Synthesis and Visualization of a Core Cross-Linked Star Polymer Carrying Optically Active Rigid-Rod Helical Polyisocyanide Arms and Its Chiral Recognition Ability
Synthesis and Visualization of a Core Cross-Linked Star Polymer Carrying Optically Active Rigid-Rod Helical Polyisocyanide Arms and Its Chiral Recognition Ability
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DOI：
10.1021/ma201998z
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发表时间：
2011-11-08
期刊：
影响因子：
5.5
通讯作者：
Yashima, Eiji
中科院分区：
文献类型：
--
作者：
Miyabe, Toshitaka;Iida, Hiroki;Yashima, Eiji
星星型聚合物是一类支化聚合物，由于其活性聚合技术的优势、三维核壳结构的多样性以及不同于线性聚合物的独特性能和功能，在过去的几十年里引起了人们的极大关注。1单体的活性离子和自由基聚合，然后与双官能共聚单体交联（“臂优先”方法）2经常被用于设计和合成由密集交联的核和线性辐射的多个臂组成的星星聚合物，这使得我们能够生产具有特定功能的星星聚合物，1b例如催化活性3和分子识别能力，4通过在核或臂段引入所需的官能团。尽管已经制备了具有不同数目的臂、化学组成和官能团的各种星星聚合物，但是迄今为止制备的大多数星星聚合物是光学惰性的。1光学活性的星星聚合物，特别是那些带有棒状单手螺旋臂的聚合物，4 b，5是相当罕见的，尽管它们在实际应用中作为对映选择性催化和吸附剂的新型手性材料的潜力6，因为它们独特的螺旋束结构是由自组装螺旋臂产生的，其可以为对映异构体和手性聚合物的有效手性识别提供受限的手性环境。为此，我们已经基于“臂优先”方法合成了一种带有棒状螺旋聚异氰化物臂的新型光学活性星星聚合物（M-poly-L-1（R）-B-3）（图1）。我们的设计方法建立在我们以前的发现基础上，即具有不同分子量（MW）和窄分子量分布（MWD）的右（P）和左（M）螺旋聚异腈。（P-和M-聚-L-1，分别）可以通过使用μ-聚乙烯醇（μ-C1-C2-乙炔二基铂钯催化剂（2），7，然后用丙酮进行简单的分馏（图1）。8，9通过高分辨率原子力显微镜（AFM）8显示的分级的单手螺旋聚异腈（P-和M-聚-L-1 s）10保持了它们的活性特征，并且可以用作异腈的进一步嵌段共聚的引发剂（大分子引发剂）。11.聚异氰化物具有220 nm的前所未有的长余辉长度，通过分子内氢键网络稳定，
Star polymers, a class of branched polymers, have attracted great attention over the past few decades because of their greater accessibility by well-established living polymerization techniques, structural diversity in three-dimensional (3D) coreÀshell architectures, and unique properties and functions being different from those of the corresponding linear counterparts. 1 Living ionic and radical polymerizations of monomers followed by cross-linking with a difunctional comonomer (“arm-first” approach) 2 have frequently been employed for the design and synthesis of star polymers consisting of a densely cross-linked core and linear radiating multiple arms, which enables us to produce star polymers bearing specific functions, 1b such as a catalytic activity3 and molecular recognition ability, 4 by introducing the desired functional groups at the core or the arm segments. Although a variety of star polymers with a varying number of arms, chemical compositions, and functional groups have been prepared, most of the star polymers prepared to date are optically inactive. 1 Optically active star polymers, in particular those carrying rodlike one-handed helical arms, 4b, 5 are quite rare in spite of their potential in practical applications as novel chiral materials for enantioselective catalysis and adsorbents6 because of their unique helix-bundle structures generated by selfassembled helical arms, which may provide confined chiral environments for the efficient chiral recognition of enantiomers and chiral polymers.To this end, we have synthesized a novel optically active star polymer (M-poly-L-1 (À)-b-3) bearing rodlike helical polyisocyanide arms based on the “arm-first” approach (Figure 1). Our design approach builds upon our previous findings that both right (P)-and left (M)-handed helical polyisocyanides with a different molecular weight (MW) and a narrow molecular weight distribution (MWD)(P-and M-poly-L-1s, respectively) can be obtained by the living polymerization of an enantiomerically pure phenyl isocyanide bearing an L-alanine pendant with a long n-decyl chain (L-1) using the μ-ethynediyl PtÀPd catalyst (2), 7 followed by the facile fractionation with acetone (Figure 1). 8, 9 The fractionated single-handed helical polyisocyanides (P-and M-poly-L-1s) 10 as revealed by high-resolution atomic force microscopy (AFM) 8 maintained their living feature and can be used as an initiator (macroinitiator) for the further block copolymerizations of isocyanides. 11 The polyisocyanides possess an unprecedented long persistence length of 220 nm stabilized by intramolecular hydrogen-bonding networks through