Hierarchical Organization of Single Crystal Polymorphs of Azobenzene Chromophore in Anisotropic Media Subjected to Local Thermal Gradients upon Cold Spraying
Hierarchical Organization of Single Crystal Polymorphs of Azobenzene Chromophore in Anisotropic Media Subjected to Local Thermal Gradients upon Cold Spraying
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冷喷涂局部热梯度各向异性介质中偶氮苯发色团单晶多晶型的分级组织
DOI：
10.1002/marc.202200044
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发表时间：
2022
影响因子：
4.6
通讯作者：
Youngs, Wiley
中科院分区：
文献类型：
--
作者：
Sutter, Thomas M.;Riley, Grant V.;Quasney, Kaitlin E.;Kyu, Thein;Golovaty, Dmitry;Wright, Bryan;Youngs, Wiley
本论文需要出现不同的晶体多晶型物的热淬火到不同的共存区域的二元偶氮苯生色团（ACh）/二丙烯酸酯（DA）的解决方案和偶氮苯/液晶（E7）的混合物。包括菱形和六边形形状的各种晶体拓扑结构的发展，可以见证的方式依赖于ACh/DA系统的晶体+液体共存区域的热淬火深度。在用压缩二氧化碳（CO2）流体喷射时，产生局部温度梯度，导致球晶形态，其显示在一些区域中局部经历扭曲的离散层状结构和在另一个区域中的分支树突或海藻。当使用压缩CO2流体喷射ACh/E7共混物时，可以在较亮的区域（非交叉偏振）偏振光学显微镜（POM）中辨别出从球晶核辐射的各种离散的多面单晶（包括针状、矩形、菱形和截短的六边形晶体）的分级组织，并且在较暗的交叉偏振区域中辨别出双向错。特别感兴趣的是，在ACh/E7中观察到的多面单晶多晶型物可以与在ACh/DA系统中观察到的层状扭曲和支化形成对比，并讨论了聚合物球晶生长的合理机制。
The present article entails the emergence of diverse crystal polymorphs following thermal quenching into various coexistence regions of binary azobenzene chromophore (ACh)/diacrylate (DA) solution and of azobenzene/nematic liquid crystal (E7) mixture. Development of various crystal topologies encompassing rhomboidal and hexagonal shapes can be witnessed in a manner dependent on thermal quenched depths into the crystal + liquid coexistence region of ACh/DA system. Upon spraying with compressed carbon dioxide (CO2) fluid, the local temperature gradient is generated resulting in spherulitic morphology showing discrete lamellae undergoing twisting locally in some regions and branched dendrites or seaweeds in another. When ACh/E7 blend is sprayed using compressed CO2fluid, hierarchical organization of various discrete faceted single crystals including needle, rectangular, rhombus, and truncated hexagonal crystals radiating from the spherulite core can be discerned in a brighter region (off cross‐polarization) polarized optical microscopy (POM) and nematic disclination in a darker cross‐polarized region. Of particular interest is that the observed faceted single‐crystal polymorphs in ACh/E7 may be contrasted to the lamellar twisting and branching observed in the ACh/DA system and plausible mechanisms of polymer spherulitic growth are discussed.