Lenoble Julie, Campidelli Stéphane, Maringa Natacha, Donnio Bertrand, Guillon Daniel, Yevlampieva Natalia, Deschenaux Robert
Institut de Chimie, Université de Neuchâtel, Avenue de Bellevaux 51, Case Postale 158, 2009 Neuchâtel, Switzerland.
J Am Chem Soc. 2007 Aug 15;129(32):9941-52. doi: 10.1021/ja071012o. Epub 2007 Jul 20.
Janus-type liquid-crystalline fullerodendrimers were synthesized via the 1,3-dipolar cycloaddtition of two mesomorphic dendrons and C60. By assembling poly(aryl ester) dendrons functionalized with cyanobiphenyl groups, displaying lamellar mesomorphism, with poly(benzyl ether) dendrons carrying alkyl chains, which display columnar mesomorphism, we could tailor by design the liquid-crystalline properties of the title compounds as a function of each dendron size. The liquid-crystalline properties were examined by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. Depending on the dendrimer generations, smectic (SmC and/or SmA phases) or columnar (Colr-c2mm or Colr-p2gg phases) mesomorphism was obtained. The supramolecular organization is governed by (1) the adequacy of the cross-sectional area of the dendrons, (2) the microsegregation of the dendrimer, (3) the deformation of the dendritic core, and (4) the dipolar interactions between the cyanobiphenyl groups. Comparison of the mesomorphic properties of two fullerodendrimers with those of model compounds (fullerene-free analogues) indicated that the C60 unit does not influence the type of mesophase that is formed. Molecular properties determined in solution (permanent dipole moment, specific dielectric polarization, molar Kerr constant) confirm that microsegregation persists in solution and strengthen the models proposed for the structure of the mesophases.
通过两个介晶树枝状分子与C60的1,3 - 偶极环加成反应合成了Janus型液晶富勒烯树枝状大分子。通过将带有氰基联苯基团且呈现层状介晶性的聚（芳基酯）树枝状分子与带有烷基链且呈现柱状介晶性的聚（苄基醚）树枝状分子组装在一起，我们可以根据每个树枝状分子的大小来设计调控标题化合物的液晶性质。通过偏光显微镜、差示扫描量热法和X射线衍射对液晶性质进行了研究。根据树枝状大分子的代数，可得到近晶相（SmC和/或SmA相）或柱状相（Colr - c2mm或Colr - p2gg相）的介晶性。超分子组织受以下因素控制：（1）树枝状分子横截面面积的适配性；（2）树枝状大分子的微相分离；（3）树枝状核心的变形；（4）氰基联苯基团之间的偶极相互作用。将两种富勒烯树枝状大分子的介晶性质与模型化合物（不含富勒烯的类似物）的介晶性质进行比较表明，C60单元不影响所形成的中间相类型。在溶液中测定的分子性质（永久偶极矩、比介电极化、摩尔克尔常数）证实了微相分离在溶液中持续存在，并强化了所提出的中间相结构模型。
