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Polymers 2017, 9(8), 367; https://doi.org/10.3390/polym9080367

pH-Induced Association and Dissociation of Intermolecular Complexes Formed by Hydrogen Bonding between Diblock Copolymers

1
Department of Applied Chemistry, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
2
Faculty of Engineering, Fukui University of Technology, 6-3-1 Gakuen, Fukui 910-8505, Japan
*
Authors to whom correspondence should be addressed.
Received: 26 July 2017 / Revised: 12 August 2017 / Accepted: 15 August 2017 / Published: 17 August 2017
(This article belongs to the Special Issue Polymer Micelles)
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Abstract

Poly(sodium styrenesulfonate)–block–poly(acrylic acid) (PNaSS–b–PAA) and poly(sodium styrenesulfonate)–blockpoly(N-isopropylacrylamide) (PNaSS–bPNIPAM) were prepared via reversible addition–fragmentation chain transfer (RAFT) radical polymerization using a PNaSS-based macro-chain transfer agent. The molecular weight distributions (Mw/Mn) of PNaSS–b–PAA and PNaSS–bPNIPAM were 1.18 and 1.39, respectively, suggesting that these polymers have controlled structures. When aqueous solutions of PNaSS–b–PAA and PNaSS–bPNIPAM were mixed under acidic conditions, water-soluble PNaSS–bPAA/PNaSS–bPNIPAM complexes were formed as a result of hydrogen bonding interactions between the pendant carboxylic acids in the PAA block and the pendant amide groups in the PNIPAM block. The complex was characterized by 1H NMR, dynamic light scattering, static light scattering, and transmission electron microscope measurements. The light scattering intensity of the complex depended on the mixing ratio of PNaSS–b–PAA and PNaSS–bPNIPAM. When the molar ratio of the N-isopropylacrylamide (NIPAM) and acrylic acid (AA) units was near unity, the light scattering intensity reached a maximum, indicating stoichiometric complex formation. The complex dissociated at a pH higher than 4.0 because the hydrogen bonding interactions disappeared due to deprotonation of the pendant carboxylic acids in the PAA block. View Full-Text
Keywords: block copolymers; RAFT polymerization; complex; hydrogen bonding interactions; pH-responsive block copolymers; RAFT polymerization; complex; hydrogen bonding interactions; pH-responsive
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Mizusaki, M.; Endo, T.; Nakahata, R.; Morishima, Y.; Yusa, S.-I. pH-Induced Association and Dissociation of Intermolecular Complexes Formed by Hydrogen Bonding between Diblock Copolymers. Polymers 2017, 9, 367.

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