X-ray Diffraction by Liquid-Crystalline Polymers

Following a brief introduction to how acicular molecules form liquid-crystalline (LC) arrays in polymers, relevant elements of x-ray diffraction theory are discussed. It is shown that meaningful structural information can be obtained only when molecular arrays aligned by external forces are examined, a condition that is frequently easier to achieve in polymer than in monomer arrays. The published results of x-ray studies are reviewed critically and the interpretations of recorded intensity distributions are discussed in terms of model calculations and cylindrical distribution functions. Examples cited include side-group and main-chain LC homopolymers and main-chain copolymers.