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Nematic Phase of Plate-like Semicrystalline Block Copolymer Single Crystals in Solution Studied by Small-Angle X-Ray Scattering
Langmuir ( IF 3.7 ) Pub Date : 2021-02-09 , DOI: 10.1021/acs.langmuir.0c03370 Enyi Chi 1 , Haiying Huang 1, 2 , Fajun Zhang 3 , Tianbai He 1, 2
Langmuir ( IF 3.7 ) Pub Date : 2021-02-09 , DOI: 10.1021/acs.langmuir.0c03370 Enyi Chi 1 , Haiying Huang 1, 2 , Fajun Zhang 3 , Tianbai He 1, 2
Affiliation
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Crystalline block copolymers have been used to prepare plate-like colloidal systems with well-controlled size, shape, and size distribution. The isotropic-to-nematic (I–N) phase transition of the novel plate-like colloidal particle suspensions has been reported previously. In this work, we focus on the characterization of the solution structure of the crystals and the N-phase using small- and ultrasmall-angle X-ray scattering techniques (SAXS/USAXS). The system has polystyrene-block-poly(l-lactide) (PS-b-PLLA) block copolymer single crystals (BCSCs) with different sizes dispersed in p-xylene. These crystals are truncated lozenge in shape and have effective diameters ranging from 550 to 4000 nm with a uniform dry thickness of 18.0 nm. Scattering of the individual crystal in solution can be simplified using a disc model with a core layer of 9–10 nm due to the lower contrast of the tethered PS layer. BCSC suspensions filled in thin quartz capillaries are prepared for monitoring the structural information. SAXS measurements of the isotropic phase show a strong face-to-face correlation, indicating that platelets form small stacked clusters in solutions. The isotropic phase is thus a coexistence of single crystals and the stacked multiple-layered clusters. The face-to-face spacing, d, in the N phases is around 75–90 nm, which increases slightly upon increasing the size of crystals. For a given system, the spacing does not change with increasing concentration under the current experimental conditions. Finally, the possible formation of lamellar domains within the N phase is also discussed due to the lateral attraction of this system. These results demonstrate the importance of the lateral attraction between the polar crystalline PLLA blocks on the formation of the N phase: the BCSCs self-assemble into larger sheets via the lateral attraction, which further enhances the I–N transition.
中文翻译：
小角度X射线散射研究板状半结晶嵌段共聚物单晶的向列相
结晶嵌段共聚物已用于制备具有良好控制的尺寸，形状和尺寸分布的板状胶体体系。新型板状胶体颗粒悬浮液的各向同性向向列相（I–N）相变已有报道。在这项工作中，我们专注于使用小和超小角度X射线散射技术（SAXS / USAXS）表征晶体和N相的溶液结构。该系统具有不同大小的聚苯乙烯-嵌段-聚（l-丙交酯）（PS- b - PLLA）嵌段共聚物单晶（BCSC）分散在p中-二甲苯。这些晶体的形状为截头菱形，有效直径范围为550至4000 nm，均匀干厚度为18.0 nm。由于拴系PS层的对比度较低，使用具有9-10 nm核心层的圆盘模型可以简化溶液中单个晶体的散射。准备用石英细毛细管填充的BCSC悬浮液以监测结构信息。各向同性相的SAXS测量结果显示出很强的面对面相关性，表明血小板在溶液中形成小的堆积簇。各向同性相因此是单晶和堆叠的多层簇的共存。面对面间距d在N相中的，约为75-90 nm，随着晶体尺寸的增加而略有增加。对于给定的系统，在当前实验条件下，间距不会随着浓度的增加而变化。最后，由于该系统的侧向吸引力，还讨论了N相内层状畴的可能形成。这些结果证明了极性晶体PLLA嵌段之间的横向吸引对N相形成的重要性：BCSC通过横向吸引自组装成更大的薄片，这进一步增强了I–N跃迁。
更新日期：2021-02-23
中文翻译：
小角度X射线散射研究板状半结晶嵌段共聚物单晶的向列相
结晶嵌段共聚物已用于制备具有良好控制的尺寸，形状和尺寸分布的板状胶体体系。新型板状胶体颗粒悬浮液的各向同性向向列相（I–N）相变已有报道。在这项工作中，我们专注于使用小和超小角度X射线散射技术（SAXS / USAXS）表征晶体和N相的溶液结构。该系统具有不同大小的聚苯乙烯-嵌段-聚（l-丙交酯）（PS- b - PLLA）嵌段共聚物单晶（BCSC）分散在p中-二甲苯。这些晶体的形状为截头菱形，有效直径范围为550至4000 nm，均匀干厚度为18.0 nm。由于拴系PS层的对比度较低，使用具有9-10 nm核心层的圆盘模型可以简化溶液中单个晶体的散射。准备用石英细毛细管填充的BCSC悬浮液以监测结构信息。各向同性相的SAXS测量结果显示出很强的面对面相关性，表明血小板在溶液中形成小的堆积簇。各向同性相因此是单晶和堆叠的多层簇的共存。面对面间距d在N相中的，约为75-90 nm，随着晶体尺寸的增加而略有增加。对于给定的系统，在当前实验条件下，间距不会随着浓度的增加而变化。最后，由于该系统的侧向吸引力，还讨论了N相内层状畴的可能形成。这些结果证明了极性晶体PLLA嵌段之间的横向吸引对N相形成的重要性：BCSC通过横向吸引自组装成更大的薄片，这进一步增强了I–N跃迁。
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