Crystal Structures of Isotactic and Atactic Poly(1-pentamethylene alcohol)
Kohji Tashiro, Gina A. Guillory, Stephanie F. Marxsen, Justin G. Kennemur, Rufina G. Alamo
Abstract
We have determined the crystal structures of highly regioregular (>97% HT additions) isotactic- and atactic-poly(1-pentamethylene alcohol)s (PPMA, −[(CH 2 ) 4 CH(OH)] n −) by a quantitative analysis of 2-dimensional wide-angle X-ray diffraction data. The unit cell houses two chains in a planar-zigzag conformation, with orthorhombic symmetry and parameters a = 8.637 Å, b = 4.987 Å and c (chain axis) = 12.840 Å for the it-PPMA and a = 8.76 Å, b = 5.06 Å, and c (chain axis) = 12.840 Å for the at-PPMA. The space group is P 2 1 2 1 2 1 for both polymers. The zigzag planes are nearly parallel to the rolled plane of the doubly oriented sample. These regularly packed chains are aggregated in twinned domains having two opposite orientations of the unit cells. In the case of at-PPMA, the random stereochemical positioning of the alcohol pendants results in a more expanded unit cell than the corresponding cell of it-PPMA. Intermolecular hydrogen bonds form along the b axis for both the it- and at-species, the strength of which is slightly different depending on the OH configuration, as judged from infrared spectral information as well as the O···O intermolecular distances.