Superior Strong and Stiff Alginate Fibers by Entanglement-Enhanced Stretching

The current environment crisis has forced a compellingtrend ofrapidly expanding degradable biomass polymers to take over petrochemicalpolymers. Exploiting new high-performance biomass materials has becomeurgent but is greatly challenging. Here, we develop a series of high-performancealginate fibers by a new entanglement-enhanced stretching strategyand examine its mechanism. The high stretch ratio exerted during spinningfacilitates high structural orders and crystallinity of fibers, whichexhibit a high modulus of 50.4 GPa and superior tensile strength of1.05 GPa, outperforming most regenerated biomass fibers. Shear andextensional rheology shows that ultrahigh-molecular weight polyelectrolyteswith high flexibility increase the entanglement density and extensionalrelaxation time of the spinning solution. Tensile tests of gel filamentsformed during sequential coagulation demonstrate that gels with ultrahigh-molecularweight polyelectrolytes in the range of 3-9 wt % exhibit highstrength and elongation at break due to the higher entanglement densityand hindrance of cross-link formation, which is consistent with themaximum stretch ratio that can be exerted to the filament during wetspinning. This strategy of introducing "inert" polymeradditives with ultrahigh molecular weight can also be adopted to fabricatealginate industrial filaments to compete with synthetic polymer staplefilaments and other biomass fibers with upgrading strength to extendthe source of high-performance biomaterials.