Coacervation-Based Method for Constructing a Multifunctional Strain-Stiffening Crystalline Polyvinylamine Hydrogel

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Strain-stiffening hydrogels mimic human skin's self-protection mechanism.
• Poly(vinyl alcohol) (PVA) hydrogels offer limited tunable properties for strain-stiffening.
• Polyvinylamine (PVAm) presents higher reactivity for multifunctional hydrogels but faces challenges in crystallization.

Purpose of the Study:

• To develop a facile method for creating multifunctional, strain-stiffening PVAm hydrogels.
• To overcome the difficulties in forming crystalline PVAm hydrogels due to amine ionization.
• To integrate strain-stiffening with self-healability, self-adhesion, and ionic conductivity.

Main Methods:

• A one-pot coacervation method was devised using PVAm.
• Coacervation occurred between PVAm chains, leading to aggregated and loose phases.
• This strategy reduced amine-water binding energy to induce crystallinity and desired properties.

Main Results:

• The PVAm hydrogel exhibited excellent stretchability (~1300%), toughness (227 kPa), and a ~10-fold increase in strain-stiffening.
• The material demonstrated significant self-adhesion (90 J m⁻²) and self-healability (~80% healing efficiency).
• The hydrogel also possessed ionic conductivity (0.22 mS m⁻¹).

Conclusions:

• The one-pot PVAm coacervation method successfully induces crystallinity and strain-stiffening.
• This approach enables the creation of multifunctional hydrogels with properties relevant to ionic skin.
• The strategy offers a new pathway for designing advanced skin-mimic materials.