Supercooling fractional

Between T j, and Tg, depending on the regularity of the polymer and on the experimental conditions, this domain may be anything from almost 100% crystalline to 100% amorphous. The amorphous fraction, whatever its abundance, behaves like a supercooled liquid in this region. The presence of a certain degree of crystallinity mimics the effect of crosslinking with respect to the mechanical behavior of a sample. 

Secondly, fractionation effects have been studied [126] where now the components are the various molecular weights in the solution. They conclude that fractionation will be important even at high molecular weights due to the variation in supercooling of the different molecular weights, and hence their different growth rates. Notice that this result could well be affected by the definition of supercooling as described in Sect. 2.3. 

Fig. 3.19. Growth rate as a function of supercooling for sharp fractions of different molecular weights...

Differential scanning calorimetry measurements have shown a marked cooling/heat-ing cycle hysteresis and that water entrapped in AOT-reversed micelles is only partially freezable. Moreover, the freezable fraction displays strong supercooling behavior as an effect of the very small size of the aqueous micellar core. The nonfreezable water fraction has been recognized as the water located at the water/surfactant interface engaged in solvation of the surfactant head groups [97,98]. 

Heats of fusion, AHfus, are generally expressed in kcal/mol or kJ/mol and entropies of fusion, ASlus in cal/mol-K (e.u. or entropy unit) or J/mol K. The fugacity ratio F, as discussed in Section 1.2.8, is used to calculate the supercooled liquid vapor pressure or solubility for correlation purposes. In the case of liquids such as benzene, it is 1.0. For solids it is a fraction representing the ratio of solid-to-liquid solubility or vapor pressure. 

As mentioned in Sect. 3, for PEO it has been found that the crystallization temperature is often a function of the MD volume. The examples quoted in Sect. 3 referred to PEO dispersed in droplets or to PEO that was a component within diblock copolymers. For other block copolymer components like PCL the variation in Tc encountered upon MD size increase is not as pronounced. Nojima et al. [22] found that the variation of Tc for PB-fo-PCL block copolymers with spherical PCL MDs of increasing sizes, ranging from 10.3 to 17.4 nm, was of about 5 °C for crystallization at very large supercoolings (Tc fluctuated between - 50 and - 45 °C approximately). For ABC triblock copolymers, Muller et al. [29], Schmalz et al. [101,119] and Balsamo et al. [118] found, by studying copolymers with minority components of PEO or PCL blocks linked to a rubbery block, that the Tc associated with fractionated... 

The cooled reaction product is treated with 200 cc. of water, the layer of oil separated, washed once with a second portion of water, and subjected to distillation in vacuo. The first fraction of the distillate contains benzyl alcohol together with unchanged aldehyde, as well as a small quantity of water. The temperature then rises rapidly to the boiling-point of benzyl benzoate, when the receivers are changed. The product boils at 184-185°/15 mm., and analysis by saponification shows it to consist of 99 per cent ester. A yield of 410-420 g. is obtained, which corresponds to 90-93 per cent of the theoretical amount. This benzyl benzoate supercools readily, but after solidifying... 

In this equation, X2 represents the mole fraction of naphthalene in the saturated solution in benzene. It is determined only by the chemical potential of solid naphthalene and of pure, supercooled liquid naphthalene. No property of the solvent (benzene) appears in Equation (14.45). Thus, we arrive at the conclusion that the solubility of naphthalene (in terms of mole fraction) is the same in all solvents with which it forms an ideal solution. Furthermore, nothing in the derivation of Equation (14.45) restricts its application to naphthalene. Hence, the solubility (in terms of mole fraction) of any specified solid is the same in all solvents with which it forms an ideal solution. 

The classic example of a NEAS is a supercooled liquid cooled below its glass transition temperature. The liquid solidifies into an amorphous, slowly relaxing state characterized by huge relaxational times and anomalous low frequency response. Other systems are colloids that can be prepared in a NEAS by the sudden reduction/increase of the volume fraction of the colloidal particles or by putting the system under a strain/stress. 

Purified by careful fractionation in vacuo. The distillate remains supercooled for several days before solidifying. It is a slightly hygroscopic solid which could melt in the hand. It has a pKa jf j gg H2O. The picrate has m 149-151° (from EtOH). [Taylor and Corvetti Org Synth Coll Vol IV 654 1963 IR Katritzky et al. JCS 3680 7959 Jaffe and Doak JACS 77 4441, 4481 1955 Boekelheide and Linn JACS 76 1286 1954]. 

---