The molecular basis of rubberlike elasticity

Abstract

The purpose of this chapter is to discuss molecular basis of rubberlike elasticity. Rubberlike materials consist of relatively long polymeric chains having a high degree of flexibility and mobility that are joined into a network structure. The requirement of flexibility and mobility is associated with very-high deformability. This chapter discusses the structural features of networks that contribute to the stress upon deformation. It discusses the simple classical models of elasticity and departures from these simple models. It differentiates between two classes of models, the constraint models, which assume that the total elastic energy of the network equals the sum of the individual network chain energies, and the trapped entanglement models, which assume that entanglements that are trapped during the cross-linking stage contribute additionally to the network elastic energy. This chapter also provides the molecular interpretation of coefficients obtained from the phenomenological theories. It discusses recent work on swollen gels and responsive gels. It also discusses the thermoelastic behavior of networks. This chapter closes with a discussion on neutron scattering experiments and some recent experimental studies on the elasticity of single polymer chains.