Microscopic theory of rubber elasticity

Area of Science:

• Polymer physics
• Materials science
• Theoretical chemistry

Background:

• Classical polymer elasticity theories often neglect interchain interactions.
• Understanding nonclassical contributions to mechanical response is crucial for advanced materials.

Purpose of the Study:

• To develop a microscopic integral equation theory for polymer liquid and network elasticity.
• To investigate the impact of interchain repulsive interactions and packing correlations on mechanical properties.

Main Methods:

• Integral equation theory applied to polymer liquids and networks.
• Development of a nonclassical intermolecular contribution to the linear modulus.
• Comparison with computer simulations and experimental data.

Main Results:

• Predicted strain-induced softening and a significant intermolecular contribution to the linear modulus.
• Intermolecular contribution becomes dominant in melt states and near isotropic-nematic transitions.
• Observed good agreement with simulations for stress-strain curves and nematic order parameters.
• Found quadratic dependence on segmental concentration and fractional power law on degree of polymerization.

Conclusions:

• The developed theory accurately captures nonclassical elasticity in polymers, particularly near phase transitions.
• The theory provides a framework for understanding structure, thermodynamics, and mechanical response in nematic elastomers.
• Limitations include not explicitly accounting for quenched crosslinks and trapped entanglements.