Variable Temperature Measurements and Hydrogen Bonding

Spectroscopic studies at variable temperatures have become an important tool for the characterization of the physical structure of polymers. Especially in combination with thermoanalytical DTA or DSC measurements short-time spectroscopic FTIR investigations in controlled heating or cooling experiments provide a detailed picture of the structural changes as a function of temperature. Any variations of spectroscopic parameters such as intensity, wavenumber position and band shape directly reflect the temperature dependence of the vibrational behaviour of the investigated polymer as a consequence of changes in the inter- and intramolecular interactions and the state of order The vibrational spectra of polymers recorded in selected 

The role played by hydrogen bonds in the structure and properties of polymeric solids has been the subject of numerous investigations As far as the 

Hydrogen bonding involves the interaction between a proton donating group (Ri—X—H) and a proton acceptor (Y—R2) and may be described sdiematically by 

The formation of a hydrogen bond is generally favoured by highly electronegative X and Y atoms with relatively small atomic radii (for example, O, N, F) and requires Y atoms with loiK-pair electrons .  

As a consequence of the hydrogen bonding forces the v(XH) and v(YR2) stretching frequencies win be lowered, whereas the ddformation frequencies associated with the motions of the H and Y atoms perpendicular to their X—H and Y—R2 bonds, respectively, wiH be iiKxeased. 

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