Alkyl nanodomains

A schematic picture of the structure of semi-crystalline PODMA is shown in the insets of Fig. 12.1. Basic idea is that the alkyl groups belonging to different monomeric units form layer-like alkyl nanodomains which are separated by main chains. The periodicity dnps of this lamellar structure reflected by the prepeak in x-ray scattering data is indicated. We assume that the alkyl groups within the alkyl nanodomains are basically interdigitated and not to far away from an extended chain conformation. This can be concluded from the dependence of the d ps value on the number of alkyl carbons per side chain C for atactic poly(n-alkyl methacrylates) (Fig. 12.2). The dependence of dnps on (7 is nearly linear and the slope is about 0.13 nm [50] per additional CH2 unit in the side chain corresponding to the value reported for extended chain alkanes (0.127 nm/carbon). 

From that moment ionic liquids started to be regarded as fluids formed by a polar domain with the structure of a tridimensional network of ionic channels (the polar network), and nonpolar domain(s) arranged as a dispersed nanophase in the case of ionic liquids with relatively short alkyl-side chains and as a continuous one for longer side-chains (Fig. 6). In the systems first analyzed (1-alkyl-methylimidazolium hexafluorophosphate ionic liquids), the butyl side-chain marked the onset of the transition from dispersed nonpolar nanodomains to a bicontinuous nanosegregated system. The nanosegregation is also observed in other families of ionic liquids, the presence of nonpolar side chains both in the cation or in the anion being determinant in the structure of the ionic liquid (Fig. 7). 

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