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Interplay of Solvation and Size Effects Induced by the Counterions in Ionic Block Copolymers on the Basis of Hofmeister Series
Author(s) -
Luo Haipeng,
Tang Qiuju,
Zhong Jiaxing,
Lei Zhentao,
Zhou Junyi,
Tong Zaizai
Publication year - 2019
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201800508
Subject(s) - counterion , chemistry , copolymer , micelle , solvation , hofmeister series , ionic bonding , aqueous solution , polymer chemistry , chemical physics , polystyrene , ionic radius , bromide , chemical engineering , ion , inorganic chemistry , organic chemistry , engineering , polymer
Abstract Two ionic block copolymers with different lengths of hydrophilic segments, polystyrene‐ b ‐poly(quaternized 4‐vinylpyridine)/ethyl bromide, are prepared by sequential reactions. They are originally self‐assembled into so‐called “large compound micelles” in aqueous solution. After ion exchange of Iˉ, SCN,ˉ and PF 6 ˉ for Brˉ, morphological transitions are controlled by a competition of solvation and size effects of the newly introduced counterions. The solvation effect is dominated in a relatively short corona‐forming block. Thus, sphere‐to‐wormlike particles, sphere‐to‐vesicle, and sphere‐to‐precipitate transitions are observed. In contrast, due to a long corona‐forming block, size effects become more profound after adding SCNˉ, thereby no morphological transition occurs. A morphological transition is characterized after partial exchange of Iˉ for Brˉ for both diblocks. A sphere‐to‐wormlike particles transition is observed only after most Brˉ is replaced by Iˉ. This work extends the understanding of morphological regulation through simple ion exchange and encourages rational design of nano‐assemblies.