CROWNED POLYACETYLENE .2. CIS FORM DETERMINATION OF POLY(4'-ETHYNYLBENZO-15-CROWN-5) BY SOLID-STATE NMR METHOD

The chain structure of cis-poly(4'-ethynylbenzo-15-crown-5) (PEB15C5), prepared using the rhodium complex catalyst, was studied at -175 degr ees C using the solid-state NMR technique. The second moment of PEB15C 5 was 7.0 G(2) for the main chain and 19.0 G(2) for the side chain. Th ese values agreed well with the respective theoretical ones for the ci s form in the rigid state rather than the traits one. This agreement b etween experiment and theory suggested that the plane of the side chai n (i.e., the benzo-15-crown-5 group) is orthogonal to the main chain p lane of the cis-transoidal form. It was verified that the strong dipol e-dipole interaction between the side chains plays an important role a s a clue to theoretically determine the cis-transoidal form. NMR resul ts in solid state confirmed theoretically that multipeaks in the H-1 a nd C-13 NMR spectra in CDCl3 solution are attributed to cis-transoidal form in the chain. (C) 1995 John Wiley & Sons, Inc.