Nanophase separated amphiphilic conetwork coatings and membranes

Covalently surface-attached coatings and free-standing membranes of some 20 mu m in thickness were prepared by photocopolymerization of a bitelechelic methaerylate-terminated poly(dimethylsiloxane) (PDMS) and silyl-protected 2-hydroxyethyl acrylate. After cleaving the silyl groups, the resulting amphiphilic conetworks exhibit two nanoseparated phases in bulk as well as on their surface as shown by atomic force microscopy (AFM). Thereby, the surface structure is controlled by the chemical nature of the surface covering material. Comparing the swelling behavior of 1D swelling of the coatings with the 3D swelling of the membranes revealed perfect interconnectivity of the hydrophilic phase in all compositions prior to and after water treatment. The hydrophobic PDMS phase, on the other hand, is not interconnected in dry state at compositions with less than 80 wt % PDMS. Diffusion experiments indicate that the PDMS phase reorganizes upon swelling and becomes continuous at PDMS contents of about 50 wt % and more.