Some observations on the structure of Durham polyacetylene

The structure of polyacetylene produced from a precursor polymer is compared with that of polymer produced by a soluble Ziegler-Natta catalyst. X-ray diffraction shows that the precursor polyacetylene can be produced with a wide range of ordering from apparently amorphous to crystalline, although the ordering is never as high as that of polymer produced by the Ziegler-Natta route. An increase in ordering, as measured by X-ray peak width, has been observed during isomerization; this contrasts with normal polyacetylene where no change in order is found. Both forms of polyacetylene show a gradual shift in the interchain d -spacing from 395 pm ( cis/trans mixed) to 365 pm ( trans ). Since only a single peak is found in this region the cis - and trans -forms are not phase-separated on a scale of 3 nm or more. Small-angle X-ray scattering also indicates that discrete crystalline and amorphous regions, as found in polyethylene, are not present