Synthèse anionique de polystyrènes ramifiés en éatoile à quatre et six branches

Meunier, Par Jean‐Claude; Leemput, Robert Van

doi:10.1002/macp.1971.021420101

Cited by 43 publications

(17 citation statements)

References 68 publications

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“…[7][8][9][10] The functionalities of the prepolymers (TESiP-PS) thus obtained were determined by carrying out their condensation reactions in the presence of sodium hydroxide as catalyst. The results are shown in Table I.…”

Section: Synthesis Of Tesip-psmentioning

confidence: 99%

Synthesis and Condensation of 3-(Triethoxysilyl)propyl-Terminated Polystyrene

Suzuki

Oku

Takaki

et al. 2003

Polym J

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ABSTRACT:A well-defined polymeric silane coupling agent, 3-(triethoxysilyl)propyl-terminated polystyrene (TESiP-PS) was synthesized by reaction of polystyryllithium with (3-chloropropyl)triethoxysilane. The reaction is greatly affected by reaction conditions. The yield of TESiP-PS was quantitative in a benzene/tetrahydrofuran medium at 0• C, whereas it was as low as 5% in benzene at room temperature. TESiP-PS obtained under the former conditions has 95% functionality and a monodispersity of 1.05. Condensation of TESiP-PS proceeds quantitatively in the presence of either base or acid catalyst. This result is different from that for triethoxysilyl-terminated polystyrene (TESi-PS), which undergoes complete cleavage in the presence of base catalysts. This sharp difference indicates that the introduction of a trimethylene group between the trimethoxysilyl group and polystyrene effectively suppressed the cleavage reaction.

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Section: Synthesis Of Tesip-psmentioning

confidence: 99%

Synthesis and Condensation of 3-(Triethoxysilyl)propyl-Terminated Polystyrene

Suzuki

Oku

Takaki

et al. 2003

Polym J

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“…As a result, considerable amounts of star polymers with lower and higher arms than desired were formed. 105,106 Recently, Gauthier and Möller have reported that the side reactions can be virtually eliminated by end-capping polystyryllithium with DPE in the reaction of chloromethylated polystyrene with polystyryllithium. 107,108 More recently, Hirao et al 109 and Hadjichristidis et al 110 have demonstrated that both poly(chloromethylstyrene)s and poly(bromomethylstyrene)s also couple quantitatively with polystyryllithium and polyisoprenyllithium endcapped with DPE in THF at −40 • C or under the similar conditions.…”

Section: Coupling Reaction Of Living Anionic Polymers With Benzyl Halmentioning

confidence: 99%

Precise Synthesis of Regular and Asymmetric Star Polymers and Densely Branched Polymers with Starlike Structures by Means of Living Anionic Polymerization

Hirao

Hayashi

Tokuda

et al. 2002

Polym J

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ABSTRACT:The subject of this review is to present new synthetic methodologies recently developed by us, which are applicable to both regular and asymmetric star polymers with well-defined architectures. The first methodology involves the coupling reaction of a variety of living anionic polymers of styrene, α-methylstyrene, isoprene, tert-butyl methacrylate, and ethylene oxide with novel chain-end-and in-chain-functionalized polymers with a definite number of benzyl halide moieties intentionally designed as polymeric coupling agents. In the second methodology, we propose a new concept based on iterative approach, with which star polymers can be successively and, in principle, unlimitedly synthesized by repeating the iterative reaction sequence. Finally, a convenient synthesis of densely branched polymers with starlike structures is presented by the quantitative coupling reaction of living anionic polymers with reactive benzyl halide-functionalized backbone polymers based on a grafting-onto method.KEY WORDS Star Polymer / Asymmetric Star Polymer / Living Anionic Polymerization / Iterative Methodology / Polymeric Coupling Agent / 1,1-Diphenylethylene Derivative / Star polymers are branched polymers in which more than three linear polymer chains are linked together at one end of each chain by a central core or a single branch. They have physical properties in bulk, melt, and solution quite distinct from linear analogues. For this reason, star polymers have been widely studied from both synthetic and theoretical points of view. [1][2][3][4][5][6][7][8][9] It is of course essential to use star polymers with welldefined structures for evaluating fundamental understanding regarding the effect of chain branching on such physical properties.At the present time, the most successful methodologies for the synthesis well-defined regular star polymers have been developed mainly based on coupling reactions of living anionic polymers of styrene and 1,3-dinene monomers with multifunctional chlorosilane compounds as electrophilic coupling agents. A variety of star polymers with a definite number of three to eighteen arms have been synthesized. [10][11][12][13][14][15][16][17][18][19] Furthermore, the successful syntheses of the 32-, 64-, and even 128-arm star polymers by using specially designed carbosilane dendrimers have been reported so far. 20,21 Currently, great attention has been paid to more complex asymmetric star polymers whose arms differ in molecular weight and chemical composition, since star polymers of this type are expected to exhibit interesting and unique physical performance originated from their † To whom correspondence should be addressed.branched architectures as well as heterophase structures. [22][23][24][25][26][27][28][29][30][31][32][33] Synthesis of asymmetric star polymers is generally more difficult than that of regular star polymers. In the synthesis of regular star polymers, for example, their arms can be simultaneously introduced by one reaction. On the other hand, two or more highyielding reactions...

