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Guest‐Responsive Covalent Frameworks by the Cross‐Linking of Liquid‐Crystalline Salts: Tuning of Lattice Flexibility by the Design of Polymerizable Units
Author(s) -
Ishida Yasuhiro,
Sakata Hiroaki,
Achalkumar Ammathnadu S.,
Yamada Kuniyo,
Matsuoka Yuki,
Iwahashi Nobutaka,
Amano Sayaka,
Saigo Kazuhiko
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201102422
Subject(s) - carboxylic acid , polymer , polymerization , alkyl , amphiphile , monomer , covalent bond , chemistry , polymer chemistry , desorption , amine gas treating , salt (chemistry) , materials science , chemical engineering , adsorption , organic chemistry , copolymer , engineering
Cross‐linked polymers prepared by the in‐situ polymerization of liquid‐crystalline salts were found to work as solid‐state hosts with a flexible framework. As a component of such hosts, four kinds of polymerizable amphiphilic carboxylic acids bearing alkyl chains with acryloyloxy (A), dienyl (D), and/or nonreactive (N) chain ends (monomeric carboxylic acids; M AAA , M ANA , M DDD , and M DND ) were used. The carboxylic acids were mixed with an equimolar amount of a template unit, (1 R ,2 S )‐norephedrine (guest amine; G RS ), to form the corresponding salts. Every salt exhibited a rectangular columnar LC phase at room temperature, which was successfully polymerized by 60 Co γ‐ray‐induced polymerization without serious structural disordering to afford the salt of cross‐linked carboxylic acid (polymeric carboxylic acid; P AAA , P ANA , P DDD , and P DND ) with G RS . Owing to the noncovalency of the interactions between the polymer framework P and the template G RS , the cross‐linked polymers could reversibly release and capture a meaningful amount of G RS . In response to the desorption and adsorption of G RS , the cross‐linked polymers dramatically switched their nanoscale structural order. A systematic comparison of the polymers revealed that the choice of polymerizable groups has a significant influence on the properties of the resultant polymer frameworks as solid‐state hosts. Among these polymers, P DDD was found to be an excellent solid‐state host, in terms of guest‐releasing/capturing ability, guest‐recognition ability, durability to repetitive usage, and unique structural switching mode.