Polymer temperature-dependent switching

A compound with a highly temperatine-dependent property, such as solubility, is said to be thermomorphic. There are a variety of other catalyst systems that can be recovered on the basis of temperature-dependent solubilities, usually involving polymers [13-18]. Attention has also been given to nonthermal solubility switches . These include photochemically and chemically triggered precipitons [19-25], and the use of CO2 pressure to regulate solubilities [26-28]. The latter protocol is particularly suited to liuorous compounds. 

The oxidative induction time (OIT) is measured by first heating the polymer sample while keeping it in a nitrogen atmosphere to a high temperature, typically 200°C for polyethylene. After the establishment of constant temperature, the atmosphere is switched to oxygen and the time (OIT) to the start of an exothermic (oxidation) process is measured (Fig. 10.23). It has been shown that the OIT exhibits an Arrhenius temperature dependence and that there is a linear relationship between OIT and the content of efficient antioxidant. This follows from the fact that... 

Measuring the relative oxidative stability of polymers is important. Measurements can be used to determine dependencies on structural and molecular weight/weight distribution or the effectiveness of an antioxidant, or to perhaps assess the amount present in a polymer sample, etc. The preferred and commonest method consists in raising the sample temperature to a predetermined level, while in an inert atmosphere, then switching the atmosphere to air or oxygen. The time to the onset of exothermic reaction is measured. 

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