Templeting of Thin Films Induced by Dewetting on Patterned Surfaces

The instability, dynamics and morphological transitions of patterns in thin liquid films on periodic striped surfaces (consisting of alternating less and more wettable stripes) are investigated based on 3-D nonlinear simulations that account for the inter-site hydrodynamic and surface-energetic interactions. The film breakup is suppressed on some potentially destabilizing nonwettable sites when their spacing is below a characteristic lengthscale of the instability, the upper bound for which is close to the spinodal lengthscale. The thin film pattern replicates the substrate surface energy pattern closely only when, (a) the periodicity of substrate pattern matches closely with the characteristic lengthscale, and (b) the stripe-width is within a range bounded by a lower critical length, below which no heterogeneous rupture occurs, and an upper transition length above which complex morphological features bearing little resemblance to the substrate pattern are formed.Comment: 5 pages TeX (REVTeX 4), other comments: submitted to Phys. Rev.Let

Self-assembled interpenetrating networks by orthogonal self assembly of surfactants and hydrogelators

Interpenetrating networks (IPN) consist of two or more networks of different components which are entangled on a molecular scale and cannot be separated without breaking at least one of the networks. They are of great technological interest because they allow the blending of two or more otherwise incompatible properties or functions, and furthermore synergistic effects might arise from the simultaneous operation of the two networks. So far, the preparation of interpenetrating network gels by self-assembly approaches was doomed to fail because the conventional polymers and surfactant building blocks either phase separate or form mixed assemblies, respectively. Here we report on self-assembled interpenetrating networks obtained by the orthogonal self-assembly of small molecular hydrogelators and surfactants. Preliminary studies on the self-assembly behaviour and viscoelastic properties of these systems revealed that these self-assembled IPN have a number of intriguing properties. For instance, the presence of two coexisting networks offers new possibilities for compartmentalization, and will allow one to adjust the viscoelastic properties between ‘soft’ and ‘hard’ gels. The non-covalent character of such IPN makes their formation fully reversible, which can be exploited for dual responsive systems. Most interestingly, self-assembled IPN can also act as a very primitive, yet unique, model for biological interpenetrating networks like the extracellular matrix and the cytoskeleton, and thereby contribute to our understanding of these very complex systems.DelftChemTechApplied Science