Photogeneration of conducting polymer patterns in iodinated cis-1,4-polybutadiene films

Abstract

We have previously demonstrated that ‘I 2-doping’ of certain 1,4-polydiene chains led to polar addition of I 2 into the isolated double bonds, followed by HI elimination resulting in the formation of conjugated sequences of unsaturated double bonds in the polymer backbone. In particular, the ‘doping’ of trans-1,4-polybutadiene with iodine has been shown to generate conjugated semiconducting polymer at room temperature, but an analogous treatment on cis-1,4-polybutadiene did not lead to the formation of conjugated sequences due to an unfavorable combination of electronic and steric interactions associated with the cis-isomer which inhibits the E-2 elimination of HI at room temperature. Using a cis-1,4-polybutadiene film as the starting material, however, we have prepared conducting patterns in the polymer matrix through a microlithographically patterned cis– trans isomerization, followed by a region-specific ‘I 2-doping’ of the photoisomerized trans-1,4-polybutadiene chains in the UV exposed regions. In our further investigation on the photochemical generation of conducting patterns in polybutadiene films, we found that photo-irradiation of the iodinated cis-1,4-polybutadiene can lead to the HI elimination and hence the formation of conjugated sequences. Based on this finding, we have recently developed a single-step photolithographic method for generating conducting micropatterns in the iodinated cis-1,4-polybutadiene film through a patternwise photo-elimination of HI. Unlike our previously reported photo-patterning technique, the newly developed method completely eliminates those steps associated with the patterned photo-isomerization and development by selective ‘I 2-doping’. Therefore, the dramatically simplified one-step microlithographic method to be reported in this paper represents a significant advance in generating conducting patterns in polydiene rubber films for optoelectronic applications.