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We describe a novel thermal characterization technique based on a differential arrangement, which achieves spatially localized calorimetric analysis. It involves the use of an active probe which acts both as a highly localized heat source and a thermometer. This ability opens the way for the implementation of scanning calorimetric microscopy where image contrast will be created from thermal analysis data. For a number of polymers we have recorded events such as glass transitions, meltings, recrystallizations and thermal decomposition within volumes of material estimated at a few μm3. The data obtained are compared with those obtained from conventional calorimetry and the events registered in both cases are found to match. For a full quantitative analysis of the results obtained, mathematical modelling of the operation of the technique, taking account of physical and other changes in materials, is required.

We have used a miniaturized Wollaston wire resistive thermometer as a probe to record infrared absorption spectra of polymeric samples by detecting photothermally induced temperature fluctuations at the sample surface. This method opens the way to absorption Fourier transform infrared spectroscopy/microscopy with a spatial resolution that is no longer diffraction limited, but is determined instead by the size of the contact between probe and sample. At present, this is on the order of a few hundred nanometers. The thermal probe, of a type used in scanning thermal microscopy and microthermal analysis, allows us to detect the photothermal response of a specimen exposed to the beam of a Fourier transform infrared spectrometer and heated thereby. The signal from this probe measures the resulting temperature fluctuations, and thus provides an interferogram which replaces the interferogram normally obtained by means of direct detection of the IR transmitted by a sample.