2BC, and ABC2 star-branched polymers with well-defined structures have been successfully synthesized. The A, B, and C segments are poly(FMMA), polystyrene, and poly(methyl methacrylate), respectively.

Successive Synthesis of Asymmetric Star-Branched Polymers Based on Iterative Methodology Using 1,1-Diphenylethylene Derivatives of Alternative Choice at Each Iteration

We have demonstrated an advanced iterative methodology using specially designed 1-[4-(3-bromopropyl)phenyl]-1-phenylethylene (1) or 3,5-bis{3-[4-(1-phenylethenyl)phenyl]propoxy}benzyl bromide (2) of alternative choice at each iteration for the successive synthesis of asymmetric star polymers. The methodology involves only two sets of the following reaction conditions for the entire iterative reaction sequence: (a) a linking reaction of a living anionic polymer with a DPE-chain-functionalized polymer and (b) an in-situ reaction of 1 or 2 with the anion generated by the linking reaction to reintroduce the DPE functionality. The number of DPE moieties remains unchanged when 1 is used, whereas it doubles when 2 is used. In practice, various arrays of asymmetric star polymers could be successfully synthesized by repeating the iterative reaction sequence, (a) and (b), five times. The structural variation of the stars covers 3-arm AB2, 5-arm AB2C2, 5-arm AB2C4, 7-arm AB2C2D2, 9-arm AB2C2D4, 11-arm AB2C4D4, 15-ar...

Synthesis of well-defined block copolymers and star-branched polymers by using terminal 1,3-butadiene functionalized polymers as reactive building blocks

Terminal 1,3-buadiene (Bd) functional polymers are stoichiometrically reacted with living anionic polymers in a monoaddition manner in THF at −78 °C, but neither polymerization nor oligomerization occurs under the conditions. By utilizing this reactive but non-polymerizable character of the Bd function toward living anionic polymers, a variety of block copolymers and regular and asymmetric star-branched polymers were successfully synthesized. In these syntheses, the terminal Bd functionalized polymers work effectively as reactive building blocks, namely polymeric efficient linking agents, to construct such architectural polymers. Since all the polymer segments used for the syntheses were derived from living anionic polymers and the linking reactions quantitatively proceeded, the architectural polymers herein synthesized were well-defined in structure and were precisely controlled in chain length. A new protocol based on iterative approach by repeating a two reaction sequence involving linking reaction and re-introduction of Bd group was proposed and developed to successively synthesize asymmetric star-branched polymers up to a 6-arm ABCDEF type. The terminal Bd functionalized polymers were readily and quantitatively converted to anhydride or diepoxide functionalized polymers by Diels–Alder or oxidation reactions. Because of their high reactive termini, the resulting polymers are also usable as reactive building blocks to synthesize the core-functionalized star-branched polymers with carboxylic acids or hydroxyl groups. The reactions between terminal anhydride and amine functionalized polymers were carried out in bulk at 180 °C to examine the synthetic possibility of star-branched polymers under such conditions.

Successive Synthesis of Well-Defined Star-Branched Polymers by Iterative Methodology Based on Living Anionic Polymerization

The subject of this review is to introduce a novel iterative methodology based on living anionic polymerization using specially designed 1,1-diphenylethylene (DPE) derivatives recently developed for the synthesis of well-defined many armed star-branched polymers with same or chemically different arm segments. The methodology basically involves only two sets of the following reaction conditions for the entire iterative synthetic sequence: (a) a linking reaction of a living anionic polymer with a DPE-chain-functionalized polymer, and (b) an in situ reaction of a DPE-functionalized agent with the anion generated by the linking reaction to reintroduce the DPE functionality usable for the next reaction. The number of arms to be linked by each stage of the iteration depends on the starting core and DPE-functionalized agents and can dramatically increase by the agent of choice. New functional asymmetric star-branched polymers involving conductive and rigid rod-like poly(acetylene) segment(s) have been synthesized by the methodology using the intermediate polymer anions produced by the linking reaction as macroinitiators to polymerize 4-methylphenyl vinyl sulfoxide, followed by thermal treatment of the resulting star-branched polymers.

