An evidence has been found by 1H and 13C NMR techniques for the presence of structural isomerism of side chain in liquid crystalline polysiloxane due to α- and β-additions of alke-ne monomers. A liquid crystalline polysiloxane from poly (methylhydrosiloxane) and 4-(al-lyloxy) benzoyl-4-methoxyphenyl contains as many as 42% α-addition isomeric side chains based on our NMR data. It is thus pointed out that the strength change of Si-H absorption band in IR or NMR spectra can only reflect the extent of completion of hydrosilation

it does not necessarily mean the liquid crystalline polysiloxane produced contains β-addition iso-meric side chains only.