Restraining the associations of anthracene fluorophore by chemically linking to poly(methyl methacrylate)

Abstract

Associations (dimer or aggregate) of anthracene (An) fluorophores tend to interrupt the monomer emission and reduce the quantum yield (F PL ); therefore, poly(methyl methacrylate) (PMMA) chain was used in this study to chemically link to anthracene and to block the mutual associations among the anthracene fluorophores. With this aim, the target polymers were prepared by anionic polymerizations with 9,10-dibromoanthracene/s-butyllithium as initiating system to proceed polymerizations of methyl methacrylate (MMA) directly or in the presence of 1,1-diphenylethylene (DPE). Use of DPE before addition of MMA produces stable initiating anionic species and avoids potential side reactions during polymerization; however, it also introduces four b-phenylene rings around the central anthracene ring, which interfere with the corresponding emission pattern and reduce the F PL (32%) value due to potential interactions between phenylene rings and anthracene. On the contrast, polymerization without participation of DPE results in polymer with central anthracene ring directly connected to two PMMA chains, which gives clean vibronic emission pattern with limited association emissions and enhanced F PL (52%) value. Physical blending of anthracene by PMMA is less efficient to restrain the associations and results in a film of lower F PL (20%).