New fluorescence labeling isotactic polypropylenes as a tracer: a proof of concept

Propylene-co-N-pentenyl-carbazole copolymers P(P-co-PK)s containing a low amount of isolated PK units were prepared by using the isospecific homogeneous Ziegler-Natta (Z-N) catalytic system rac-dimethylsilylbis(1-indenyl)zirconium dichloride/methylaluminoxane (MAO) with the aim to achieve fluorescent polypropylenes (PPs). Such materials could find applications both for the detection based on fluorescent tagging of PP-derived microplastic pollutants in organic tissues and as fluorescent markers of commercial i-PP allowing its identification during the separation phase of the plastic recycling process. P(P-co-PK)s are optically active and exhibit fluorescence emission when excited at 300 nm. They also show chemical and physical properties very close to those of commercial i-PPs. The P(P-co-PK) X-ray diffraction patterns match that of the i-PP α form, while P(P-co-PK) thermograms present endothermic peaks around 135 °C due to i-PP block melting. Microplastics from P(P-co-PK)s were prepared and tested as fluorescent markers to investigate the biological effect of plastics dispersed in an aquatic environment on leeches (Hirudo verbana). The first results indicate that P(P-co-PK)s are suitable to mimic PP-derived microplastic pollutants in animal tissues. Moreover, preliminary studies conducted on P(P-co-PK)/commercial i-PP blends show that P(P-co-PK)s can also be used as fluorescent dyes for i-PP identification during the separation step of the plastic recycling process.