Title

Copolymerlike Structures of Nematic Nitroimine Dimers

Document Type

Article

Publication Date

1990

Department

Chemistry and Biochemistry

Abstract

X-ray diffraction diagrams of a homologous series of nitroimine dimers were recorded at their nematic temperatures in a magnetic field of 2,000 G. Two kinds of well aligned monodomains could be distinguished. When the central aliphatic chain contained an even number of methylene groups, the degree of alignment was higher than when n was odd. The aperiodic spacing of up to eight meridional maxima suggested that the dimers form aperiodic linear arrays containing two recurring repeat distances whose lengths were determined by point-model calculations to approximate extended coupled dimers having singly and doubly overlapping phenyl rings, respectively. Line-model calculations based on complete intensity profiles showed that the double overlap was favored when n is even and increases with increasing length of the central spacer chain.

Publication Title

ACS Symposium Series

Volume

435

First Page

268

Last Page

278