Successive Synthesis of Well-Defined Asymmetric Star-Branched Polymers up to Seven-Arm, Seven-Component ABCDEFG Type by an Iterative Methodology Based on Living Anionic Polymerization

The successive synthesis of asymmetric star-branched polymers with chemically different arms by the iterative methodology in which a 1,3-butadiene (Bd) functionality is utilized as a reaction site at each stage of the iteration, is described. The methodology involves only two sets of the following reaction conditions for the entire iterative synthetic sequence: (a) linking reaction of a living anionic polymer with the Bd functionality preintroduced into polymer and (b) reintroduction of the Bd functionality by reacting 4-methylene-5-hexenyl bromide with the Bd-derived anion in situ generated by the linking reaction. By repeating the two reaction sequence five times, a series of two-arm AB diblock, three-arm ABC, four-arm ABCD, five-arm ABCDE, followed by six-arm ABCDEF star-branched polymers were successively synthesized. In these polymers, the A, B, C, D, E, and F segments correspond to polystyrene, poly(α-methylstyrene), poly(4-methylstyrene), poly(4-methoxystyrene), poly(4-trimethylsilylstyrene), and p...

アニオン重合の基礎から最近の進歩 ４．リビングアニオン重合による特殊形態高分子の精密合成

Recent advances in precise synthesis of macromolecules with specially designed architectures will be reviewed in this paper. Such designed macromolecules include graft copolymers, comb-like polymers, cyclic polymers, regular and asymmetric star-branched polymers, and a variety of hyperbranched polymers with complexed structures as well as block copolymers and chain-end-functionalized polymers synthesized by living (anionic) polymerization. Their architectures are well defined in branching, position, and shape and chain structures are precisely controlled in molecular weights and molecular weight distributions. Recently, new macromolecules with more complex branched architectures have been further synthesized along with rapid progress of living anionic polymerization and new development of living polymerization systems with different mechanisms. These are star-branched polymers with many arms and multi-components, highly dense comb-like polymers having one polymer segment in each unit, star-linear block polymers, comb-like graft and star polymers, dendritic hyperbranched polymers. A particular example is a seventhgeneration well-defined dendrimer-like star-branched polymer having a Mn of 2000000 and comprised of 508 polymer segments and 512 end-functionalities. They are characteristic and quite different from linear polymers in physical property and behavior in solution, melt, and solid state. Furthermore, their different segments are segregated and self-organized at molecular level to form novel nano-scale supra-structures and molecular assemblies.

アニオン重合の基礎から最近の進歩 ３．リビングアニオン重合によるエラストマーの分子設計

This paper will review various molecular designs and syntheses of synthetic elastomers by means of living anionic polymerization of 1, 3-diene monomers such as 1, 3-butadiene and isoprene. By appropriately choosing polymerization variables such as initiator, solvent, temperature, concentration, and additive, a wide variety of poly(1, 3-butadiene)s and poly(isoprene)s with precisely controlled chain-lengths as well as desired microstructures have been available. Furthermore, random copolymers of styrene-1, 3-butadiene rubber (SBR) and styrene-1, 3-butadiene-isoprene rubber (SBIR) and ABA triblock copolymers of polystyrene-block-poly-1, 3-butadiene-block-polystyrene (SBS) and polystyrene-block-polyisoprene-block-polystyrene (SIS) have been industrially produced at the present time. The latter block copolymers are well known as thermoplastic elastomers where each segments are phase-separated and self-organized at molecular level and the polystyrene segments self-organized work as physically cross-linked points. Well-defined chain-end-functionalized poly-1, 3-butadiene and polyisoprene with hydroxyl groups at both chain-ends (one hydroxyl group per each chain-end) are synthesized by living anionic polymerization and used as model network elastomers. It has been found that the introduction of polar functional groups such as amino and hydroxyl groups into synthetic elastomers can affect significantly on their physical properties. We have recently established a novel methodology based on living anionic polymerization using specially designed 1, 1-diphenylethylene derivatives, by which multi-functionalization is possible at polymer chain-ends and/or in-chains. We have also demonstrated several possibilities of new synthetic elastomers such as chain-end-multi-functionalized poly-1, 3-dienes, regular and asymmetric star-branched polymers comprised of poly-1, 3-diene segments, and star-branched block copolymers of styrene and 1, 3-diene monomer, all of which can be synthesized by the above-mentioned methodology.

