Self-assembling behavior of amphiphilic dendron coils in the bulk crystalline and liquid crystalline states
Self-assembling behavior of amphiphilic dendron coils in the bulk crystalline and liquid crystalline states
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DOI：
10.1021/ja801163m
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发表时间：
2008-06-04
影响因子：
15
通讯作者：
Cho, Byoung-Ki
中科院分区：
文献类型：
--
作者：
Chung, Yeon-Wook;Lee, Jeong-Kyu;Cho, Byoung-Ki
我们制备了一系列两亲性树枝状分子线圈（1-3），含有脂肪族聚醚树枝状分子与十八烷基外围和聚（环氧乙烷）（PEO）线圈（DP = 44）。在这项研究中的分子设计的重点是与一个固定的线性线圈，其中的热和自组装行为的树枝化分子线圈的变化（从第一到第三）进行了研究。所有树枝化分子线团都表现出两种结晶相，称为k（1）（结晶十八烷基链和PEO）和k（2）状态（结晶十八烷基链和熔融PEO）。十八烷基外围和PEO的结晶度随着代的增加而降低。特别地，含有第三代的树枝状卷曲（3）显示出PEO结晶度的急剧降低，这归因于最大的亲水树枝状核心片段的相当大的链折叠和增塑效应。所有的晶相均为双层片层结构。在从k（1）到k（2）的过程中，第一代树枝化线圈（1）中的周期性片层厚度减小，但有趣的是在3中增加。在十八烷基外围熔融后，1没有显示中间相（即，液晶相）。此外，树枝状分子线圈2（3）显示具有la 3d对称性的网络立方中间相（具有Pm 3 n的胶束立方），其在加热时转化为层状（六方柱状）中间相。值得注意的是，与传统的线性-线性嵌段共聚物相比，2和3中的温度依赖性介晶行为是完全相反的模式。在结晶和液晶相的不寻常的散装形态学现象，可以阐明由树枝状线圈架构和相关的线圈构象能。
We prepared a series of amphiphilic dendron coils (1-3) containing aliphatic polyether dendrons with octadecyl peripheries and a poly(ethylene oxide) (PEO) coil (DP = 44). The molecular design in this study is focused on the variation of dendron generation (from first to third) with a fixed linear coil, upon which the thermal and self-assembling behavior of the dendron coils was investigated in the bulk. All the dendron coils exhibit two crystalline phases designated as k(1) (both crystalline octadecyl chains and PEO) and k(2) states (crystalline octadecyl chains and molten PEO). Crystallinities for both octadecyl peripheries and the PEO decrease as generation increases. In particular, the dendron coil (3) containing third generation shows a drastic reduction of the PEO crystallinity, which is attributed to the considerable chain folding and plasticization effects by the largest hydrophilic dendritic core segment. All the crystalline phases are bilayered lamellar morphologies. On going from k(1), to k(2), the periodic lamellar thickness decreases in the dendron coil (1) with first generation, but interestingly increases in 3. After melting of octadecyl peripheries, 1 shows no mesophase (i.e., liquid crystalline phase). Additionally, dendron coil 2 (3) displays a network cubic mesophase with la3d symmetry (micellar cubic with Pm3n) which is transformed into a lamellar (hexagonal columnar) mesophase upon heating. Remarkably, the temperature-dependent mesomorphic behavior in 2 and 3 is a completely reverse pattern in comparison with conventional linear-linear block copolymers. The unusual bulk morphological phenomena in the crystalline and liquid crystalline phases can be elucidated by the dendron coil architecture and the associated coil conformational energy.