Comparative Optical Analysis of Polyphenylene Sulfide and 2-Mercaptopyridine Derivatives: A Raman and UV–VIS Spectroscopic Approach Towards Nonlinear Optical Applications

Abstract

This comparative study evaluates the nonlinear optical (NLO) properties of two polymeric systems—polyphenylene sulfide (PPS) and 2-mercaptopyridine (2-MP), an aromatic polysulphide derivative. Raman and UV–VIS spectroscopy are employed to explore molecular vibrational features and electronic transitions that govern their NLO behavior. PPS, a semi crystalline thermoplastic polymer, exhibits poor SHG efficiency due to its centrosymmetric geometry, while 2-MP displays distinct S–S and C–S vibrational modes and a smaller band gap, facilitating enhanced second harmonic generation. The results highlight the critical influence of molecular symmetry, conjugation, and vibrational dynamics in designing effective NLO materials.