Superior Strong and Stiff Alginate Fibers by Entanglement-Enhanced Stretching

The current environment crisis has forced a compelling trend of rapidly expanding degradable biomass polymers to take over petrochemical polymers. Exploiting new high-performance biomass materials has become urgent but is greatly challenging. Here, we develop a series of high-performance alginate fibers by a new entanglement-enhanced stretching strategy and examine its mechanism. The high stretch ratio exerted during spinning facilitates high structural orders and crystallinity of fibers, which exhibit a high modulus of 50.4 GPa and superior tensile strength of 1.05 GPa, outperforming most regenerated biomass fibers. Shear and extensional rheology shows that ultrahigh-molecular weight polyelectrolytes with high flexibility increase the entanglement density and extensional relaxation time of the spinning solution. Tensile tests of gel filaments formed during sequential coagulation demonstrate that gels with ultrahigh-molecular weight polyelectrolytes in the range of 3–9 wt % exhibit high strength and elongation at break due to the higher entanglement density and hindrance of cross-link formation, which is consistent with the maximum stretch ratio that can be exerted to the filament during wet spinning. This strategy of introducing “inert” polymer additives with ultrahigh molecular weight can also be adopted to fabricate alginate industrial filaments to compete with synthetic polymer staple filaments and other biomass fibers with upgrading strength to extend the source of high-performance biomaterials.