The full vibrational spectra of
![](/images/gifchars/alpha.gif)
and
![](/images/gifchars/beta2.gif)
crystalline phases of syndiotactic polystyrene (sPS), that is, phasespresenting the trans-planar conformation, have been experimentally determined and compared with thatcalculated at the B3LYP/6-31G(d,p) level of theory for an infinite trans-planar chain. The normal vibrationalanalysis of most representative modes of the periodic model allowed us to give a general description of eachone, which was further confirmed by the direct inspection of mode animations. An assignment of the differentmodes was performed in terms of frequency, relative intensity, and direction of the transition-moment vectorof the observed IR peaks as well as Raman vibrational frequencies.