Synthesis of Asymmetric Star-Branched Polymers Having Two Polyacetylene Arms by Means of Living Anionic Polymerization Using 1,1-Diphenylethylene Derivatives

Two series of new 3-arm AE2, 4-arm ABE2, 5-arm ABCE2, and 5-arm AD2E2, 6-arm ABD2E2, 7-arm ABCD2E2 asymmetric star-branched polymers have been synthesized using living anionic polymers and 3,5-bis(3-(4-(1-phenylethenyl)phenyl)propoxy)benzyl bromide. The A, B, C, D, and E arms were polystyrene (A), poly(α-methylstyrene) (B), poly(4-methoxystyrene) (C), poly(4-trimethylsilylstyrene) (D), and poly(4-methylphenylvinyl sulfoxide) (E) segments. The methodology involves an addition reaction of either sec-BuLi or poly(4-trimethylsilylstyryl)lithium with two 1,1-diphenylethylene (DPE)-chain-functionalized polymers and a subsequent living anionic polymerization of 4-methylphenylvinyl sulfoxide in situ initiated with the two 1,1-diphenylalkyl anions generated by the addition reaction. Three DPE-functionalized polymers herein used were chain-end-functionalized polystyrene, in-chain-functionalized AB diblock copolymer, and core-functionalized 3-arm ABC star-branched polymer with two DPE moieties at chain end, junction...

Successive Synthesis of Well-Defined Many Arm Star-Branched Polymers by an Iterative Methodology Using a Specially Designed 1,1-Diphenylethylene

The synthesis of well-defined regular and asymmetric star-branched polymers having as many as 63 arms, each of similar or different composition, is described. This synthesis has been achieved by developing a new, iterative methodology using a specially designed functionalized reagent, 3,5-bis(3-(4-(1-phenylethenyl)phenyl)propoxy)benzyl bromide (5). This reagent is capable of introducing two 1,1-diphenylethylene (DPE) functions via one reaction site. The methodology involves only two sets of reactions for entire iterative reaction sequence: (a) an addition reaction of living anionic polymer(s) to DPE-chain-functionalized polymer to link polymer chain(s) and (b) an in situ substitution reaction of 5 with 1,1-diphenylalkylanions newly generated after the addition reaction. Two DPE functions are introduced per one anion. With this methodology, well-defined 3-, 7-, 15-, and 31-arm followed by 63-arm regular star-branched polystyrenes as well as 3-arm AB2, 7-arm AB2C4, and 15-arm AB2C4D8, followed by 31-arm AB...

Synthesis of Block Copolymers and Asymmetric Star-Branched Polymers Comprised of Polyacetylene and Polystyrene Segments via Ionic Bond Formation

Novel ion-bonded AB diblock copolymers and three-arm AB2 asymmetric star-branched polymers comprised of polyacetylene (A) and polystyrene (B) segments have been synthesized by the stoichiometric reaction of tert-amine-chain-end-functionalized poly(phenyl vinyl sulfoxide)s with either chain-end- or in-chain-carboxylated polystyrenes to link the two polymer segments via ionic bond, followed by thermal treatment to convert their poly(phenyl vinyl sulfoxide)s to polyacetylene segments. Periodic lamellar morphologies were observed in the cast films of such polymers by TEM measurement. The isolation of the nano-size sheet consisting of polyacetylene lamellar layers was attempted.

