The influence of ionic complexes on phase behavior of PS-b-PMMA copolymers over a wide range of molecular weights and PS volume fractions was investigated by small-angle X-ray scattering (SAXS), grazing incidence small-angle X-ray scattering (GISAXS), transmission electron microscopy (TEM), and neutron reflectivity (NR). The disorder-to-order transition (DOT) in both symmetric and asymmetric copolymers indicates that the overall Flory−Huggins segmental interaction parameter, χeff, between polystyrene (PS) and poly(methyl methacrylate) (PMMA) blocks with lithium−PMMA complexes is increased compared to that of the neat copolymers. This enhanced χeff further results in an order-to-order transition (OOT), from spheres to cylinders, and an increase in the ordering and spacing of microdomains. Moreover, transitional metal ionic complexes, such as copper−PMMA complexes, are found to have the similar influence on phase behavior of PS-b-PMMA copolymers. The formation of ionic complexes in the copolymers not only offers a parameter to tune the degree of microphase separation of PS-b-PMMA copolymers but also provides a way to fabricate multifunctional materials.

We investigate the mechanism of polyelectrolyte multilayer (PEM) assembly in nanoporous templates with a view to synthesizing nanotubes or nanowires under optimal conditions. For this purpose, we focus on the effect of parameters related to the geometrical constraints (pore diameter), the size of the macromolecules (their molar mass and the ionic strength), and the interaction between the pore walls and the adsorbed chains (modulated by the ionic strength). Our results reveal the existence of two regimes in the mechanism of PEM growth: (i) the first regime is comparable to that observed on flat substrates, including the influence of ionic strength and (ii) the second regime, which is slower in terms of kinetics, results from the interconnection established between polyelectrolyte chains across the pores and leads to the formation of a dense gel. As a consequence, the diffusion of polyelectrolytes in nanopores becomes the controlling factor of PEM growth in this second regime. The dense gel, owing to its peculiar structure, enhances the formation of nanowires or of partially occluded nanotubes in some cases, depending on initial pore dimensions.

Nanotubes made from a fibrillar protein, namely, collagen, were fabricated by a template-based method combined with layer-by-layer (LbL) deposition. The ability to incorporate collagen in LbL multilayered film was first demonstrated by in situ quartz crystal microbalance and ex situ ellipsometry on a flat model substrate, using poly(styrene sulfonate) (PSS) as polyanion. Collagen-based nanotubes were then fabricated by alternately immersing a polycarbonate membrane, used as template, in PSS and collagen aqueous solutions. Direct evidence for nanotube formation was obtained by dissolving the membrane and imaging the liberated (PSS/collagen)(n) nanostructures by scanning electron microscopy and by transmission electron microscopy. The proposed strategy constitutes a practical alternative to electrospinning as it allows a very good control over the dimensions (outside and inside diameters and length) of the resulting nanotubes. Besides their fundamental interest, collagen-based nanotubes are useful nano-objects for the creation of new nanostructured biomaterials with numerous potential applications in the biomedical field.

The membrane-templating method was successfully combined with electrodeposition and layer-by-layer assembly to create various multisegmented nanostructures composed of metal, polymers, synthetic and biological polyelectrolytes, and colloids. The electrochemical approach offers the control over the architectural parameters of the resulting structures (in particular the segment length and morphology), whereas the LbL adsorption technique permits to integrate nonconducting materials, including biomacromolecules, within the nanostructures. A supplementary degree of complexity can be reached by capping or loading the LbL nanotubes with colloidal particles. The ability to easily generate such hybrid anisotropic nanoparticles with spatially resolved chemical, physical, and biochemical functionalities is a boon for the synthesis of nanostructures, which is of tremendous importance for electronic, sensing, drug delivery, and modern biomedical and biotechnological applications.