Green processing of polyelectrolyte complex fibers

PECs have been recognized as promising material systems for various applications, ranging from water purification, underwater adhesives, and functional artificial fibers. In this thesis, we focus on the green processing of PEC fibers, by exploring different (bio)polymer complexes and different spinning strategies. We first described a green processing route to fabricate wet-spun PSSNa/PDADMAC fibers and particularly emphasized the importance of the post-treatment, which was essential to reduce internal defects and improve their mechanical performance. In the next chapter, we replaced PDADMAC with positively charged semi-crystalline polypeptides to investigate if the molecular orientation could be improved by introducing crystallinity. Homogeneous keratin/PSSNa coacervates were prepared that were directly used for dry-spinning. The obtained keratin/PSSNa fibers exhibited good mechanical properties, humidity responsiveness, and ion-conductivity, but exhibited a non-oriented amorphous structure. To obtain molecular alignment, keratin coacervates were prepared without the addition of any other polyelectrolytes by lowering the pH. These keratin coacervates enabled the fabrication of stretched keratin fibers with high mechanical performance and molecular alignment along the fiber axis. The biopolymer coacervates developed here represented a promising processing tool to shape and compound biopolymers into final products. Lastly, instead of typical complexation between polyanions and polycations, the metal cations Zr4+ were applied to crosslink the PBDT chains through electrostatic interactions, creating a physical network consisting of non-covalent interactions. We demonstrated that water-soluble PBDT with a rigid backbone can be considered a useful filler in biomaterials and the complexation with Zr4+ offered a great opportunity to improve material mechanical properties.