Successive synthesis of well-defined star-branched polymers by an iterative approach based on living anionic polymerization

To successively synthesize star-branched polymers, we developed a new iterative methodology which involves only two sets of the reactions in each iterative process: (a) an addition reaction of DPE or DPE-functionalized polymer to a living anionic polymer, and (b) anin-situ reaction of 1-(4-(4-bromobutyl)phenyl) -1-phenylethylene with the generated 1,1-diphenylalkyl anion to introduce one DPE functionality. With this methodology, 3-, 4-, and 5-arm, regular star-branched polystyrenes, as well as 3-arm ABC, 4-arm ABCD, and a new 5-arm ABCDE, asymmetric star-branched polymers, were successively synthesized. The A, B, C, D, and E arm segments were poly(4-trimethylsilylstyrene), poly(4-methoxystyrene), poly(4-methylstyrene), polystyrene, and poly(4-tert-butyldimethylsilyloxystyrene), respectively. All of the resulting star-branched polymers were well-defined in architecture and precisely controlled in chain length, as confirmed by SEC,1H NMR, VPO, and SLS analyses. Furthermore, we extended the iterative methodology by the use of a new functionalized DPE derivative, 1-(3-chloromethylphenyl)-1-((3-(1-phenylethenyl)phenyl)ethylene, capable of introducing two DPE functionalitiesvia one DPE anion reaction site in the reaction (b). The number of arm segments of the star-branched polymer synthesized by the methodology could be dramatically increased to 2, 6, and up to 14 by repeating the iterative process.

アニオン重合の基礎から最近の進歩 ２．リビング重合

This paper reviews a general aspect of living polymerization. A living polymerization proceeds only in initiation step, followed by propagation step, but in the absence of the kinetic steps of termination and/or chain transfer. The propagating chain-end active center remains its activity after the completion of the polymerization. It is therefore possible to control the molecular weight by adjusting the feed ratio of monomer to initiator. The molecular weight distribution becomes narrow when the initiation is faster than the propagation in rate. The index value, Mw/Mn, reaches to near 1 according to the equation, Mw/Mn=1+1/DP (DP: Number average degree of polymerization). Using the living polymerization methodology, a variety of macromolecules with complex architectures is precisely synthesized. These polymers involve block and graft copolymers, chain-end-functionalized polymers, cyclic polymers, comb-like polymers, regular and asymmetric star-branched polymers, and various hyperbranched polymers with well-defined structures. Recently developed other mechanistic types of living polymerizations are also described including group transfer, cationic, radical, transition metal and rare earth metal-catalyzed, and ring-opening metathesis polymerizations.

Successive Synthesis of Well-Defined Star-Branched Polymers by a New Iterative Approach Involving Coupling and Transformation Reactions

Successive synthesis of well-defined star-branched polymers has been successfully achieved by a new iterative methodology based on living anionic polymerization. The methodology involves only two sets of reaction conditions for the entire iterative reaction sequence: (a) a coupling reaction of the benzyl bromide-functionalized polymer with poly(substituted styryl)lithium end-capped with 1-(3-tert-butyldimethylsilyloxymethylphenyl)-1-phenylethylene to link two polymer chains and introduce 3-tert-butyldimethylsilyoxymethylphenyl group(s) of benzyl bromide precursor(s) and (b) a transformation reaction of the introduced precursor(s) into benzyl bromide functionality (functionalities) by treatment with (CH3)3SiCl−LiBr. By repeating these two reactions, an array of asymmetric star-branched polymers were successively synthesized. They involved 3-arm ABC, 4-arm ABCD and A2B2, and 6-arm A2B2C2 stars whose A, B, C, and D segments are polystyrene, poly(α-methylstyrene), poly(4-methylstyrene), poly(methyl methacryla...

Synthesis of Well-Defined Star-Branched Polymers by Coupling Reaction of Star-Branched Polymer Anions Comprised of Three Polymer Segments with Chain-End-Functionalized Polystyrenes with a Definite Number of Benzyl Bromide Moieties

For the synthesis of well-defined regular and asymmetric star-branched polymers, we have developed a new methodology using specially designed star-branched polymer anions comprised of three polymer...

