| Polyphenylacetylenes have been considered one of the focuses of research in the area of conducting polymers. So far only head-tail polyphenylacetylenes have been studied because traditional polymerization methods only produce them. In this project a new type of polyphenylacetylenes, the head-head polyphenylacetylenes, has been synthesized by the rearrangement of a group of precursor polymers. Unlike head-tail polyphenylacetylene, head-head polyphenylacetylene can adopt all trans, planar conformation. UV/vis absorption peaks shift from 250nm for head-tail polyphenylacetylene to 460nm for head-head polyphenylacetylene, corresponding to extending the effective conjugation length from 2–3 to 10.5. By adding methyl substituents to the ortho position on the phenyl rings, the steric effect cause the phenyl rings to rotate away from positions parallel to the backbone, allowing better conjugation on the backbone. The UV/vis absorption peak for head-head poly(o-methylphenylacetylene) shifts to 500nm, corresponding to effective conjugation length of 13.5.; In addition, a new type of Pd(P-P) catalyst has been successfully applied to the polymerization of phenylacetylene. The head-tail polyphenylacetylene produced also served as a reference sample for head-head polyphenylacetylene. |
