Photo-differential scanning calorimetry

The aim of this contribution is to highlight new applications of calorimetric techniques to study soft matter organization directly on this length scale. Two original techniques, namely thermoporosimetry (TPM) and photo-differential scanning calorimetry (photoDSC) will be presented from both the theoretical and experimental points of view. After giving the state of the art of the two techniques,... 

Photo Differential Scanning Calorimetry. A modified differential scanning calorimeter (Perkln-Elmer DSC 2C) was used to determine percent conversion for various Irradiation times. This was calculated from the residual polymerization energy remaining after sav jle Irradiation. 

An alkynyliodonium salt, namely, phenyl(phenylethynyl)iodonium hexafluorophosphate, has been tested for application as cationic photoinitiator [38]. The high activity of phenyl(phenylethynyl)iodonium salt as a photoinitiator was verified by photo differential scanning calorimetry (photo-DSC) experiments in direct irradiation and in photosensitized initiation using 9,10-dibutylanthracene, 2-isopropylthioxanthone and benzophenone as sensitizers [38]. 

The Photo-Differential Scanning Calorimetry (photo-DSC) [10] was used to study the cure kinetics of UV-initiated photo-polymerization of epoxy resin monomers and vinyl ether in presence of cationic photo-initiator, mainly Cyracure UVI-6976, former Cyracure UVI-6974, which consists of a mixture of dihexafluoroantimonate of S, S, S, S -tetraphenylthiobis (4,1-phenyllene) disulfonium and hexafluoroantimonate of diphenyl (4-phenylthiophenyl) sulfonium (CAS no. 89452-32-9 and 71449-78-0) at 50 wt. % in propylene carbonate - Figure 44 [11]. 

Thin PP film (30 pm, essentially unoriented, Hercules Profax resin, 55% crystalline by differential scanning calorimetry, DSC) were freed from processing additives by acetone extraction. Film was y-irradiated in a 60Co A.E.C.L. Gamma cell (0.14 or 1.35 Mrad.h-1 dose rate). Films were then analyzed immediately after irradiation or after a storage period either at room temperature or at 60°C in a forced air oven. For comparison purposes some extracted PP film was photo-oxidized in a xenon arc WeatherOmeter (Atlas 6500 watt, Pyrex inner and outer filters). 

The experimental procedure involves initiation of the polymerization by irradiation followed by cutting off the light after a certain time at a degree of conversion chosen, and monitoring the reaction in the dark. As experimental methods, both isothermal differential scanning calorimetry (photocalorimetry, photo-DSC) [2,6, 7, 18-32] and real-time infrared... 

The characterization methods applied to light-powered actuators encompasses a large array of techniques, most of which are common to viscoelastic materials, such as stress-strain curves, differential scanning calorimetry (DSC), and so on. For annealed films, the thickness with respect to the input information (light source) is measured by ellipsometry or neutron reflectivity, both of which are sensitive analytical tools for film thickness. The major analytical technique that differs from those already discussed in this chapter is UV-vis spectroscopy as it can be used to monitor the extent of photoisomerization. The different isomers give rise to different spectral absorption bands, which can be followed during the photo-illumination process. 

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