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Polymers 2017, 9(9), 412; https://doi.org/10.3390/polym9090412

Surface Active to Non-Surface Active Transition and Micellization Behaviour of Zwitterionic Amphiphilic Diblock Copolymers: Hydrophobicity and Salt Dependency

1
Department of Polymer Chemistry, Kyoto University, Katsura, Kyoto 615-8510, Japan
2
Centre for Research and Development, Department of Physics, PRIST University, Vallam, Thanjavur 613 403, Tamil Nadu, India
*
Author to whom correspondence should be addressed.
Received: 8 August 2017 / Revised: 29 August 2017 / Accepted: 30 August 2017 / Published: 5 September 2017
(This article belongs to the Special Issue Polymer Micelles)
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Abstract

We have synthesized a range of zwitterionic amphiphilic diblock copolymers with the same hydrophilic block (carboxybetaine) but with different hydrophobic blocks (n-butylmethacrylate (n-BMA) or 2-ethylhexylacrylate (EHA)) by the reversible addition–fragmentation chain transfer (RAFT) polymerization method. Herein, we systematically examined the role of hydrophobicity and salt concentration dependency of surface activity and micellization behaviour of block copolymer. Transition from surface active to non-surface active occurred with increasing hydrophobicity of the hydrophobic block of block copolymer (i.e., replacing P(n-BMA) by PEHA). Foam formation of block copolymer slightly decreased with the similar variation of the hydrophobic block of block copolymer. Block copolymer with higher hydrophobicity preferred micelle formation rather than adsorption at the air–water interface. Dynamic light scattering studies showed that block copolymer having P(n-BMA) produced near-monodisperse micelles, whereas block copolymer composed of PEHA produced polydisperse micelles. Zimm plot results revealed that the value of the second virial coefficient (A2) changed from positive to negative when the hydrophobic block of block copolymer was changed from P(n-BMA) to PEHA. This indicates that the solubility of block copolymer having P(n-BMA) in water may be higher than that of block copolymer having PEHA in water. Unlike ionic amphiphilic block copolymer micelles, the micellar shape of zwitterionic amphiphilic block copolymer micelles is not affected by addition of salt, with a value of packing parameters of block copolymer micelles of less than 0.3. View Full-Text
Keywords: non-surface activity; self-assembly; hydrophobicity; zwitterionic amphiphilic block copolymer; light scattering; polymer micelle non-surface activity; self-assembly; hydrophobicity; zwitterionic amphiphilic block copolymer; light scattering; polymer micelle
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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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Murugaboopathy, S.; Matsuoka, H. Surface Active to Non-Surface Active Transition and Micellization Behaviour of Zwitterionic Amphiphilic Diblock Copolymers: Hydrophobicity and Salt Dependency. Polymers 2017, 9, 412.

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