Polyamides with piperazine units in the polymer chain—I: Crystal structure and molecular packing of poly(1,4 piperazine-trans-4-octen-1,8 dioyl)

The crystal structure of poly(1–4 piperazine-trans-4-octen-1,8 dioyl) has been determined from X-ray fibre spectra. The unit cell parameters are: $\text{α=4.54 A; b = 10.00}\text{A}\text{?}\text{; c =13.50}\text{A}\text{?}$ (fibre axis) β = 110°15′ space group P2₁/n. Z =2, d_x = 1.28 g/cm³ (d_obs = 1.23 g/cm³).The chain symmetry is ti. The value of β ≠ 90° is determined by the necessity of suitably packing the neighbouring paraffinic chains and piperazine rings, at the shortest possible distance. The mode of packing of the paraffinic portions of the chains, in the a direction, is reminiscent of the analogous situation met for polyalkenamers (even series).