The tube model theory of rubber elasticity

Rubbers are highly elastic solids formed by the random permanent linkages between long chain polymers. Their elasticity is largely entropic in origin, so that the molecular theory is largely a matter of counting the configurations available to the polymers and how this number changes under deformation. To do this one needs to know the way in which the crosslinks are formed, which need not be related to any equilibrium process, and to know the restriction placed on the chains by one another's presence, i.e. their entanglements. Recent theoretical developments suggest that the problem is by no means as intractable as it might at first sight appear, and simple models of tube confinement seem to give very good agreement with experiment.