Impact of Cyano-Functional Group on Luminescence of Poly(/'-phenyIenevinyIene) Derivatives: Its Dependence on Conjugation Length

摘要

Soluble cyano-substituted poly(l,3-phenylene vinylene) (8) and poly[(l,3-phenylene vinylene)-a/Mris(l,4-phenylene vinylene)] (10) derivatives have been synthesized and characterized, in comparison with a green-emitting poly[(l,3-phenylene vinylene)-a/?-(l,4-phenylene vinylene)] derivative (9). Chromophores in these polymers are well defined as a result of π-conjugation interruption at adjacent m-phenylene units, leading to blue-emission for film 8 (X,maxft477 nm) and red-emission for film 10 (A.max"640 nm). Optical color tuning in these polymers is achieved through controlled insertion of different oligo(p-phenylene vinylene) length. Although the chromophore of 10 contains only 4.5 phenylene-vinylene units with cyano-substitution on ~50% of the vinylene units, emission Xmx of 10 is comparable to that of cyano-substituted PPV derivative 1. An LED based on 10 emits red-light (644 nm) with an external quantum efficiency of 1.2%.