Tensile properties and partial alignment of polyacetylene, (CH)x,films

The tensile properties of both cis- and trans-polyacetylene, (CH)_x, were investigated in order to determine the variables that influence that ultimate extension ratio (l/l₀) of polyacetylene films. It was found that when cis-films of polyacetylene were extended in an inert (argon) atmosphere, ultimate extension ratios as high as 3.3 were obtained and with subsequent isomerization at 160–200°C under stress, a final l/l₀, of about 4 was obtained. The extension ratio is extremely sensitive to exposure to oxygen and decreases markedly after periods as short as 1 min. It appears as though crosslinking may occur in the polymer when it is exposed to air and this produces brittleness in the specimen. When (CH)_x was isomerized from cis to trans, it became brittle, even in the absence of air.