ISSN:
0323-7648
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
X-ray diffraction has been used to determine the structure of the poly(p-phenylene 2,5-di-hexadecyloxy-terephthalate), which is one of a series of polyesters with stiff aromatic mainchains and flexible aliphatic sidechains currently being studied by this laboratory. The X-ray data for oriented melt quenched films show that this polymer adopts an interesting and novel structure, in which the backbones and sidechains form separate incommensurate lattices. The backbones are fully extended, and adopt a monoclinic structure with unit cell dimensions: a=26.2Å, b=7.3Å, c=12.6Å, and α=130°C. They are in contact along the b axis, thereby forming stable sheets that are separated by intercalated, highly extended sidechains, which point along the a axis. The sidechains are packed in a columnar, approximately hexagonal structure that is similar to the hexagonal form of linear alkanes. The repeat for the sidechain lattice along the backbone direction is c=13.2Å, and thus the two lattices are incommensurate. We envisage a small disordered boundary layer between the backbone and sidechain lattices, containing some of the inital and final carbons of the sidechain, and accommodating any conformational isomerism. This allows an independent lattice to be formed by the central sections of the sidechains, but this cannot propagate indefinitely because of the different c dimension and the restrictions imposed by covalent linkage to the backbones. As a result, the sidechain crystallites are only approximately 50Å wide, compared to approximately 200Å for those formed by the backbones. Simulated X-ray patterns for the above incommensurate structure show good qualitative agreement with the observed data.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/actp.1994.010450308
Permalink
