Question

Why do polymers exhibit greater hysteresis when undergoing a phase transition?

Answer 1

generally Many polymeric substrates which swell on adsorption exhibit sorption hysteresis

Hysteresis is the dependence of the state of a system on its history

High hysteresis indicates a high loss of energy (and so is good for energy absorbing applications)

Chemical modification of hydrophilic groups, which markedly alters the amount of water sorbed by keratin, or the filling of possible voids in the substrate has little effect on keratin-water vapor sorption hysteresis. Sorption in swelling systems occurs by a coupled diffusion-relaxation mechanism.

It is demonstrated that the occurrence of hysteresis is associated with the stress relaxation of the cohesive forces opposing swelling. Changes in the structural conformation may be considered as the variable which differs between the adsorption and desorption states. The segmentai mobility of the macromolecular chains plays a major role in the irreversibility of the sorption isotherm, leading to wide diversity in hysteresis effects in polymers.