Measurement by differential scanning

Onset value as measured by differential scanning calorimetry. 

Common examples of the high Tg macromers are based on polystyrene or polymethylmethacrylate (PMMA) polymers of sufficiently high molecular weight to have a high T (typically on the order of 70-100°C as measured by differential scanning calorimetry) and also to make them immiscible with the acrylic polymer backbone once the solvent or heat has been removed. Typical molecular weight of the polystyrene or PMMA macromers is on the order of 5000-10,000 Da. Their generic structure can be pictured as in Fig. 13 (shown there for polystyrene). 

The photostability of two polymorphs of nicardipine hydrochloride have been studied using a number of techniques [95]. After irradiation, the drug substance decomposes to a pyridine derivative, and the photodegradation of the /1-form exceeded that of the x-form. It was also found that the color of the two different forms differed with the polymorphic state, but that grinding the two forms lessened the difference in their photochemistries. A correlation between the heat of fusion (measured by differential scanning calorimetry) and the photodegradation rate constant was observed. 

The thermal unfolding of proteins is best measured by differential scanning calorimetry, which measures the heat absorbed by a protein as it is slowly heated through its melting transition (Figure 17.1). A solution of about 1 mg of protein in 1 mL of buffer and a separate reference sample of buffer alone are heated electrically.6 The additional current required to heat the protein solution is recorded. As the protein denatures, there is a large uptake of heat because the process is highly endothermic. The temperature at the maximum of the peak is... 

The thermal properties measured by differential scanning calorimetry (Table IV) provide no structural information in the DMP-MPP system. Neither of the two homopolymers undergoes thermally-induced... 

Walkley, K.1972. Bound water in stratum comeum measured by differential scanning calorimetry. 

A constant strain rate of 10% per minute was employed. Polymers were isolated by air drying or freeze drying and molded at 150°C into dumbbell speciments for the tensile measurements. Glass transition temperatures (Tg) were measured by differential scanning calorimetry. 

Glass transition temperatures were measured by differential scanning calorimetry (DSC) using a DuPont 900 Differential Thermal Analyzer. The samples were cooled to -100°C in a closed pan and then scanned to 150°C at a rate of 15°/minute. 

Fig. 3.1 Phase diagram for 1 -alkyl-3-methylimidazolium tetrafluorob-orate showing the melting ( ), glass (o) and clearing ( ) transitions measured by differential scanning calorimetry. Data from Ref. [16].

Thermochemical data were required for the estimation of ground state strain. Heats of formation ( 0.5 kcal mol-1) were obtained by the experimental determination of heats of combustion 25 -27) using either a stirred liquid calorimeter 25) or an aneroid microcalorimeter 26) heats of fusion and heat capacities were measured by differential scanning calorimetry (DSC), heats of vaporization 21, 25, 27) by several transport methods, or they were calculated from increments 28). For the definition of the strain enthalpies Schleyer s single conformation increments 29) were used and complemented by increments for other groups containing phenyl30) and cyano substituents. 

A shortening in relaxation time in the critically strained region makes some materials tough. The shift of relaxation time is attributed to strain-induced dilatation and can reach as much as five decades. Thermal history, on the other hand, dictates the initial state from which this dilatation starts and may be expressed in terms of excess entropy and enthalpy. The excess enthalpy at Tg is measurable by differential scanning calorimetry. Brittle to ductile transition behavior is determined by the strain-induced reduction in relaxation time, the initial amount of excess entropy, and the maximum elastic strain that the material can undergo without fracturing or crazing. 

Eliasson and Ljunger (33) reported that the cationic surfactant cetyl trimethyl-ammonium bromide (CTAB) slowed down the rate of formation of amylopectin crystallites in gelatinized waxy maize starch, as measured by differential scanning calorimetry (DSC). 

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