Environmentally Benign Blue Emissive Films from Host-Dopant Interaction of PLA-Bischalcone Combination with High UV Endurance

AJ Pai and BK Sarojini and KR Harshitha and A Soldera, JOURNAL OF POLYMERS AND THE ENVIRONMENT, 30, 373-384 (2022).

DOI: 10.1007/s10924-021-02196-1

This work reports the fabrication of blue luminescent bioplastic PLA films on doping with 4-chloro and 4-fluoro substituted bisarylidene cyclohexanone derivatives A and B. The successful doping of A and B to host matrix was evidenced by spectroscopic and analytical methods. The appearance of an absorption band at 1665 cm(-1) owing to the conjugated alkene stretching frequency for bischalcones approved the presence of guest molecules. Similarly, the crystallinity of the films was improved by the addition of dopants above 2%. Molecular dynamics simulations of mechanical properties for neat PLA for lowest dopant concentration (2%) revealed decrease in Young's modulus and bulk modulus. The doping resulted in bathochromic shift from lambda(max) 290 nm to the range of 335-340 nm with high degree of UV endurance. The PLA/dopant composite films (2-8%) effectively absorbed UVB as well as UVA radiation with promising SPF ranging from 12.71-39.2, 13.26-37.57 and UPF from 17.14-902.50, 9.39-197.01 for dopant A and B respectively. The photoluminescence emission maxima were observed in the blue region at 461 nm and 463 nm for the films doped with A and B. The effective scintillation with large Stoke's shift could be due to J-aggregate alignment of the dopants in the host matrix. The quantitative quantum yield (QY) was found to vary in the range of 0.17-0.42 for A and 0.15-0.46 for B which were comparable with flurophore anthracene with QY 0.27-0.36. Hence, these environmentally benign bioplastic composite materials with high SPF and UPF could find use as wide range UV filtering and also as blue emissive materials.

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