Single crystals of poly(tetramethylene adipate)

Single crystals of poly(tetramethylene adipate) (PTMA,-[O-(CH2)4-O-CO-(CH2)4-CO]n-) have been prepared by precipitation from solution and by epitaxial deposition on suitable substrates. The crystals grown from solution exhibited two distinct morphologies: most of the crystals were diamond-or truncated diamond-shaped, but a few were approximately hexagonal. These two morphologies yielded different diffraction patterns from which the polymorphic structures could be identified. Comparison of the electron diffraction patterns with the equatorial d spacings in the x-ray fiber diagrams indicated that the diamond and hexagonal morphologies correspond to β-and α-PTMA, respectively. The growth faces are the 110 planes for the β single crystals and both the 010 and 110 planes for the α single crystals. Epitaxial crystals were produced by deposition from the melt on trioxane and both from the melt and from solution on potassium halide crystals. The electron diffraction patterns of these crystals indicate that the PTMA chains are oriented parallel to the substrate surface. The crystals grown from the melt on potassium iodide are identified as the β-form and the layer line spacing is determined to be 14.67 Å, which defines the chain conformation as planar zigzag. In the same manner, the crystals grown from the melt on trioxane are identified as α-PTMA.