Mechanical Properties

· For macromolecular materials, the configurational entropy of a "tangled" molecule contributes to the elastic response of the solid with the cross-link density being an important parameter.

From: Van Vlack, "Elements of Materials Science and Engineering," Addison Wesley (1989)

· The diagram shows a macromolecule at zero stress and under an applied tensile stress. The equilibrium separation between the free ends of the unstressed macromolecule: L = a(n)^0.5 , where n is the number of segments in the molecule, and random orientation of the segments of length, a,is assumed.
· When the material is elastically deformed, the length between the free ends changes and so does the energy of the system.