Amphiphilic single and double networks: a small-angle X-ray scattering investigation

We investigated the microphase-separated morphologies of water-swollen amphiphilic single and double polymer networks using small-angle X-ray scattering (SAXS). The networks consist of (i) a first conetwork containing hydrophobic blocks from either 2-ethylhexyl methacrylate (EHMA) or lauryl methacylate (LauMA) and hydrophilic blocks from 2-(dimethylamino)ethyl methacrylate (DMAEMA) and (ii) a second polyacrylamide (PAAm) network. The SAXS curves are modeled by spherical core-shell micelles, where densely packed hydrophobic cores are surrounded by swollen hydrophilic chains. The correlation between these hydrophobic cores is described using a hard-sphere structure factor. A Porod law and an Ornstein-Zernike structure factor are adopted to capture the strong forward scattering due to large-scale inhomogeneities and the correlation between polymer strands, respectively. The size of the hydrophobic cores depends on the degree of polymerization of the hydrophobic block: for medium and long hydrophobic blocks, several hydrophobic cores merge together to form a larger core. When the second PAAm network is present, the nanostructures of the first amphiphilic network are less well-defined.