Synthesis and properties of poly (diphenylacetylenes) having aliphatic para‐substituents

Abstract 1‐( p‐t ‐Butylphenyl)‐2‐phenylacetylene and 1‐( p‐n ‐butylphenyl)‐2‐phenylacetylene were polymerized in catalytic systems based on TaCl 5 to give new polymers in high yields. These monomers were more reactive than diphenylacetylene (DPA) in copolymerization. Unlike poly (DPA), the present polymers were soluble in toluene, CHCl 3 , etc. owing to the high configurational entropy induced by the para ‐substituents. Their relative weight‐average molecular weights determined by GPC were in the range of 6 × 10 5 –36 × 10 5 , and films could be obtained by solution casting. These polymers were fairly thermally stable, as seen from their high onset temperatures (320–380°C) of weight loss in TGA in air. The oxygen permeability coefficient of the polymer with t ‐Bu group was 1100 barrers, the highest among those of all the hydrocarbon polymers.