High-density liquid-crystalline azobenzene polymer brush attained by surface-initiated ring-opening metathesis polymerization.

High-density polynorbornene azobenzene liquid-crystalline brushes are synthesized on quartz substrates by surface-initiated ring-opening metathesis polymerization (SI-ROMP) using Grubbs third-generation catalyst. The grafting process is controlled over the thickness of the brush from a solid-supported substrate in a stoichiometric manner. A highly ordered liquid-crystal arrangement was formed for such brushes as revealed by spectroscopic measurements and grazing angle X-ray diffraction analysis. Marked features of this method in the structure and photoalignment behavior are unveiled by comparison with brushes made by surface-initiated atom-transfer radical polymerization (SI-ATRP).