The IR spectra of solutions of a perfluorinated polyamide in different solvents are analyzed in the spectral range of “free NH” stretching modes, in order to study the effects of hydrogen bonding in determining the unusual spectral behaviour observed for these systems. The presence of different bands in the spectral range associated to NH bonds with the H atom not involved in hydrogen bonding and their evolution with the polymer concentration has shown that free NH bonds have a different nature depending on the occurrence of hydrogen bonding on neighbour atoms and on the configuration of the molecular complexes in which they are involved. These differences have been interpreted on the basis of DFT (B3LYP/6-311++G**) computations on suitable molecular models that allowed a qualitative and quantitative rationalization of the chemical–physical effects involved. The computational analysis points out the subtle intramolecular and intermolecular vibrational effects occurring in these systems and brings to an interpretation and assignment of the IR spectra which goes over the interpretations usually adopted when dealing with the vibrational spectroscopy of hydrogen bonded polymers and molecules.

Hydrogen bonding effects in perfluorinated polyamides: an investigation based on infrared spectroscopy and density functional theory calculations

MILANI, ALBERTO;CASTIGLIONI, CHIARA;
2010

Abstract

The IR spectra of solutions of a perfluorinated polyamide in different solvents are analyzed in the spectral range of “free NH” stretching modes, in order to study the effects of hydrogen bonding in determining the unusual spectral behaviour observed for these systems. The presence of different bands in the spectral range associated to NH bonds with the H atom not involved in hydrogen bonding and their evolution with the polymer concentration has shown that free NH bonds have a different nature depending on the occurrence of hydrogen bonding on neighbour atoms and on the configuration of the molecular complexes in which they are involved. These differences have been interpreted on the basis of DFT (B3LYP/6-311++G**) computations on suitable molecular models that allowed a qualitative and quantitative rationalization of the chemical–physical effects involved. The computational analysis points out the subtle intramolecular and intermolecular vibrational effects occurring in these systems and brings to an interpretation and assignment of the IR spectra which goes over the interpretations usually adopted when dealing with the vibrational spectroscopy of hydrogen bonded polymers and molecules.
Hydrogen bonding; Fluorinated polymers; Vibrational spectroscopy
File in questo prodotto:
File Dimensione Formato  
ammidi_polymer_final.pdf

Accesso riservato

: Post-Print (DRAFT o Author’s Accepted Manuscript-AAM)
Dimensione 2.48 MB
Formato Adobe PDF
2.48 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11311/571965
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 19
  • ???jsp.display-item.citation.isi??? 20
social impact