Structure and optical activity of a crystalline modification of isotactic poly‐(S)‐4‐methyl‐1‐hexene

The results of an x‐ray and polarimetric study of a crystalline modification (form I) of isotactic poly‐(S)‐4‐methyl‐1‐hexene are reported and discussed. The x‐ray fiber spectra of this polymer are practically indistinguishable from those of isotactic poly‐(R)‐(S)‐4‐methyl‐1‐hexene. Although the crystal structure of the latter can be described on the basis of helices of different screw sense packed in a P4 space group, the crystal structure of poly‐(S)‐4‐methyl‐1‐hexene is better described on the basis of a P1 space group. The conclusion of the x‐ray investigation, that in the crystals of the optically active polymer an equal number of right‐handed and left‐handed helices must be present, is supported by the polarimetric measurements, which have shown that the polymer in the crystalline form I possesses a rather low rotatory power.