Elastic behaviour and low-temperature specific heat of linear and reticulated amorphous polymers

The mechanical characteristics in the region of the primary relaxation and the low-temperature specific heats have been measured in linear (bisphenol- A-polycarbonate and polyurethane) and reticulated (a fully cross-linked het erocyclic network) amorphous polymers. The behaviours revealed have been an alysed in order to throw light on their correlation to the polymer morpholo gy. It is found that a cross-linked polymer shows values of fragility, anha rmonicity and low-temperature specific heat which are significantly smaller than those of linear polymers, characterized by weak interchain interactio ns. It is also shown that the fragility appears to scale with the anharmoni city of the system, the less fragile polymer being characterized by the sma llest degree of anharmonicity.