Unusual Thermal Polymerization of 1,4-Bis-5-(4,4‘-dialkyl-2,2‘-bithiazolyl)-1,3-butadiynes: Soluble Polymers from Diacetylenes

The syntheses of the 1,4-bis-5-(4,4‘-dialkyl-2,2‘-bithiazole)-1,3-butadiynes, ABD s, ( 6a − c ) are reported. The crystal and molecular structure of the butyl derivative was determined by single-crystal X-ray diffraction. The BBD (the 4,4‘-di- n -butyl ABD ) molecules are properly aligned in the solid state for topotactic 1,4-polymerization to occur, but these materials do not undergo such polymerization under a variety of conditions. The lack of topotactic polymerization is attributed to the rigidity of the aromatic groups directly bonded to the butadiyne. These compounds do polymerize in the molten state to give soluble polymers that are characterized by UV−vis, FT-IR, and NMR spectroscopies and cyclic voltammetry. Molecular modeling was also used to explore some representative conformation space. These data suggest that the polymerization occurs primarily via 1,2-addition, but some 1,4-addition also occurs.