Experimental and theoretical assignments of stereoregular poly(N-pentenylcarbazole) FT-IR spectra

The analysis of FT-IR spectra of isotactic and syndiotactic poly(N-pentenylcarbazole) (i-PPK and s-PPK) amorphous film samples are reported in the present paper. A comparison with FT-IR spectrum of a non stereoregular polyvinylcarbazole (PVK) commercial sample is also presented. Calculated vibration spectra of both i-PPK and s-PPK are obtained through the Density Functional Theory (DFT) method. Theoretical results are interpreted in terms of potential energy distribution (PED) analysis, and compared with i-PPK and s-PPK FT-IR experimental spectra. Only a few differences, due to the conformational constrain imposed by tacticity, are detected between the two fully amorphous polymer stereoisomers. Moreover, the observed differences between PPKs and PVK spectra are attributed to the presence of the alkylene linker (-(CH 2 ) 3 -) in PPK samples, distancing the carbazole groups to the main chain. The alkylene linker allows more flexibility to both the side and main chain of PPK samples, giving rise to new vibrational mixed modes which are not detected in PVK.