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“…15 This prediction, contradictory to the behavior of experimental A 2 for star polymers, at least, with f 4, prompted us to examine the end effects on A 2 of four-arm star PS as was done for linear PS. We note that the previously investigated star polystyrene samples, anionically synthesized with butyllithium, [16][17][18][19][20] had a butyl group at each arm end.In the present work, we prepared three and two low molar mass samples of four-arm star polystyrenes with a benzyl group (4SPS-Bz) and a butyl group (4SPS-Bu) at each arm end, respectively, and determined their A 2 and A 3 (the third virial coefficient) in cyclohexane at Â by light scattering. Our interest in A 3 was to see whether the third coefficients for the two star polymers increase with lowering M w as was found for linear polystyrenes by Mizuno et al…”

mentioning

confidence: 90%

mentioning

confidence: 90%

Effects of Chain Ends and Three-Segment Interactions on Second and Third Virial Coefficients of Four-Arm Star Polystyrenes

2009

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Second and third virial coefficients (A 2 and A 3 , respectively) for cyclohexane solutions (34.5 C) of three four-arm star polystyrene (PS) samples with a benzyl group at each arm end (4SPS-Bz) and two four-arm star PS samples with a sec-butyl group at each arm end (4SPS-Bu) were determined as functions of weight-average molecular weight M w lower than 1:5 Â 10 4 . As in the case for linear PS with benzyl ends, A 2 for 4SPS-Bz at the theta temperature (34.5 C), where A 2 vanishes for sufficiently high M w , was negative and decreased with lowering M w in contrast to the increase of positive A 2 for 4SPS-Bu. The negative A 2 for 4SPS-Bz was ascribed to the effects of three-segment interactions and binary interactions between middle and junction point segments, while the positive A 2 for 4SPS-Bu was explained as due to the effects from arm ends. These findings reveal that the previously observed lowering in apparent theta temperature (with decreasing M w ), where A 2 ¼ 0 for a given M w , for four-arm star polystyrene is attributed to the arm-end effect. The values of A 3 for both 4SPS-Bz and 4SPS-Bu were positive and increased with decreasing M w at the theta temperature, showing significant three-segment interactions among two middle and one junction point or one arm-end segment. 1 found from light scattering measurements that the second virial coefficient A 2 of linear polystyrene (PS) with benzyl ends (benzyl-PS) in cyclohexane at the theta point Â (34.5 C) becomes negative and decreases with decreasing weight-average molecular weight M w in contrast to positive and increasing A 2 for linear PS with a butyl group at one of the chain ends (butyl-PS), 2,3 where Â is defined as the temperature at which A 2 vanishes for sufficiently high molecular weight M. They explained the negative A 2 for benzyl-PS as due to the effects from three-segment interactions with negligibly small chain-end effects. On the other hand, for butyl-PS the end effects 4 on A 2 were predominant, demonstrating that the chain-end groups strongly affect A 2 of low M polystyrene (M w < 3 Â 10 4 ) at Â. It is well-known for star polymers that the apparent theta temperature Â app , where A 2 ¼ 0 for a given M, decreases with lowering M.5-11 This is equivalent to an increase in A 2 with decreasing M at a fixed temperature Â. Such molecular weight dependence of Â app (or opposite dependence of A 2 at Â) for star polymers has been interpreted as due to effects of threesegment interactions by theories based on the smootheddensity model. 12,13 However, a more rigorous perturbation calculation 14 predicts a decrease in A 2 at Â with deceasing M for f (the number of arms) less than five. 15 This prediction, contradictory to the behavior of experimental A 2 for star polymers, at least, with f 4, prompted us to examine the end effects on A 2 of four-arm star PS as was done for linear PS. We note that the previously investigated star polystyrene samples, anionically synthesized with butyllithium, [16][17][18][19][20] had a butyl group at each arm end.In t...

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Synthèse anionique de polystyrènes ramifiés en éatoile à quatre et six branches

Cited by 43 publications

References 68 publications

Synthesis and Condensation of 3-(Triethoxysilyl)propyl-Terminated Polystyrene

Synthesis and Condensation of 3-(Triethoxysilyl)propyl-Terminated Polystyrene

Precise Synthesis of Regular and Asymmetric Star Polymers and Densely Branched Polymers with Starlike Structures by Means of Living Anionic Polymerization

Effects of Chain Ends and Three-Segment Interactions on Second and Third Virial Coefficients of Four-Arm Star Polystyrenes

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