Coacervate Phase Evolution and Membrane Formation in Natural Seawater

Area of Science:

• Materials Science
• Biomaterials Engineering
• Polymer Chemistry

Background:

• Marine organisms utilize protein self-assembly for biomineralization.
• Understanding microstructure evolution in these processes is crucial for biomimetic material design.
• Current polymer processing often relies on harsh conditions like organic solvents and heat.

Purpose of the Study:

• To develop a synthetic polymer system that mimics the self-assembly of mussel holdfast proteins.
• To investigate the mechanisms of microstructure formation and maturation in a marine-like environment.
• To enable solvent-free and heat-free fabrication of hierarchically porous materials.

Main Methods:

• Design and synthesis of an amphiphilic, fluorescent polymer (PECHIA) with a polyepichlorohydrin backbone and 1-imidazolium acetonitrile grafts.
• Extrusion of aqueous PECHIA solutions into simulated seawater to induce interfacial condensation via cation-dipole interactions.
• Observation of inverse coacervation and nitrile cyclization catalyzed by seawater alkalinity for material solidification.

Main Results:

• PECHIA undergoes inverse coacervation in high-salinity seawater, forming droplets within the polymer phase.
• Seawater's alkalinity catalyzes nitrile cyclization, leading to time-dependent solidification of PECHIA.
• Hierarchically porous membranes, analogous to mussel plaques, were formed without organic solvents or heating.
• Template-free production of hollow spheres and fibers was achieved across a range of salinities.

Conclusions:

• The PECHIA polymer effectively captures critical processing attributes of mussel holdfast proteins.
• This biomimetic approach enables sustainable and versatile fabrication of complex porous structures.
• The findings offer a novel pathway for creating advanced materials inspired by marine biomineralization.