An investigation into the hexagonal phases formed in high-concentration dispersions of well-defined cylindrical block copolymer micelles

This paper presents a detailed analysis of the structure of the hexagonal phase of poly(ferrocenylsilane) (PFS)-based cylindrical micelles found at concentrations above ca. 5 wt. % in non-polar solvents such as decane. Small-angle X-ray scattering indicated that the hexagonal order is not long-range. In all samples, deviations in the lower order peak positions were observed with respect to those expected for a perfect hexagonal lattice, with the degree of deviation correlating with micelle length. Furthermore, analysis of the peak shapes and peak widths suggests that the phase possesses intermediate translational order similar. to the hexatic phase. The observed features can be reproduced by amending Hosemann’s paracrystal theory to include a distribution of lattice parameters to model well and poorly condensed regions. It is proposed that this distribution arises due to the bending and intertwining of individual micelles in a hexagonal lattice, resulting in a kinetically trapped phase that is initially neither perfectly hexagonal nor canonically hexatic but which anneals over time towards a perfect hexagonal lattice.

本论文针对在癸烷等非极性溶剂中浓度约高于5 wt.%时形成的聚二茂铁硅烷（poly(ferrocenylsilane), PFS）基圆柱胶束的六方相结构展开了详细分析。小角X射线散射（Small-angle X-ray scattering）结果表明，该六方有序结构并非长程有序。所有样品均出现与完美六方晶格预期峰位存在偏移的低阶散射峰，且偏移程度与胶束长度相关。进一步对峰形与峰宽的分析显示，该相具有类似六方向列相（hexatic phase）的中间态平移序。通过修正霍塞曼副晶理论（Hosemann’s paracrystal theory），引入晶格参数分布以模拟致密与疏松区域，可复现观测到的实验特征。研究认为，该晶格参数分布源于六方晶格中单个胶束的弯曲与缠结，最终形成动力学俘获相：该相初始既非完美六方结构，也非常规六方向列相，但可随时间退火趋近于完美六方晶格。