Supramolecular structure, rubber

There is overwhelming evidence that the aramide fibres possess a radially oriented system of crystalline supramolecular structure (see Fig. 19.1). The background of the properties, the filament structure, has been studied by Northolt et al. (1974-2005), Baltussen et al. (1996-2001), Picken et al. (2001), Sikkema et al. (2001, 2003), Dobb (1977-1985) and others. The aramid fibres (and the "rigid" extended chain fibres in general) are exceptional insofar as they were - with the rubbers - the first polymer fibres whose experimental stress-strain curve can very well be described by a consistent theory. 

Whether or not a polymer is likely to be an effective rubber, as opposed to being for example, a glass, a leatherlike material, a wax, a grease or an oil will, on the other hand, entirely depend on the molecular and supramolecular structure. In order to exhibit effective rubbery properties there are three primary requirements concerning structure ... 

A number of polymeric systems exhibit elastomeric properties. In each case, the molecular motion characteristic of rubbers is sensitive to the molecular and supramolecular structure. Two interesting, and commercially important, examples worthy of further discussion are polyurethanes and polysiloxanes, or silicone rubbers. 

The analysis of data on the influence of Xe on the initial rate of rubber-oligomer system Cluing (see Part 2.8.1) shows that modifications in supramolecular structure in the Xex period are reversible. However, oligomers show other examples as well. 

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