Poppe Silvio, Poppe Marco, Ebert Helgard, Prehm Marko, Chen Changlong, Liu Feng, Werner Stefan, Bacia Kirsten, Tschierske Carsten
Department of Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes Str. 2, 06120 Halle, Germany.
State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China.
Polymers (Basel). 2017 Sep 26;9(10):471. doi: 10.3390/polym9100471.
Polyphilic self-assembly leads to compartmentalization of space and development of complex structures in soft matter on different length scales, reaching from the morphologies of block copolymers to the liquid crystalline (LC) phases of small molecules. Whereas block copolymers are known to form membranes and interact with phospholipid bilayers, liquid crystals have been less investigated in this respect. Here, series of bolapolyphilic X-shaped molecules were synthesized and investigated with respect to the effect of molecular structural parameters on the formation of LC phases (part 1), and on domain formation in phospholipid bilayer membranes (part 2). The investigated bolapolyphiles are based on a rod-like π-conjugated oligo(phenylene ethynylene) (OPE) core with two glycerol groups being either directly attached or separated by additional ethylene oxide (EO) units to both ends. The X-shape is provided by two lateral alkyl chains attached at opposite sides of the OPE core, being either linear, branched, or semiperfluorinated. In this report, the focus is on the transition from polyphilic (triphilic or tetraphilic) to binary amphiphilic self-assembly. Polyphilic self-assembly, i.e., segregation of all three or four incorporated units into separate nano-compartments, leads to the formation of hexagonal columnar LC phases, representing triangular honeycombs. A continuous transition from the well-defined triangular honeycomb structures to simple hexagonal columnar phases, dominated by the arrangement of polar columns on a hexagonal lattice in a mixed continuum formed by the lipophilic chains and the OPE rods, i.e., to amphiphilic self-assembly, was observed by reducing the length and volume of the lateral alkyl chains. A similar transition was found upon increasing the length of the EO units involved in the polar groups. If the lateral alkyl chains are enlarged or replaced by semiperfluorinated chains, then the segregation of lateral chains and rod-like cores is retained, even for enlarged polar groups, i.e., the transition from polyphilic to amphiphilic self-assembly is suppressed.
多亲性自组装导致空间分隔，并在不同长度尺度的软物质中形成复杂结构，其范围从嵌段共聚物的形态到小分子的液晶（LC）相。虽然已知嵌段共聚物可形成膜并与磷脂双层相互作用，但液晶在这方面的研究较少。在此，合成了一系列bola多亲性X形分子，并研究了分子结构参数对LC相形成（第1部分）以及磷脂双层膜中畴形成（第2部分）的影响。所研究的bola双亲分子基于棒状π共轭低聚（亚苯基乙炔）（OPE）核，两个甘油基团直接连接或通过额外的环氧乙烷（EO）单元连接到两端。X形由连接在OPE核相对两侧的两条侧链提供，这些侧链可以是线性、支化或半全氟化的。在本报告中，重点是从多亲性（三亲性或四亲性）到二元两亲性自组装的转变。多亲性自组装，即将所有三个或四个并入的单元分离到单独的纳米隔室中，导致形成六方柱状LC相，呈现出三角形蜂窝状。通过缩短侧链烷基的长度和体积，观察到从明确的三角形蜂窝状结构到简单六方柱状相的连续转变，这种转变以亲脂性链和OPE棒形成的混合连续体中六方晶格上极性柱的排列为主导，即向两亲性自组装的转变。在增加极性基团中EO单元的长度时也发现了类似的转变。如果侧链烷基增大或被半全氟化链取代，那么即使极性基团增大，侧链和棒状核的分离也会保留，即从多亲性到两亲性自组装的转变受到抑制。
