Opto‐Mechanical Characterization and Antimicrobial Performance of iPP/TiO ₂ and iPP/Ag Nanocomposite Fibers: A Combined Stokes Polarimetry and Birefringence Analysis

This study investigates the opto-mechanical properties and antimicrobial performance of isotactic polypropylene (iPP) nanocomposite fibers reinforced with TiO₂ and Ag nanoparticles at 2.5 wt% loading. A modified Mach-Zehnder interferometer integrated with Stokes polarimetry was developed for direct birefringence quantification using S₂ and S₃ parameters, with three-dimensional optical anisotropy profiles reconstructed via inverse Abel transform. Antimicrobial evaluation against four clinically relevant pathogens demonstrated superior performance for iPP/Ag nanocomposites (78.4 ± 8.4% growth inhibition) compared to iPP/TiO₂ systems (66.8 ± 7.3%). Birefringence analysis revealed significant enhancement upon nanoparticle incorporation, with iPP/TiO₂ fibers showing 39% higher birefringence (0.0146) compared to pristine iPP (0.0105), whereas iPP/Ag systems exhibited 26% enhancement (0.0132). Progressive mechanical drawing demonstrated that iPP/TiO₂ nanocomposites achieved superior drawability (maximum draw ratio 4.2) with exceptional birefringence development (0.0459), surpassing iPP/Ag systems (draw ratio 3.9, birefringence 0.0394) and pristine iPP fibers (draw ratio 3.4, birefringence 0.0312). These findings establish comprehensive structure-property relationships for advanced nanocomposite fiber systems with tailored multifunctional properties.