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Establishing the Thermal Phase Behavior and its Influence on Optoelectronic Properties of Semiconducting Polymers
Published in John R. Reynolds, Barry C. Thompson, Terje A. Skotheim, Conjugated Polymers, 2019
Beside the crystallization and melting temperature, the glass transition temperature, Tg, is highly relevant when applying polymer semiconductors in devices.36 A number of structural parameters affect the glass transition temperature, which is the temperature below which segmental relaxations are suppressed. The empirical Flory–Fox equation1,46,47 describes, for example, the increase in Tg with molecular weight, M: Tg(M) = Tg(M∞) – K/M, where Tg (M∞) is the glass transition temperature of a polymer with infinite molecular weight (infinite chain length) and K is a polymer-specific constant.46,47 This equation implies that, very similar to the dependence of the melting temperature on molecular weight, for shorter macromolecules (low-molecular weight materials), the Tg first increases with molecular weight before reaching a plateau value for longer-chain polymers (higher-molecular weight materials) where Tg is essentially independent of chain length.
Preparation and characterization of polysulfone-polyurethane membranes for recovery of simulated wastewater from industrial textile processes
Published in Environmental Technology, 2022
N. J. Bogoni, C. R. Schut, J. Z. Merck, J. Duarte, C. M. Menezes, M. Giovanela, M. A. Zeni, C. Marangoni, J. S. Crespo
Thermal analysis of pure PU (see Support Material) shows two glass transition temperatures. The first one, around −19°C, is related to soft segments (usually a polyether or polyester polyol) while the second one, around 30°C, is related to hard segments (chain extender) [50]. The melting temperature (Tm) of the PU used in this work range from 47°C to 55°C, while for PSf, the glass transition temperature is around 187°C. Using the results of thermal analyses, the glass transition temperature of the polymer blend was calculated from the Flory-Fox equation (Equation 5): where Tg, Tg1 and Tg2 are glass transitions of the blend, component 1 and component 2 respectively, W1 and W2 are the weight fractions of the respective components. The Tg value obtained for the polymer blend was 47°C, which can also be seen in the DSC results shown in Figure 5. M0 displays a band that covers a wide temperature range (from 47°C to 55°C) indicating the overlap of Tg and Tm as shown in Figure 5(a). Unlike the others, M1 and M2 membranes (Figure 5(b)) exhibit well-defined Tg and Tm, with results that corroborate the calculated Tg, indicating the miscibility of the polymers as well as their melting temperature, which is around 53°C.
Experimental and computational evaluation of the degree of micro-collapse formations in freeze-dried cakes
Published in Drying Technology, 2023
Kyuya Nakagawa, Daiki Morishita, Tetsuo Suzuki, Noriaki Sano
This equation yields the of a matrix at a specific moisture content in combination with the glass transition temperatures of the pure substances (i.e., water and dextrin). The values of pure dextrins were estimated using the Flory–Fox equation by applying the mean molecular mass () of the dextrins.[37]