Crystal Structures of Isotactic and Atactic Poly(1-pentamethylene alcohol)

Wehave determined the crystal structures of highly regioregular(>97% HT additions) isotactic- and atactic-poly(1-pentamethylenealcohol)s(PPMA, -[(CH2)(4)CH(OH)]( n )-) by a quantitative analysis of 2-dimensional wide-angleX-ray diffraction data. The unit cell houses two chains in a planar-zigzagconformation, with orthorhombic symmetry and parameters a = 8.637 & ANGS;, b = 4.987 & ANGS; and c (chain axis) = 12.840 & ANGS; for the it-PPMA and a = 8.76 & ANGS;, b = 5.06 & ANGS;, and c (chain axis) = 12.840 & ANGS; for the at-PPMA. The space group is P2(1)2(1)2(1) for both polymers.The zigzag planes are nearly parallel to the rolled plane of the doublyoriented sample. These regularly packed chains are aggregated in twinneddomains having two opposite orientations of the unit cells. In thecase of at-PPMA, the random stereochemical positioning of the alcoholpendants results in a more expanded unit cell than the correspondingcell of it-PPMA. Intermolecular hydrogen bonds form along the b axis for both the it- and at-species, the strength ofwhich is slightly different depending on the OH configuration, asjudged from infrared spectral information as well as the O & BULL;& BULL;& BULL;Ointermolecular distances.