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Oxidative polymerization of pyrrole on the surface of platelets of graphene oxide (GO) was demonstrated to generate polypyrrole/GO (PPy/GO) hybrid assemblies. The polymerization reactions were performed in GO acid dispersions using ammonium persulfate (APS) as an oxidant. Model kinetic reactions were carried out by 1H NMR spectroscopy with APS at low temperatures. Evidence was found for an increase...
Probe indentation techniques have been widely used to characterize the stiffness-related properties of polymeric materials over the past two decades. However, it still remains challenging to apply these methods for directly measuring the elastic modulus of nanometer-sized polymer films supported by stiff substrates, primarily due to the convolution between the polymer and substrate moduli. Here, we...
Despite the wide range and versatility of polymer-grafting methods to produce biopassive interfaces, commonly applied polymer brushes suffer from an intrinsic lack of long-term stability when incubated in aqueous media under physiological conditions. The robustness of brush films in such environments can be greatly improved by applying a hydrophobic, “protecting” layer between the supporting substrate...
Due to their unique microphase structure copolymer systems have become important potential candidates for nanolitographic purposes. In order to properly design copolymeric templates a complete characterization of the phase separated system is required. Due to the fact that structural analysis of organic compounds remains demanding, especially when it comes to nanometer scale features such as interfacial...
The use of biopolymers in nanotechnologic applications, e.g. as coatings, is often limited by their suboptimal nanomechanical properties. Here we used an atomic force microscopy (AFM) based approach to study the elastic properties and thickness of surface supported DOPC membranes containing varying amounts of bolalipids (C20BAS) at the nanoscale. We found that increasing amounts of bolalipids led...
Various techniques to measure the force-extension relationship of individual polymer chains with the atomic force microscope (AFM) are compared. Reliable stretching force profiles can be obtained with the nano-handling technique, which involves imaging of the measured individual polymer molecules prior and after the force experiment. Results originating from the classical pulling technique, which...
We present a simple method to control the tribological properties of contacts between polymer brushes and a solid counter surface. We show, using atomic force microscopy (AFM) experiments, that the friction force, upon relative sliding of a poly(N-isopropyl acrylamide) (PNIPAM) brush and a gold colloid on an AFM cantilever, varies over two orders of magnitude when changing the composition of an ethanol-water...
S-layer recrystallization is part of, at least, two major scientific and technological challenges: a model system to study 2-D polymer crystal formation and a bottom-up approach to build biomimetic and functional interfaces. In particular, the self-assembly process of the bacterial surface layer protein (SbpA) might be influenced by two different interactions: protein/substrate and protein/protein...
The stiffness-related properties of glassy and rubbery polymer films can behave differently when confined at the nanometer scale. However, direct measurements of the glassy and rubbery modulus of nanometer-sized polymer films are still limited and the existing models for explaining the thickness dependence of the polymer modulus remain in significant disagreement. By means of nanomechanical mapping...
Advancements in processing techniques have facilitated the development of a series of unique high-performance DuPont™ Kevlar® fibers. Directly characterizing interior structures of these fibers is vital for connecting processing variations with resulting mechanical properties. Here we report detailed investigations of processing-internal structure-property relationships among four distinct classes...
We investigated surface structures of three kinds of block copolymer (BCP) specimens forming hard spherical microdomains embedded in a soft matrix, by using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and grazing-incidence small-angle X-ray scattering (GISAXS). The three BCP specimens consist of different chemical species such as SEBS (polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene)...
Crosslinked poly(urea-siloxane) (PUS) copolymer microspheres with diameters ranging from 0.8 to 1.8 μm with diameter polydispersity indices between 1.15 and 1.60 were synthesized in one-step precipitation polymerization in water-acetone solvent mixtures at room temperature. The spheres were obtained using aminopropyl-terminated siloxanes, isophorone diisocyanate and a tetrafunctional isocyanate crosslinker,...
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