The structures and properties of epoxycyclohexyl POSS, glycidyl POSS, and diglycidyl ether of bisphenol-A.
(a) The plots of dH/dT for the epoxycyclohexyl POSS-DGEBA mixtures against the temperature. The composition is in wt. % (x g of epoxycyclohexyl POSS in (100 - x) g of DGEBA). The cooling and heating rates were 10 K/min. The intersecting straight lines indicate how T g was obtained. (b) The corresponding plots of the normalized C p against the temperature. The continuous line is the fit of the TNM-formalism and the dots are the measured data. T g is marked by the arrows. (Cyclohexyl POSS refers to epoxycyclohexyl POSS.)
The plots of dH/dT for the glycidyl POSS-DGEBA mixtures against the temperature. The composition is in mol % (x mole of glycidyl POSS in (100 - x) mole of DGEBA). The cooling and heating rates were 10 K/min. The DSC instrument could not maintain a cooling rate of 10 K/min at T < 213 K. It reduced to ∼2 K/min by the time the temperature was 183 K.
The plots of the normalized C p for the glycidyl POSS-DGEBA mixtures obtained from the plots in Fig. 3 . The composition is in mol. %. The continuous line is the fit of the TNM-formalism and the dots are the measured data. T g is marked by the arrows.
(a) The values of β cal for the epoxycyclohexyl POSS-DGEBA and glycidyl POSS-DGEBA mixtures are plotted against the composition. For epoxycyclohexyl POSS-DGEBA, x is in wt. % (x g of glycidyl POSS in (100-x) g of DGEBA), and for glycidyl POSS-DGEBA, x is in mol. %. (b) The values of β cal of different liquids plotted against the mol. % composition. The data are taken from the literature and β cal is an average over the glass-softening range in all cases, as described in the text.
(a) The plots of normalized C p of the liquid and plastic crystal state of ethanol against the temperature. The cooling rates for the liquid and of the orientationally disordered crystal were 0.08 K/min and the heating rates were 1.3 K/min. The data are for unannealed samples taken from Ref. 109 . (Data used with permission, copyright 2011 Wiley, VCH.) (b) The plots of normalized C p of 1-butanol and 2-butanol against the temperature. The cooling rate was 0.2 K/min for both isomers and the heating rate was 1.2 K/min for 1-butanol and 1 K/min for 2-butanol. The C p values were read from Fig. 1 in Ref. 111 . (Data used with permission, copyright 2011, Wiley VCH.) (c) The plots of measured C p of bulk polystyrene and its 17 nm thick film against the temperature. The data were read from Fig. 2 in Ref. 112 . (Data used with permission, copyright 2006, Wiley Periodicals.) The measured C p of the 17 nm thick film is 0.09 J/(g K) less than that of the bulk sample. SCL refers to supercooled liquid and ODC to the orientationally-disordered crystal.
An illustration for the change in the normalized relaxation function and the strength of relaxation processes with temperature. On cooling, the curves shift to the right (longer time) as the α-relaxation process evolves on the long-time range (low frequency side) of the JG relaxation process and the strength of the α-relaxation grows at the expense of that of the JG relaxation. The temperature decreases from curve 1 to curve 7. Curve 1 is only for the JG relaxation with β = 1. In curve 2, its β decreases and α-relaxation for which β < 1 develops. In curves 3–7, the strength of the α-relaxation increases at the expense of that of the JG relaxation, β for both decrease and τ 0 increases, more rapidly for the α- than for the JG-relaxation.
The parameters obtained by fitting the Tool-Narayanaswamy-Moynihan formalism for non-exponential, nonlinear structural relaxation to the data for epoxy cyclohexyl POSS-DGEBA and glycidyl POSS-DGEBA mixtures. T g cal is the temperature determined by drawing lines as shown in Fig. 2 . The β cal and x values are within ±0.02, and the T g cal is within ±0.20 K. For the 50%, 75%, and 100% glycidyl POSS-DGEBA mixtures β cal may be less certain than ±0.02 because these mixture have low T g cal and could not be cooled in the instrument to very deep in the glassy state before obtaining the scan.
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