Interplay of the structures and viscoelastic properties of polyampholyte gels with the interlude of neutral blocks

Abstract

Polyampholyte gels with hierarchical structures due to the microphase separation are good candidates for biomaterials and bioengineering due to their unique properties such as self-healing and anti-biofouling. However, how to precisely control their microstructures and viscoelastic properties is yet to be explored. By introducing the acrylamide neutral blocks, we have quantitively tuned the microstructures and viscoelastic properties of polyampholyte gels. With the interlude of more acrylamide neutral blocks, the size and density of the ionic clusters become smaller, leading to a shorter relaxation time. Very small angle neutron scattering results show that the interlude of hydrophilic acrylamide neutral blocks will act as defects to suppress the phase separation and make the microphase separated domains become smaller. In the yielding measurements, the reversible dissociation–association dynamical behavior of the ionic bonds can protect the gels from yielding, exhibiting excellent self-healing properties. The interlude of acrylamide neutral blocks would act as defects to disrupt the formation of ionic bonds, thus making the yielding point decrease. Finally, the impact of different swelling methods on the viscoelastic properties was also studied. Only for gels with intermediate ionic bond strength, can the association–dissociation collective dynamical behavior of the ionic bonds be observed, so they can exhibit excellent self-healing properties. When the ionic bond strength is too strong or too weak, the self-healing properties would disappear. Our work enables us to mimic biological tissues such as mucus, vitreous humor, and nucleus pulposus with desirable viscoelastic properties and self-healing behaviors.