Polymer preparation

Abstract

<heading lvl="0">Abstract of Disclosure< / heading> A process for preparing a conjugated polymer, which comprises polymerizing in a reaction mixture (a) an aromatic monomer having at least two reactive boron derivative groups selected from a boronic acid group, a boronic ester group and a borane group, and an aromatic monomer having at least two reactive halide functional groups; or (b) an aromatic monomer having one reactive halide functional group and one reactive boron derivative group selected from a boronic acid group, a boronic ester group and a borane group, wherein the reaction mixture comprises a catalytic amount of a palladium catalyst, and an organic base in an amount sufficient to convert the reactive boron derivative groups into -B(OH)3- anions.

Description

Cross Reference to Related Applications[0002] This case claims priority to the following, each of which is incorporated by reference:This is a continuation of Application No. 09 / 518,991, filed March 3, 2000,which is a continuation of U.S. Provisional Serial No. 60 / 160,953 filed October 22, 1999; and claims priority from UK Patent Application No. 9905203.7 filed March 5, 1999; andUK Patent Application No. 9925653.9 filed October 29, 1999.Background of Invention[0003] Organic electroluminescent devices are known which employ an organic material for light emission. For example, W090 / 13148 describes such a device comprising a semiconductor layer comprising a polymer film which comprises at least one conjugated polymer situated between electrodes. The polymer film in this case comprises a poly (para-phenylene vinylene) (PPV) film which is capable of light emission when electrons and holes are injected therein. Other polymer layers capable of transporting holes or transporting electrons t...

AI Technical Summary

Benefits of technology

[0024] In another preferred embodiment of the present invention, a tetraalkyl ammonium carbonate or a tetraalkyl ammonium bicarbonate is used as the organic base. Other preferred bases are tetraalkylammonium borates, particularly, tetraethyl ammonium borate. These bases are particularly useful for reducing monomer degradation.

[0027] The use of one equivalent of organic base per boron-derivative functional group has been found to give fair degrees of polymerisation over a relatively long period of time. Preferably, at least 1.5 molar equivalents, further preferably at least 2 molar equivalents, of the organic base per boron-derivative functional group are used. For example, molecular weights over 200,000 have been obtained in a relatively short period of time using 2.26 mole equivalents of organic base per boron-derivative functional group.

[0034] The inventors of the present invention have unexpectedly found that by conducting the reaction using an organic base rather an inorganic base as in US 5,777,070, the polymerization can be carried out with faster reaction times and with better reproducibility. They have also found that the use of an organic base eliminates the problem of foaming and the problem of side-products becoming strongly complexed to the walls of the reaction vessel, whereby the need to utilize specialized reaction vessels is eliminated. In addition, the fact that alkali carbonates or alkali bicarbonates are not required for the reaction also has the additional advantage that it eliminates the need for a final purification step to remove alkali metal contaminants, which would otherwise be required to avoid such contaminants detrimentally affecting the performance of the polymer material in many applications. Furthermore, the present inventors have found surprisingly that polymers prepared by this route have lower residual levels of palladium compared to polymers prepared by prior art processes. This is particularly important in the case that the polymer is to be used in a light-emitting device, since the presence of palladium is believed to have a detrimental effect on the optical performance of the device.

[0035] Furthermore, in the process of the present invention, the molecular weights grow gradually with time in these very controlled polymerisations. This has the advantage that repeatable (consistent) and desired molecular weights can be achieved by stopping the reaction at the appropriate stage.

Problems solved by technology

However, poly(arylene vinylene)s are not the only class of polymers which are suitable for use in optical devices.

However, such nonsolvents are acknowledged to slow down the rate of reaction.

Firstly, the reaction is very slow; reaction times are typically of the order of 12 hours in order to produce a polymer having a molecular weight of the desired order.

Discolouration of the polymer product and decomposition of the catalyst become concerns with such long reaction times. Secondly, the reproducibility of the reaction is somewhat poor.

These are difficult to remove, and the reaction thus requires the use of specialized reaction vessels.

The above problems also make this a very difficult and expensive process to scale up.

Images