Blend of viscosity modifier and luminescent compound

Abstract

The present invention relates to a composition comprising a blend of a luminescent polymer and a low molecular weight (<5000 amu) viscosity modifier, which has an emission maximum in the range of 350-480 nm, contains no exocyclic double bonds, and modifies the viscosity of the polymer without substantially altering emissive properties of the neat polymer. Modification of viscosity without concomitant modification of emissive properties is desirable where the polymer is already tuned to emit at the desired wavelength.

What is claimed is:  
     
         1 . 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.  
   
     
     
         2 . The composition of  claim 1  wherein the viscosity modifier does not contain any O, N, or S atoms with delocalized unshared pairs of electrons.  
     
     
         3 . The composition of  claim 1  which further includes a solvent for the luminescent polymer and the viscosity modifier.  
     
     
         4 . The composition of  claim 3  wherein the solvent is selected from the group consisting of toluene, cyclohexylbenzene, xylenes, mesitylene, tetralin, decalin, methyl benzoate, isopropyl biphenyl, and anisole, and combinations thereof.  
     
     
         5 . The composition of  claim 1  wherein the luminescent emission maximum of the blend is within 10 nm of the luminescent emission maximum of the polymer.  
     
     
         6 . The composition of  claim 5  wherein the luminescent emission maximum of the blend is within 5 nm of the luminescent emission maximum of the polymer.  
     
     
         7 . The composition of  claim 1  wherein the viscosity modifier is a fluorene oligomer.  
     
     
         8 . The composition of  claim 1  wherein the viscosity modifier is selected from the group consisting of mono-, bis-, and tris-9,9-disubstituted fluorenes; fluorenylidenes, and trifluorenylbenzenes.  
     
     
         9 . The composition of  claim 8  wherein the viscosity modifier is selected from the group consisting of 1,2,4-tris(9,9-bisbutylfluorene)benzene and 1,3,5-tris(9,9-bisbutylfluorene)benzene.  
     
     
         10 . The composition of  claim 1  wherein the polymer contains structural units of monomers selected from the group consisting of 9,9-disubstitutedfluorene, 2-methoxyl-5-(2′-ethylhexyl)phenylenevinylene; 2,5-dioctyloxy- 1,4-phenylenevinylene; 2-silyl- 1,4-phenylenevinylene; 2,5-disilyl- 1,4-phenylenevinylene; 3-alkylthiophene; 2,5-dialkyl- 1,4-phenylenevinylene; 2,5-dialkoxyphenylene; 2,5-dialkylphenylene; and N-vinylcarbazole.  
     
     
         11 . The composition of  claim 1  wherein the polymer contains structural units of a first monomer selected from the group consisting of 9,9-dialkylfluorene, 9,9-diarylfluorene, and 9,9-aralkylfluorene, and a second monomer selected from the group consisting of substituted and unsubstituted thiophenes, dithiophenes, benzodiathiazoles, oxazoles, oxadiazoles, benzoxazoles, dibenzofurans, benzothiophenes, dibenzothiophenes, dibenzosiloles, benzidines, diarylamines, triarylamines, benzenes, biphenylenes, naphthalenes, anthracenes, phenanthrenes, styrenes, quinolines, and stilbenes.  
     
     
         12 . 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 from 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; and  
   c) a solvent for the luminescent polymer and the viscosity modifier;    wherein the relative amounts of the modifier and the polymeric compound in the blend are such that the blend exhibits a luminescent emission maximum that is within 10 nm of the luminescent emission maximum of the polymer alone.    
     
     
         13 . The composition of  claim 12  wherein the luminescent polymer includes structural units of a 9,9-disubstituted fluorene and a monomer selected from the group consisting of benzidines dithiophenes, and benzothiadiazoles.  
     
     
         14 . The composition of  claim 13  wherein the solvent is selected from the group consisting of toluene, cyclohexylbenzene, xylenes, mesitylene, tetralin, decalin, methyl benzoate, isopropyl biphenyl, and anisole.  
     
     
         15 . The composition of  claim 14  wherein the structural units of a 9,9-disubstituted fluorene include substituents at the 9,9-position are selected from the group consisting of C 4 -C 12  alkyl, C 4 -C 12 -alkoxy, substituted phenyl, unsubstituted phenyl, substituted biphenyl, and unsubstituted biphenyl.