Synthesis and Self-Association of Stimuli-Responsive Diblock Copolymers by Living Cationic Polymerization

The living cationic polymerization of several functional monomers in the presence of an added base is investigated as a possible preparation of a new series of water‐soluble or stimuli‐responsive copolymers. Under appropriate conditions, the polymerization allows the selective preparation of polymer...

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Bibliographic Details
Published in:Macromolecular symposia. 2004-08, Vol.215 (1), p.151-164
Main Authors: Aoshima, Sadahito, Sugihara, Shinji, Shibayama, Mitsuhiro, Kanaoka, Shokyoku
Format: Article
Language:English
Subjects:
Cationic polymerization
Copolymers
Dynamics
Gelation
living cationic polymerization using an added base
macrolattice formation of the micelles
Monomers
Polymerization
Polymers
Segments
star-shaped polymers
stimuli-induced self-association
stimuli-responsive block copolymer
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Summary:The living cationic polymerization of several functional monomers in the presence of an added base is investigated as a possible preparation of a new series of water‐soluble or stimuli‐responsive copolymers. Under appropriate conditions, the polymerization allows the selective preparation of polymers with various shapes and different sequence distributions of monomer units, including stimuli‐responsive block copolymers, gradient copolymers, poly(vinyl alcohol) graft copolymers, and star‐shaped polymers. The stimuli‐induced self‐association of the diblock copolymers is also examined. An aqueous solution of the diblock copolymer with a thermo‐sensitive segment undergoes rapid physical gelation upon warming to the critical temperature to give a transparent gel, and returns sensitively to the solution state upon cooling. The sharp transition of stimuli‐responsive segments with highly controlled primary structure turns out to play an important role in the self‐association. Small‐angle neutron scattering, dynamic light scattering, and electron microscopy studies reveal that the physical gelation involves a thermosensitive micellization of diblock copolymers (core size: 18‐20 nm) and subsequent micelle macrolattice formation (bcc symmetry). Based on the gelation mechanism, several stimuli‐responsive gelation systems are achieved using other stimuli such as the addition of a selective solvent or compound, cooling, pH change, and irradiation with ultraviolet light.
ISSN:1022-1360
1521-3900
DOI:10.1002/masy.200451113