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Issue 36, 2013
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A phase diagram of neutral polyampholyte – from solution to tough hydrogel

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Abstract

Our recent study has revealed that neutral polyampholytes form tough physical hydrogels above a critical concentration Cm,c by forming ionic bonds of wide strength distribution. In this work, we systematically investigate the behavior of a polyampholyte system, poly(NaSS-co-DMAEA-Q), randomly copolymerized from oppositely charged monomers, sodium p-styrenesulfonate (NaSS) and acryloyloxethyltrimethylammonium chloride (DMAEA-Q) without and with a slight chemical cross-linking. A phase diagram of formulation has been constructed in the space of monomer concentration Cm and cross-linker density CMBAA. Three phases are observed for the as-synthesized samples: homogeneous solution at dilute Cm, phase separation at semi-dilute Cm, and homogenous gel at concentrated Cm. Above a critical Cm,c, the polyampholyte forms a supramolecular hydrogel with high toughness by dialysis of the mobile counter-ions, which substantially stabilizes both the intra- and inter chain ionic bonds. The presence of the chemical cross-linker (CMBAA > 0) brings about a shift of the tough gel phase to lower Cm,c. The tough polyampholyte gel, containing ∼50 wt% water, is highly stretchable and tough, exhibits fracture stress of σb ∼ 0.4 MPa, fracture strain of εb ∼ 30, and the work of extension at fracture Wext ∼ 4 MJ m−3. These values are at the level of most tough soft materials. Owing to the reversible ion bonds, the poly(NaSS-co-DMAEA-Q) gels also exhibit complete self-recovery (100%) and high fatigue resistance upon repeated large deformation.

Graphical abstract: A phase diagram of neutral polyampholyte – from solution to tough hydrogel

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Publication details

The article was received on 04 Jun 2013, accepted on 16 Jul 2013 and first published on 17 Jul 2013


Article type: Paper
DOI: 10.1039/C3TB20790K
Citation: J. Mater. Chem. B, 2013,1, 4555-4562
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    A phase diagram of neutral polyampholyte – from solution to tough hydrogel

    A. B. Ihsan, T. L. Sun, S. Kuroda, Md. A. Haque, T. Kurokawa, T. Nakajima and J. P. Gong, J. Mater. Chem. B, 2013, 1, 4555
    DOI: 10.1039/C3TB20790K

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