Liquid crystal photoalignment properties of polymethylphenylsilane

Polymethylphenylsilane (PMPS), prototype of polysilanes, is considered as p hotoaligning material for liquid crystals (LC). The LC photoalignment on PM PS is characterized by the singular low exposure energy (E less than or equ al to 50 mJ) necessary to produce LC alignment. Dependence of the azimuthal anchoring energy W-a an the exposure time tau(exp) is non-monotonous; curv e W(tau(exp)) sharply increases, goes through a maximum and decreases to th e values close to zero. The easy axis of LC alignment is induced in the dir ection of light polarization. Possible microscopic mechanisms of LC photoal ignment on PMPS layers are discussed. (C) 2000 Elsevier Science B.V. All ri ghts reserved.