Effects of Junction Functionality

Dependence of Mooney-Rivlin ratio, 2C2/2C1, on the molecular weight between cross links. The factor 2C measures the departure from affineness as the elongation increases, and 2Cj approximates the high-deformation modulus. The ratio decreases with decrease in network chain molecular weight, and with increase in junction functionality, as predicted by theory.  

End linking by an addition reaction between vinyl groups at the ends of a polymer chain and the active hydrogen atoms on silicon atoms in an oligomeric poly(methyl hydrogen siloxane). The case shown gives a junction functionality, j , of six. 

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Llorente, M. A. Andrady, A. L. Mark, J. E., Model Networks of End-Linked Polydimethylsiloxane Chains. Xlll. The Effects of Junction Functionality on the Elastic Properties of the Bimodal Networks. Coll. Polym. Sci. 1981,259, 1056-1061. 

Effects of Junction Functionality. End linking of chains with linkers of a known functionality is used to control the structure in this way. Increasing the junction functionality decreases the fluctuation amplitudes of the junctions in the undeformed state. A network with suppressed junctions behaves close to an affine network under deformation. However, the affineness diminishes under increasing extension. Trifimctional and tetrafunctional PDMS networks prepared in this way have been used to test the molecular theories of rubber... 

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