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Ab initio studies on polymers. VII. Polyoxymethylene

✍ Scribed by Alfred Karpfen; Anton Beyer

Publisher
John Wiley and Sons
Year
1984
Tongue
English
Weight
490 KB
Volume
5
Category
Article
ISSN
0192-8651

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✦ Synopsis

The structure of an isolated, infinite polyoxymethylene chain has been investigated with the aid of the ab initio crystal orbital method applying a basis set of double-zeta quality. Restricting the primitive unit cell to a single CH2O group, conformational potential curves as a function of the torsional angle have been evaluated. Only a single minimum closely corresponding to an all-gauche structure was detected. The all-trans conformation is a maximum on the energy curve for simultaneous rotation around C-0 single bonds. Detailed geometry optimization in the vicinity of the all-gauche conformation led to the following structure: rco = roc = 1.425 21, rcH = 1.072 A, LHCH = 111.7', LOCO = 110.9', LCOC = 115.1', and TOCOC = 70.75'. The computed torsional angle TOCOC lies midway between the hexagonal (78.2') and the orthorhombic (63.5') modification of solid polyoxymethylene.

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