Examples Using Rapid Scan FTIR Spectroscopy

4 Examples Using Rapid Scan FTIR Spectroscopy 

An IR technique can obtain spectra every 5-10 seconds of a reacting PU foam system having a given temperature profile (360). The real-time IR spectroscopy method was found to be particularly useful for analysing high conversion kinetics. Results were obtained also for poly(ethylene glycol 200) dimethacrylate and poly(ethylene glycol 600) dimethacrylate (263). 

FTIR spectroscopy was applied to the study of polymerisation kinetics of simultaneous interpenetrating polymer networks composed of PU and vinyl ester resin (238). The comparison of vinyl ester resin with or without its pendant hydroxyl groups was also made to examine the intercomponent chemical binding effect. 

The copolymerisation of A-cyclohexylmaleimide (CHMI) and methyl methacrylate (MMA) using azobisisobutyronitrile as the initiator using rapid scan IR. Using the Mayo-Lewis equation, the reactivity ratios of CHMI and MMA were calculated (64). 

By measuring the presence of functional groups at finite depths from the crystal surface by real time ATR-FTIR spectroscopy, the conversion during acrylate polymerisations was measured. By varying the film thickness, the reactivity of multiacrylates could be spatially resolved (262). The simultaneous monitoring of vinyl acetate (VA) and erucamide additive concentrations in EVA copolymers was undertaken with NIR spectroscopy using an in-line flow cell attached to an extruder (130). 

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The challenge now is to perform time-resolved experiments and thus, to benefit from the huge potentialities of infrared spectroscopy to identify reaction mechanisms induced by irradiation. For example, in the LINAC-FTIR coupling, the Rapid Scan system of the spectrometer can be used with a resolution of 100 to 10 ms, and for reactions much faster it could be possible to use the Step Scan system. 

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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