Synthesis of block co-polymers and star-branched polymers consisting of conducting polyacetylene segments via ionic interaction to form ionic bonds

Chain-end- and in-chain-functionalized poly(phenyl vinyl sulfoxide) with a definite number of dimethylamino groups have been synthesized by living anionic polymerization of phenyl vinyl sulfoxide with functionalized initiators prepared from either 1-(4-dimethylaminophenyl)-1-phenylethylene or 1,1-bis(4-dimethylaminophenyl)ethylene with carbanionic species such as sec-BuLi, cumylpotassium and potassium naphthalenide. By the stoichiometric reaction of the dimethylamine-chain-functionalized poly(phenyl vinyl sulfoxide) thus prepared with ω-carboxylated poly-styrene and subsequent thermal treatment of the reaction mixture, novel block co-polymer and asymmetric star-branched polymers consisting of conducting polyacetylene (PA) and polystyrene segments via ionic interaction to form ionic bonds have been synthesized. The lamellar morphologies with conducting PA layers were observed in the cast films of such block co-polymer and star-branched polymer.

Synthesis of Chain-End-Functionalized Poly(methyl methacrylate)s with a Definite Number of Benzyl Bromide Moieties and Their Application to Star-Branched Polymers

The synthesis of well-defined chain-end-functionalized poly(methyl methacrylate)s with a definite number of benzyl bromide moieties via an iterative divergent approach starting from the living anionic polymer of methyl methacrylate is described. Only two sets of reactions involving coupling and transformation reactions are needed for the entire iterative reaction sequence. By repeating the iterative reaction sequence, chain-end-functionalized poly(methyl methacrylate)s with 2, 4, 8, and 16 benzyl bromide moieties were synthesized successfully. The resulting benzyl bromide-functionalized poly(methyl methacrylate)s underwent coupling reaction with living anionic polymers of methyl methacrylate, tert-butyl methacrylate, styrene, and isoprene to quantitatively afford well-defined regular 3-, 5-, 9-, and 17-arm star-branched poly(methyl methacrylate)s and asymmetric star-branched polymers containing poly(methyl methacrylate) segments.

Synthesis of Branched Polymers by Means of Living Anionic Polymerization. 12. Anionic Synthesis of Well-Defined Star-Branched Polymers by Using Chain-End-Functionalized Polystyrenes with Dendritic Benzyl Bromide Moieties

A series of five well-defined chain-end-functionalized polystyrenes with 2, 4, 8, 16, and 32 benzyl bromide moieties that were dendritically distributed were synthesized by an iterative methodology using only two sets of the reactions in each iterative reaction sequence. By coupling of these benzyl bromide-functionalized polystyrenes with 1,1-diphenylethylene (DPE)-end-capped polystyryllithium or polyisoprenyllithium in THF at −40 °C, 3-, 5-, 9-, 17-, and 33-arm star-branched polystyrenes as well as AA‘8 and AB8 asymmetric star-branched polymers were quantitatively synthesized. Moreover, a new chain-end-functionalized polystyrene with 16 phenols could successfully be synthesized by a similar coupling reaction between chain-end-functionalized polystyrene with 8 benzyl bromide moieties and the functionalized 1,1-diphenylalkyl anion prepared from sec-BuLi and 1,1-bis(4-tert-butyldimethylsilyloxyphenyl)ethylene, followed by deprotection. The well-defined structures and branched architectures of the resulting ...

Synthesis of Branched Polymers by Means of Living Anionic Polymerization. 13. Synthesis of Well-Defined Star-Branched Polymers via an Iterative Approach Using Living Anionic Polymers

We have developed a new iterative methodology for the synthesis of both regular and asymmetric star-branched polymers. The methodology involves only two sets of reactions for the entire iterative synthetic sequence: a living linking reaction of either 1,1-bis[3‘-(1‘ ‘-phenylethenyl)phenyl]ethylene or 1,1-diphenylethylene (DPE) functionalized polymers with living anionic polymers and an in-situ reaction for introducing DPE moieties into the polymers. By repeating the two reactions in the iteration, a series of regular star-branched polystyrenes of A3, A6, A9, A12, and A15 types and asymmetric star-branched polymers of A3B3 and A3B3C3 types were successfully synthesized. There does not seem to be a steric limitation even in the fifth iteration. The A and B segments in these star-branched polymers were polystyrene and poly(4-methoxystyrene), respectively, and the C segment was poly(4-tert-butyldimethylsilyloxystyrene), poly(4-trimethylsilylstyrene), or polyisoprene. Their arm segments were precisely control...