Symmetry-Dictated Mesophase Formation and Phase Diagram of Perfluorinated Polyhedral Oligomeric Silsesquioxanes

Autor:	Shuguang Yang, Guang-Zhong Yin, Shuaiyuan Han, Xian Xu, Yu Shao, Qiang Fu, Wen-Bin Zhang, Di Han
Rok vydání:	2019
Předmět:	chemistry.chemical_classification Phase transition Materials science Polymers and Plastics Organic Chemistry Mesophase Silsesquioxane Inorganic Chemistry Crystallography chemistry.chemical_compound chemistry Liquid crystal Phase (matter) Materials Chemistry Lamellar structure Alkyl Phase diagram
Zdroj:	Macromolecules. 52:2361-2370
ISSN:	1520-5835 0024-9297
Popis:	We report the symmetry-dictated mesophase formation and phase diagram of a series of T8-polyhedral oligomeric silsesquioxane (POSS) derivatives bearing perfluoroalkyl chains and hydroxyl alkyl groups. The phase structures and phase behaviors of these molecular Janus particles were studied by DSC, POM, FT-IR, and WAXD experiments. It was found that introducing one hydroxyl alkyl group leads to a decreased crystal melting point, and incorporating two hydroxyl alkyl groups at different POSS positions causes the formation of lamellar liquid crystal mesophases with feature sizes and transition temperatures that depend on the symmetry of these regioisomers. Interestingly, installing only one substituent with two hydroxyl groups leads to monotropic phase transitions, where the mesophase appears only upon cooling from the isotropic melt within the narrow supercooling window. Phase diagrams were systematically constructed for these compounds and understood based on the fine influence of symmetry on their possible ...
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::8d02d32e28fac43d89d6f9a8942f6e45 https://doi.org/10.1021/acs.macromol.9b00138 Zobrazit plný text záznamu