Abstract

We will discuss the formation and properties of surface-grafted monolayer and macromolecular assemblies with position-dependent physico-chemical characteristics on flat substrates. In the first part of the presentation, I will present results from high resolution X-ray synchrotron measurements in combination with computer simulation studies, which establish that vapor deposition of organosilanes under confinement follows “propagating front” mechanism rather than conventional diffusion. These wavefronts do not follow the constant width predicted by mean-field growth models widely assumed to model such ‘self-propagating’ or ‘autocatalytic’ growth processes. Instead, the interface progressively roughens in time and this interfacial broadening is described by a power-law growth, corresponding to the propagating front motion. Properties of wavefronts propagating from a single direction as well as those involving counter-propagating wavefronts involving different chemical moieties will be discussed. In the second part, I will describe methods for generating polymer assemblies comprising gradual variation of grafting density () and molecular weight (MW) of the grafted polymers. A simple extension of the latter approach will facilitate the generation of surface grafted block copolymers with gradually varying compositions. I will document that by combining the individual gradients, i.e.  and MW, one can produce complex substrates in which two material properties change independently in two orthogonal directions. I will demonstrate that such multivariant polymer brush assemblies represent universal soft material scaffolds that can be utilized in adjusting the spatial distribution of non-polymeric objects, such as nanoparticles and proteins, and can be used in controlling the adhesion of living cells on surfaces and studying the phase behavior of multicomponent surface-tethered polymer assemblies.