Gels with Well-Ordered Structures

Gels with Well-Ordered Structures

Colorful gel 多彩凝胶

Impressive colors of natural iridescence seen on insects and bird feathers are often the result of hierarchical structures. Peacock feathers are known to have barbules with irregular structures and a macroscopic pattern that enables diffused reflections of structural colors originating from periodic structures of melanin granules with submicron sizes. On the other hand, most artificial photonic crystals with tunable colors possess only regular structures that emit projections of diffraction spots or specular reflections, which are not the same as natural iridescence.
在昆虫和鸟类羽毛上看到的令人印象深刻的自然彩虹色的颜色往往是分层结构的结果。 已知孔雀羽毛具有不规则结构的圆柱和宏观图案，其能够产生源自具有亚微米尺寸的黑色素颗粒的周期性结构的结构颜色的漫反射。 另一方面，大多数具有可调颜色的人造光子晶体仅具有发射衍射斑或镜面反射投影的规则结构，这与自然彩虹色不同。

We are studying a hydrogel with tunable structural colors that originated from a superstructure consisting of submicron-scale multilayers, which form a macroscopic Tamagoyaki structure resembling a Japanese rolled-cake style multiple layer omelet. In this gel, polymerized bilayer membranes are periodically orientated in submicron spacing to form a multilayer in which layers of membrane and gel appear alternately. Such a structure shows reflection of iridescent colors essentially by multilayer interference, but in a distinctive pattern due to its Tamagoyaki structure.
我们正在研究一种具有可调结构颜色的水凝胶，其起源于由亚微米级多层组成的超结构，其形成类似于日本卷饼式多层煎蛋卷的宏观Tamagoyaki结构。在该凝胶中，聚合的双层膜以亚微米间隔周期性地定向以形成多层，其中膜和凝胶层交替出现。这种结构基本上通过多层干涉显示出彩虹色的反射，但由于其Tamagoyaki结构而呈现出独特的图案。

PBDT gel

Most soft bio-tissues possess well-ordered structures and are in a soft and wet gel-like state. However, synthesized gels are generally amorphous. To produce structured polymeric hydrogels, liquid crystals (LC) are introduced as dopants because of the possibility of forming self-assembled structures during the polymerization. As LCs, we used poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT), a water-soluble semi-rigid polyanion with a very high molecular weight and a very low critical nematic concentration.
大多数软质生物组织具有良好有序的结构，并且处于柔软和湿润的凝胶状态。 然而，合成的凝胶通常是无定形的。 为了制备结构化聚合物水凝胶，引入液晶（LC）作为掺杂剂，因为在聚合过程中可能形成自组装结构。 作为LC，我们使用聚（2,2'-二磺酰基-4,4'-联苯胺对苯二甲酰胺）（PBDT），一种水溶性半刚性聚阴离子，具有非常高的分子量和非常低的临界向列浓度。

A dual network gel, consisting of micrometer-scale network-like structures of semi-rigid polyion complexes nested in nanometer-scale polycationic networks, has been developed by polymerization of a cationic monomer in the presence of a small amount of PBDT as a dopant. Polymerization produces polycations that interact with oppositely charged semi-rigid PBDT to form complexes through electrostatic interactions. Self-assembly and viscoelastic phase separation of the polyion complexes compete with each other during the polymerization and render the micrometer-scale network-like structure, which is permanently frozen by the subsequent gelation (see Figure).
通过在少量PBDT作为掺杂剂存在下聚合阳离子单体，开发了一种双网络凝胶，其由嵌套在纳米级聚阳离子网络中的半刚性聚离子复合物的微米级网状结构组成。 聚合产生聚阳离子，其与带相反电荷的半刚性PBDT相互作用以通过静电相互作用形成复合物。 聚合物络合物的自组装和粘弹性相分离在聚合过程中彼此竞争，并形成微米级网络状结构，其通过随后的凝胶化而永久冷冻（参见图）。

Additionally, we succeeded in synthesizing hydrogels with uniaxially oriented structures by controlling the diffusional direction of multivalent ions that act as a physical cross-linker in PBDT solutions. Furthermore, using the DN technique, we synthesized highly ordered DN gels possessing excellent mechanical properties, particularly high extensibility, which exceeded 2200% of its original length under uniaxial elongation (see Figure, the left is the microstructure observed by SEM, the right is the elongation test of the gel).
此外，我们通过控制多价离子的扩散方向，成功地合成了具有单轴取向结构的水凝胶，多价离子在PBDT溶液中充当物理交联剂。 此外，使用DN技术，我们合成了具有优异机械性能，特别是高延展性的高度有序的DN凝胶，其在单轴伸长率下超过其原始长度的2200％（参见图，左边是通过SEM观察到的微观结构，右边是 凝胶的伸长试验）。