Patent ID: 7517472

Claim:
A composition comprising a blend of a) a luminescent polymer having a weight average molecular weight (M w ) of at least 20,000 and b) a viscosity modifier that 1) is a solid at room temperature; 2) has a M w of less than 5000; 3) has a luminescent emission maximum of 350 to 480 nm; 4) does not substantially diminish charge transporting properties of the combination of the modifier and the polymer; and 5) contains no exocyclic conjugated double bonds; wherein the modifier and its concentration in the blend are selected so that the blend exhibits a luminescent emission maximum that is within 20 nm of the luminescent emission maximum of the polymer alone, and the viscosity modifier contains no O, N, or S atoms with delocalized unshared pairs of electrons, and wherein the viscosity modifier is selected from the group consisting of 1,2,4-tris(9,9-dibutylfluorene)benzene and 1,3,5-tris(9,9-dibutylfluorenyl)benzene.