Influence of conformational structure on the vibrational spectra of the different isomers of 2,4,6,8-tetraphenylnonane,a polystyrene model molecule

The influence of the chain configurations and conformations on the infrared and Raman spectra of 2,4,6,8-tetraphenylnonane has been investigated. The out-of-plane, skeletal, 16b and 10b normal modes of the benzene rings, and the methyl rocking are particularly sensitive to conformational effect. The results permit evaluation of the trans-trans defect ratio in isotactic crystalline polystyrene and suggest that atactic polystyrene is better described by prevailing syndiotactic sequences of at least eight aliphatic bonds in the trans conformation.