Synthesis Of Well-Defined Star-Branched Polymers Research Articles

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 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.

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 Well-Defined Star-Branched Polymers by Using Chain-End-Functionalized Polystyrenes with a Definite Number of 1,3-Butadienyl Groups and Its Derivatized Functions

A series of new chain-end-functionalized polystyrenes with two, four, and eight 1,3-butadienyl groups (PS(Bd) n, n = 2, 4, and 8) were synthesized by the reaction ofchain-end-functionalized polystyrenes with the same numbers of benzyl bromide moieties with the 1,1-diphenylalkyl anion prepared from oligo(α-methylstyryl)lithium and 1-[4-(4-methylene-5-hexenyl)phenyl]-1-phenylethylene. These 1,3-butadiene-functionalized polymers reacted efficiently with polystyryllithium (PSLi) to afford well-defined 3-, 5-, and 9-arm star-branched polystyrenes. A successive synthesis from (PS(Bd) 4 to 5-arm followed by 9-arm star-branched polystyrenes was demonstrated by twice repeating the reaction sequence involving the reaction of PSLi with (PS(Bd) 4 and subsequent in-situ introduction of 1,3-butadienyl groups via the generated anions. The terminal 1,3-butadienyl groups were quantitatively converted into highly reactive anhydride and epoxy functions by the Diels-Alder and epoxidation reactions, respectively. The resulting anhydride- and epoxy-functionalized polymers were successfully used as new polymeric coupling agents to synthesize well-defined star-branched polystyrenes.

Synthesis of Well-Defined Star-Branched Polymers by Coupling Reactions of Polymer Anions Consisting of Two Polymer Chains with Chain-End-Multifunctionalized Polystyrenes with Benzyl Bromide Moieties

To synthesize star-branched polymers, we have developed a new methodology of using polymer anions (Mw = ca. 10 kg/mol) consisting of the same or different two polymer chains in the coupling reaction of chain-end-multifunctionalized polystyrenes with 4, 8, and 16 benzyl bromide moieties. The coupling reactions efficiently proceeded to afford 9-, 17-, and 33-arm regular star-branched polystyrenes as well as A5B4, A9B8, and A17B16 asymmetric stars consisting of polystyrene (A) and poly(4-trimethylsilylstyrene) (B) segments in greater than 85% isolated yields. However, the yields of the coupling reactions were high but not quantitative when either chain-end-functionalized polystyrene with 32 benzyl bromide moieties or a high molecular weight polymer anion (Mw = 20.0 kg/mol) was used.

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...

Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 8. Synthesis of Well-Defined Star-Branched Polymers by an Iterative Approach Based on Living Anionic Polymerization Using 1,1-Diphenylethylene Derivatives

The synthesis of well-defined four- and six-arm star branched polymers in which arms differ either in molecular weight or composition has been achieved via a new iterative approach based on living anionic polymerization using 1,1-diphenylethylene (DPE) derivatives. Each stage in the iteration involves two reactions: a living functionalization reaction of living anionic polymer with DPE derivatives and an in-situ reaction of the resulting linked product having two anions with 1-4-(4-bromobutyl)phenyl]-1-phenylethylene to introduce two DPE moieties into the polymer. In each living functionalization reaction, a 1.2-fold excess or more of living anionic polymer relative to DPE moiety was employed to complete the reaction. Asymmetric A2A′2 and A2A′2A′′2 star-branched polystyrenes as well as A2B2 and A2B2C2 heteroarm star-branched polymers were synthesized by repeating the iteration synthetic sequence two and three times, respectively. Since the polymers obtained by each reaction stage were contaminated with their precursor polymers, they were isolated by SEC fractionation. Their high degrees of compositional, molecular weight and architectural homogeneity were confirmed by the analytical results of SEC, SLS, VPO, 1H NMR and viscosity measurements.