Polymers, their preparation and uses

Details Polymers, their preparation and uses Polymers, their preparation and uses

2001-01-04

2003-01-28

Truong, Duc (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From boron-containing reactant

C528S422000, C428S690000, C428S917000

Reexamination Certificate

active

06512082

ABSTRACT:

The present invention relates to a conjugated polymer and uses thereof such as in an optical device, and to a process for preparing such a polymer.
Organic electroluminescent devices which use an organic material as the light-emissive material are known in this art. Among organic materials, simple aromatic molecules such as anthracene, perilene and coronene are known to show electroluminescence. U.S. Pat. No. 4,539,507 discloses the use of small molecule organic materials as the light-emissive material, for example, 8-hydroxy quinoline (aluminium). PCT/WO90/13148 discloses an electroluminescent device comprising a semiconducting layer comprising a polymer film as the light-emissive layer which comprises at least one conjugated polymer. In this case, the polymer film comprises a poly(para-phenylene vinylene)(PPV) film.
It is known to use a semiconductive conjugated co-polymer as the light-emissive layer in an electroluminescent device. The semiconductive conjugated copolymer comprises at least two chemically different monomers which, when existing in their individual homopolymer forms, typically have different semiconductor bandgaps. The proportion of the chemically different monomer units in the copolymer can be selected to control the semiconductor bandgap of the copolymer so as to control the optical properties of the copolymer. The extent of conjugation of the copolymer affects the n—n* bandgap of the copolymer. This property may be exploited so that the semiconductor bandgap is modulated to control the wavelength of radiation emitted during luminescence. In addition, by modulating the semiconductor bandgap of the copolymer it is possible to increase the quantum efficiency of the copolymer when exited to luminesce. Furthermore, the semiconductor bandgap is a factor affecting the refractive index of the copolymer.
A method of preparation for aryl-containing conjugated polymers is the Suzuki reaction. U.S. Pat. No. 5,777,070 is directed to attempts to improve the Suzuki reaction to form conjugated polymers from aromatic monomers. The process involves contacting (i) monomers having two reactive groups selected from boronic acid, C
1
-C
6
boronic acid ester C
1
-C
6
borane and combinations thereof with aromatic dihalide functional monomers or (ii) monomers having one reactive boronic acid, boronic acid ester or borane group and one reactive halide functional group with each other. Various aromatic monomers are proposed including those containing triarylamines.
A triarylamine unit has the general structure Ar
1
Ar
2
Ar
3
N where each Ar is the same or different and is an aryl or heteroaryl group.
U.S. Pat. No. 5,633,337, U.S. Pat. No. 5,536,866 and U.S. Pat. No. 5,534,613 each discloses a polymer which comprises triarylamine units. In these polymers, a repeat unit can be defined which comprises a heteroaryl group. However, the heteroaryl group is not directly linked to a nitrogen group. Instead, the heteroaryl group is indirectly linked to a nitrogen group via a phenylene group. In each of these three documents this is an essential feature of the described polymer structure. This structure is essential for achieving the advantageous properties of the described polymers.
U.S. Pat. No. 5,814,244 is concerned broadly with an electroluminescence material comprising one or more polymers which comprise structural units of the formula:
where the symbols and indices have the following meanings:
Ar
1
, Ar
2
, Ar
3
, Ar
4
, Ar
5
, Ar
6
are identical or different, monocyclic and/or polycyclic aryl and/or heteroaryl groups which may be linked via one or more bridges and/or be condensed and may be unsubstituted or substituted, where Ar
1
, Ar
3
, Ar
5
and Ar
6
are each divalent and Ar
2
and Ar
4
are each monovalent;
R
1
is H, a hydrocarbon radical having from 1 to 22 carbon atoms, which may be unsubstituted or substituted, preferably by F, and can also contain heteroatoms, preferably 0, or Ar, where Ar
7
is, independently of Ar
1-6
, as defined for Ar
1-6
;
n is 0, 1 or 2.
The polymers disclosed in this document have low molecular weight and, thus, would have relatively low processability. The presence of vinyl groups in the polymer makes the polymer relatively unstable. The polymers disclosed in this document are not end-capped.
In view of the prior art, there still remains a need for providing new polymers suitable for use in optical devices, particularly electroluminescent devices.
The present invention aims to provide such a new polymer.
Accordingly, in a first aspect, the present invention provides a polymer which comprises triarylamine units. The polymer comprises one or more structural units comprising Ar
h
-NAr
2
where N is directly linked to Ar
h
and in which each Ar is the same or different and comprises a substituted or unsubstituted aryl or heteroaryl group and N is directly linked to Ar
h
.
FIG. 1
shows the structure of an exemplary optical device, which contains layers comprising polymers in accordance with an invention.
It has been found that incorporation of triarylamine units into polymers according to the present invention provides materials with the attractive physical and processing properties of polymers and the ability in their synthesis to select the aryl or heteroaryl groups and their substituents so as to modulate the bandgap of the polymers. This is an important feature, particularly in the design of electroluminescent devices whose efficiency can depend upon the matching of the highest occupied molecular orbital and lowest unoccupied molecular orbital levels of the polymer with the cathode and anode and device host material.
For the purposes of the present invention, the term “polymer” should be interpreted as including linear and branched polymers, oligomers, dendrimers, homopolymers, copolymers and terpolymers.
Preferably, Ar
h
comprises a substituted or unsubstituted nitrogen-containing heteroaryl group. Generally, the heteroaryl group should comprise an electron-deficient heteroatom.
Preferably, each Ar is a substituted or unsubstituted phenyl group. Where the phenyl group is unsubstituted, the polymer is an oligomer. Where the phenyl group is substituted, substituents may be of a nature so as simply to build up the polymer chain and/or to control the bandgap of the polymer or to confer on the polymer solubility in a particular solvent system. Typical solvents include non-polar solvents. For these purposes it is preferred that the polymer bears one or more substituents.
In a first embodiment, the polymer comprises a linear polymer in which the or each structural unit comprises Ar
h
(NAr
2
) Ar
co
, wherein Ar
co
comprises a substituted or unsubstituted aryl or heteroaryl group, Ar
h
comprises a substituted or unsubstituted heteroaryl group and each Ar is the same or different and comprises a substituted or unsubstituted aryl or heteroaryl group. It is preferred that Ar
co
is different from Ar
h
. As discussed above, a substituent on Ar
co
can modulate the semiconductor bandgap of the polymer.
The copolymer where the polymer backbone contains one or more divinylenearylene units may be excluded from the scope of the present invention. Furthermore, a homopolymer where the backbone contains one or more divinylenearylene units can be excluded from the present invention. Generally, this copolymer and this homopolymer are not excluded from the present invention.
In a first aspect of the first embodiment it is preferred that Ar
h
is pendent from the polymer backbone.
In a first subgroup of the first aspect of the first embodiment it is preferred that the polymer comprises a plurality of structural units, having a formula as shown in formula (13):
Most preferably in this first subgroup, the polymer comprises a plurality of structural units, having a formula as shown in formula (8):
In formulae (13) and (8) above, Ar
h
preferably comprises a group as shown in any one of formulae (1) to (4):
In a second subgroup of the first aspect of the first embodiment, it is preferred that the polymer comprises a plurality of structural units having a formula

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