Three derivatives of bis-styrybiphenyl with different degrees of sulfonation to be used as fluorescent whitening agents (FWAs) were synthesized. Studies on their spectroscopic properties were performed using a combination of computational methods. Whitening effects of FWAs and the improved thermal stability of polypropylene (PP) were investigated. The morphology of plastic samples was examined by scanning electronic microscopy (SEM). In order to improve the compatibility between FWA and PP, PP grafted with maleic anhydride (MAH) was applied as compatibilizer. The optical properties were further clarified by the results of frontier molecular orbital modeling, which show that the presence of sulfonic sodium group leads to a red shift of maximum UV absorption wavelength and a low HOMO-LUMO energy band gap. It is observed that the addition of 0.010 wt % of the sulfonated FWA would result in the expected whitening effect as well as improved PP thermal stability, while at or above 0.015 wt %, such effects worsen sharply owing to phase separation. Furthermore, the use of MAH-grafted PP as compatibilizer results in improvement of phase behavior and thermal stability. The study provides new insights into the effect of FWA structure on the properties of PP that are related to the whitening of the material.

A simple and efficient process for direct generation of various S-thiocarbamates is developed by cross-coupling of readily available sulfonyl chlorides with cyclohexyl isocyanide. The yields are excellent and the structures of the generated S-thiocarbamates are characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, and high-resolution mass spectrometry together with X-ray crystallographic analysis. The protocol has the advantages of using easily available reagents, employs inexpensive KI as the reagent, demonstrates good functional group tolerance, and utilizes mild reaction conditions.