Junichiro Washiyama

Crystal structures of α and β forms of poly(tetramethylene succinate)

Abstract Crystal structures of the α and β modifications of poly(tetramethylene succinate) (PTMS) were analyzed by X-ray diffraction: the β form appeared with an application of stress. These two modifications belonged to the monoclinic system with the space group of P21/n. In both cases, a unit cell included two chemical repeating units. For the α form, the cell dimensions were a=0.523 nm , b=0.912 nm , c (fiber axis) =1.090 nm , and β=123.9°; for the β form, a=0.584 nm , b=0.832 nm , c (fiber axis) =1.186 nm , and β=131.6°. The difference in the fiber periods of the two crystalline forms was attributed mainly to the conformational difference in the tetramethylene unit, i.e. TGT G T of the α form and TTTTT of the β form. It was also found that in PTMS, the packing coefficient, K, which was defined by the ratio of the intrinsic volume with respect to the true volume of the α form was almost equal to that of the β form. This observation could be contrasted to those obtained in poly(butylene terephthalate) (PBT), where the K of the α form was considerably greater than that of the β form. The difference between PTMS and PBT was attributed to the difference between the unit cell volumes of the α and β forms of these polymers.

Strain-induced crystal modification in poly(tetramethylene succinate)

Abstract A new crystal modification induced by strain was found in uniaxially oriented fibres of poly(tetramethylene succinate). This new modification (β form) had a planar zigzag conformation of T10 (all trans) and a fibre identity period of 11.90 A, while the conventional α form had a T7GTḠ conformation and fibre identity period of 10.90 A. The solid-state crystal transition between α and β forms was reversible with respect to the successive application and release of strain.

1,6,11,16-Tetraoxacycloeicosane-2,5,12,15-tetraone.

The 20-membered ring of the title compound, C 16 H 24 O 8 , adopts an approximately flat rectangular structure with three-and seven-bond sides and lies across a crystallographic center of inversion. The corners of the ring occur at both ends of one of the planar ester segments. All of the carbonyl O atoms are involved in intermolecular C-H···O hydrogen bonds.