A New Electron-withdrawing Group Containing Poly(1,4-phenylenevinylene)

We have synthesized and investigated the electronic properties of poly[2-(2‘-ethylhexyloxy)-5-phenyl-1,4-phenylenevinylene], <BO>12</BO>, and its methylsulfonyl derivative poly[2-(2‘-ethylhexyloxy)-5-(4‘ ‘-methylsulfonylphenyl)-1,4-phenylenevinylene], <BO>13</BO>. Polymer <BO>13</BO> contains a second-order nonlinear optic chromophore which is in conjugation with the polymer backbone. Polymers <BO>12</BO> and <BO>13</BO> have been used as the electroluminescent (EL) layers in single layer light-emitting diodes (LEDs) (ITO/polymer/Al). We have found that when <BO>12</BO> was used, the LEDs had an external EL quantum efficiency of 0.01%. Attachment of the methylsulfonyl moiety to <BO>12</BO> to give <BO>13</BO> in an attempt to increase the electron affinity of the parent polymer was found to make no difference to the efficiency of the single layer EL devices and appeared qualitatively to reduce their lifetimes.