Swelling mechanisms elastomeric networks

Characterization of elastomeric networks by swelling equilibrium measurements may take advantage of the applicability of the constrained junction theory already demonstrated for mechanical testing. Use of the interpenetration concept (equation 124 or 125), and of topological expressions for (equations 47 or 60) cause equation (156) to depend only on and x for a perfect network, or on M, M , and x for a randomly cross-linked network. An example of such an application was given by Erman and Baysal. Two cross-linked polystyrene networks were... 

The primary goal of a general statistical theory is to derive an equation of state for the elastomeric molecular network which will hold for any deformation including swelling. Since the major contribution to the elasticity is entropic the molecular interpretation depends on how the stress affects the conformational distribution of an assembly of chains. The successful statistical model will provide predictive relationships between the molecular structure and topology of the network and its macroscopic behavior, e.g., mechanical and swelling responses. 

Network topology affects all of the elastomeric properties, including (i) equilibrium properties such as the modulus, ultimate strength, maximum extensibility and degree of swelling and (ii) dynamic mechanical properties such as viscoelastic losses. The pore or mesh size is a fundamental quantity which characterizes the structure of the insoluble polymer network, and can be taken to be... 

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