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Ceiling temperature () is a measure of the tendency of polymers to revert to their monomers. When a polymer is at its ceiling temperature, the rate of polymerization and depolymerization of the polymer are equal. Generally, the ceiling temperature of a given polymer is correlated to the steric hindrance of the polymer’s monomers. Polymers with high ceiling temperatures are often commercially useful. ==Thermodynamics of polymerization== At constant temperature, the reversibility of polymerization can be determined using the Gibbs free energy equation: : where is the change of entropy during polymerization. The change of enthalpy during polymerization, , is also known as the heat of polymerization, which is defined by : where and denote the activation energies for polymerization and depolymerization, respectively. Entropy is the measure of randomness or chaos. A system has a lower entropy when there are few objects in the system and has a higher entropy when there are many objects in the system. Because the process of depolymerization involves a polymer being broken down into its monomers, depolymerization increases entropy. In the Gibbs free energy equation, the entropy term is negative. Enthalpy drives polymerizations. At low temperatures, the enthalpy term is greater than the term, which allows polymerization to occur. At the ceiling temperature, the enthalpy term and the entropy term are equal. Above the ceiling temperature, the rate of depolymerization is greater than the rate of polymerization, which inhibits the formation of the given polymer. The ceiling temperature can be defined by : 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ceiling temperature」の詳細全文を読む スポンサード リンク
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