Melting of nascent superhigh-molecular-weight poly(ethylene oxide) obtained by means of heterogenous ion-coordinate polymerization

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Abstract
The melting of nascent superhigh-molecular-weight poly(ethylene oxide) (PEO) has been studied by means of differential scanning calorimetry (DSC). High values of the melting temperatures and enthalpies were established. The higher temperatures are explained by the presence of tie molecules in high concentration. The phase transition is accompanied with the absorption of heat in addition to the heat of fusion. This additional heat can be interpreted as follows: (1) a large entropy change in amorphous areas during the transition, caused by disorientation of chains with a long distance between the chain ends in the nascent crystal state, to entangled statistical coils; and/or (2) a large internal energy change in the crystal areas caused by deformation of the crystal lattice under the action of internal stresses, increasing with temperature in the range from solid-plastic crystal transition (50°C) temperature to the melting point.