Glass transition activation energy

The increase in the length of the side chain results normally in an internal plasticization effect caused by a lower polarity of the main chain and an increase in the configurational entropy. Both effects result in a lower activation energy of segmental motion and consequently a lower glass transition temperature. The modification of PPO with myristoyl chloride offers the best example. No side chain crystallization was detected by DSC for these polymers. 

The rates of chemical reactions increase with temperature due to the greater proportion of molecules which have energies in excess of the activation energy and this will apply to radiation-induced secondary reactions in polymers. However, solid polymers are also characterized by their glass and melting transition temperatures. Substantial changes in molecular mobility occur across these transitions and the rates of chemical reactions are frequently greatly affected. 

The kinetics of the transition from Graham s glass to trimetaphosphate crystals follow Stranski and Kaischew s theory of crystallization (157, 277) and yield an activation energy of 62.9 kcal/mole (124). Trimetaphosphate occurs as the equilibrium phase in the system NaP03—H20 at between 450° and 620°C (199). 

---