Rheooptical FTIR Spectroscopy

The molecular orientation of the epoxy networks was investigated using rheooptical FTIR spectroscopy and uniaxial deformation was carried out above and below the Tg. The effects of diol chain length and molar ratio on the mechanical properties and orientation parameter were discussed (79). 

For PS/poly(vinyl methyl ether) blends, the addition of poly(vinyl methyl ether) to the blend increases the orientation of the PS chains during the stretching (92). 

Phase-locked electronics are used to record the dynamic IR spectral change in-phase and out of phase with the applied mechanical field. The method provides insight to the response to the external stress on the molecular and submolecular scale. Rheooptical FTIR spectroscopy is one of the few techniques providing data on the crystallisation, orientation and conformational changes of a polymer during mechanical treatment (83). Two dimensional correlation analysis is utilised to enhance the information derived from the vibrational spectroscopic data. 

The IR rheooptical technique was applied to study the molecular processes that take place along the stress-strain curve of PET yams. The results indicate that the first modulus maximum marks the breakdown of the amorphous entanglement network and the start of molecular uncoiling by gauche-to-trans transitions. In addition, stress develops on the crystals and particularly on tie molecules with a short contour length in the amorphous domains. Ultimately, molecular fracture of taut-tie molecules (extended chains of polymers between crystals) causes the modulus to pass through a second 

Rheooptical FTIR spectra of a thermoplastic polyester urethane and Nylon 6 films were recorded under a varying sinusoidal strain. The large bipolar bands in the dichroic in-phase spectra, caused by large frequency shifts of the original monopolar absorption bands, were ascribed to hydrogen bonds (102). 

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Some new developments of two-dimensional spectroscopy are discussed. As a specific example, two-dimensional correlation analysis of a polymer laminate film using several different spectroscopic techniques is presented. The versatility of this technique was developed using depth-profiling photoacoustic spectroscopy, mid-and near-IR dynamic rheooptical developments, and spectroscopic imaging microscopy. Spatial and temporal variations of near-IR spectra are effectively analysed by the two-dimensional correlation technique. Step-scanning FTIR spectrometers provide an opportunity to obtain desired spectral information often difficult to obtain by the conventional rapid-scanning technique. 12 refs. 

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