Blend time measurement data analysis

Recent developments have been in the area of microthermal analysis using thermal conductivity with thermal diffiisivity signals or AFM to visualize specific areas or domains in the material and perform localized thermal analysis studies (183,184). Relaxational behavior over time and temperature is related to changes in free volume of the material. Positron annihilation lifetime spectroscopy (PALS) measurements of positron lifetimes and intensities are used to estimate both hole sizes and free volume within primarily amorphous phases of polymers. These data are used in measurement of thermal transitions (185,186) structural relaxation including molecular motions (187-189), and effects of additives (190), molecular weight variation (191), and degree of crystallinity (192). It has been used in combination with DSC to analyze the range of miscibility of polymethyl methacrylate poly(ethylene oxide) blends (193). 

Because Qcoii is a direct measure of the charge present in the layer at a delay time fd, the recombination dynamics can be determined via an iterative procedure [171]. For the data shown in Fig. 20, this analysis yields y = 3.5xl0 m s and y= 1.2 X 10 m s for the chloroform as-cast and the annealed P3HT PCBM layer, respectively. The value for the annealed sample agrees very well with the bimolecular recombination coefficient measured by TAS at carrier densities typical for steady-state AMI.5 illumination (see, e.g., [189, 195]). To compare these values to the Langevin limit, the mobilities of the electrons and the holes in the blend must be known. Information on these quantities can be gained from drift-diffusion simulations of the photocurrent transients with different collection biases (see Fig. 20b). This yields mobilities of 1.2 x 10" m and... 

Dynamic mechanical analysis is an extremely powerful and widely used analytical tool, especially in research laboratories. In addition to measuring the temperature of the glass transition, it can be used to study the curing behavior of thermosetting polymers and to measure secondary transitions and damping peaks. These peaks can be related to phenomena such as the motion of side groups, effects related to crystal size, and different facets of multiphase systems such as miscibility of polymer blends and adhesion between components of a composite material [24]. Details of data interpretation are available in standard texts [1,2,25]. In the next section, we consider time-temperature superposition, which is another very useful apphcation of dynamic mechanical data. 

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