Single white polymers based on simple diarylmaleimdes: Polymeric structure and electroluminescent properties

Two kinds of novel single white polymers, lateral-chain type and star-like type, were designed and synthesized by introducing di( p -methoxyphenyl)maleimide (λ em  = 540 nm) or dithienylmaleimide (λ em  = 558 nm) guest into the side chain of linear polyfluorene (LPF-TMs and LPF-PMs), and diphenylmaleimide (λ em  = 500 nm) guest into the core of star-like polyfluorene (SPF-PMs). By adjusting the feed ratio of maleimide and fluorene units, the resulting single white polymers exhibited a dual emission including blue emission (ca 430 nm) from polyfluorene host and yellow (ca 536 nm) emission from diarylmaleimide guest. Their electroluminescent properties were investigated in the single-emitting-layer devices fabricated by solution process with the configuration of ITO/PEDOT:PSS/polymer/TPBI/LiF/Al. Compared with main-chain type polymers, LPF-PMs and SPF-PMs displayed better electroluminescent performance with the maximal current efficiency of 8.77 cd/A and 10.30 cd/A, respectively. Due to the balanced blue and yellow emission, LPF-TM03 containing 0.3% guest get the relatively pure white light with CIE coordinates value of (0.31,0.33). The results indicate that diarylmaleimide is a kind of utility guest to construct easily synthesized, structurally diverse and highly efficient white polymers.