Precise synthesis of asymmetric star-shaped polymers by coupling reactions of new specially designed polymer anions with chain-end-functionalized polystyrenes with benzyl bromide moieties

Abstract

We have developed a novel methodology using polymer anions specially designed to comprise either of the three same or different polymer segments for the synthesis of well-defined regular and asymmetric star-shaped polymers. The polymer anion was prepared by the addition reaction of living anionic polymer to in-chain-functionalized polymer with 1,1-diphenylethylene (DPE) moiety and in situ coupled with chain-end-functionalized polystyrene with two or four benzyl bromide moieties. Although the anions located at the cores of 3-armed star polymers were believed to be highly sterically hindered, the coupling reactions proceeded virtually quantitatively under the conditions in THF at 2 78 8C for 24 h. Regular 7-armed A 7 and 13-armed A 13 star-shaped polystyrenes as well as quite new asymmetric 7-armed A 2 B 2 C 2 D and 13-armed A 4 B 4 C 4 D star-shaped polymers were synthesized in ca. 100% yields. Four polymer segments, A, B, C, and D, were, poly(4-trimethylsilylstyrene), poly(4-methoxystyrene), poly(4-methylstyrene), and polystyrene prepared by sec-BuLi-initiated living anionic polymerization. Thus, three same or different polymer chains could be simultaneously introduced into either two or four benzyl bromide reaction sites only by one-step coupling reaction with the above-prepared polymer anion. The resulting star-shaped polymers all were welldefined in architecture and precisely controlled in-chain length and composition. Accordingly, they have a high molecular weight and structural homogeneity. Among them, asymmetric star-shaped polymers synthesized herein are the first successful examples comprised of four plural different polymer segments. As expected, new morphologies with nanoscopic ordered structures applicable to nanotechnology have been expressed. q

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

“…[53][54][55][56] The synthetic procedure is illustrated in Scheme 1. 1-(4-(3-Bromopropyl)-phenyl)-1-phenylethylene (1) is used as a DPE-functionalized agent in this procedure to reintroduce the DPE functionality usable for the next synthesis.…”

“…Synthesis of DPE-chain-end-functionalized PMSiS (A), DPE-in-chain-functionalized AB diblock copolymer (AB), DPE-core-functionalized 3-arm ABC, 4-arm ABCD, and 5-arm ABCDE asymmetric star-branched polymers by iterative methodology using 1 polymer having chemically different five arms. 52,58,59 Since the E segment is readily and quantitatively converted to poly(4-vinylphenol) by treatment with (C 4 H 9 ) 4 NF under neutral conditions, 53 the 5-arm ABCDE star can be changed to a new functional star-branched polymer having poly(4-vinylphenol) segment. This segment is acidic and hydrophilic and becomes water-soluble in basic media.…”

Synthesis of 4-arm methyl methacrylate star polymer by atom transfer radical polymerization

“…Currently, star polymers have attracted considerable attention because of their unique structure and properties [6,7]. Design and synthesis of star polymers and the study on their structure-property relationship have become the forefront in macromolecular science [8][9][10][11]. Methods toward making star polymers fall into two routes, the core-first method [12,13] and the so-called arm-first method [14].…”

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

“…The introduction of arms different in composition into star-branched polymers is also limited. For example, several 3-arm three-component ABC and the related asymmetric stars are now available, − ,− but only four synthetic examples of 4-arm four-composition ABCD stars have been reported. − Very recently, we have successfully synthesized more complex 7-arm A 2 B 2 C 2 D, 13-arm A 4 B 4 C 4 D,and 5-arm ABCDE asymmetric star-branched polymers for the first time. , The synthetic limitation is attributed to the facts that three or more quantitative nature of reactions for the introducing of different arms and isolation of the intermediate products are often required during the synthesis.…”

“…HAr), 6.39 (s, 1H, HAr), 5.45 (s, 2H, CH2 ) C-Ar), 5 42. (s, 2H, CH 2 dC-Ar), 4.40 (2, 2H, Ar-CH 2 -Br), 3.97 (t, 4H, Ar-O-CH 2 -), 2.82 (t, 4H, Ar-CH 2 -CH 2 -), 2.11 (pentad, 4H, -CH 2 -2 : C, 76.51; H, 6.11; Br, 12.41.…”