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How do long polymer chains produce elasticity in rubber?

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Figure 1: The position vector x and the velocity vector v of a material point, the body force fdV acting on an element dV of volume, and the surface force TdS acting on an element dS of surface in a Cartesian coordinate system 1, 2, 3 (see text).
mechanics of solids Figure 1: The position vector x and the velocity vector v of a material point, the body force fdV acting on an element dV of volume, and the surface force TdS acting on an element dS of surface in a Cartesian coordinate system 1, 2, 3 (see text).

At the microscopic level, the elasticity of rubber is derived from the unique behavior of its long-chain polymer molecules. These molecules are highly flexible and naturally configure themselves into random, coillike shapes.12

When rubber is subjected to stress, these long chains uncoil and extend. Because the molecules are flexible and possess little internal hindrance to the motion of their subunits, they can be stretched to great lengths. When the external force is removed, the chains spontaneously recoil, returning to their original disordered, coillike state through the random motion of their repeating units.134

For these materials to function effectively as rubber, they must remain in this flexible state and avoid becoming "glassy" or spontaneously crystallizing at normal temperatures. Additionally, commercial rubber is often subjected to vulcanization, a process that creates chemical cross-links between the polymer chains. This network of interlinks prevents the molecules from sliding past one another and flowing like a liquid, ensuring that the material maintains its shape and recovers its original form after deformation.45