Encapsulation of fillers with grafted polymers for model composites

Surface-initiated free radical polymerization at the liquid-liquid interface: a one-step approach for the synthesis of amphiphilic janus silica particles

Amphiphilic Janus silica particles with hydrophobic polystyrene (PS) and hydrophilic poly(sodium methacrylate) (PSMA) brushes on two hemispheres were prepared at the liquid-liquid interface by surface-initiated polymerization. After introduction of free-radical initiator modified silica particles into a mixture of styrene and water, the silica particles were adsorbed at the liquid-liquid interface. One hemisphere of a silica particle is immersed in aqueous phase, and the other one is in styrene phase. After initiation at an elevated temperature, PSMA chains grow on one hemisphere and PS chains grow on the other one. Thermogravimetric analysis and infrared spectra results confirmed the grafting of polymer brushes on the surfaces. Transmission electron microscopy was used to characterize the asymmetric surface structure and aggregation structure of the Janus particles.

Adapting low-adhesive thin films from mixed polymer brushes

The concept of the responsive/adaptive mixed polymer brushes was applied to the development of the thin film coatings possessing low adhesive properties that were evaluated with AFM probes in different media. Mixed brushes composed of polydimethylsiloxane (PDMS) and polyethyleneoxide (PEO) revealed a selective layered segregation in air and water. Immersion of the sample into an aqueous environment drove PEO chains to the brush-water interface while upon drying the surface undergoing reconstruction and was occupied with PDMS. Low interfacial energies of PDMS in air and PEO in water provided low-adhesive properties of the PDMS-PEO brushes to the probes in both media due to the spontaneous and rapid reconstruction of the mixed brush.

"Chemical transformers" from nanoparticle ensembles operated with logic

The pH-responsive nanoparticles were coupled with information-processing enzyme-based systems to yield "smart" signal-responsive hybrid systems with built-in Boolean logic. The enzyme systems performed AND/OR logic operations, transducing biochemical input signals into reversible structural changes (signal-directed self-assembly) of the nanoparticle assemblies, thus resulting in the processing and amplification of the biochemical signals. The hybrid system mimics biological systems in effective processing of complex biochemical information, resulting in reversible changes of the self-assembled structures of the nanoparticles. The bioinspired approach to the nanostructured morphing materials could be used in future self-assembled molecular robotic systems.

Single nanoparticle plasmonic devices by the "grafting to" method

Hierarchically organized single-nanoparticle structures synthesized in this work consisted of a 200 nm silica core and a pH-responsive poly(2-vinylpyridine) shell decorated with 15 nm gold nanoparticles. pH changes in the range of 3-6 back and forth results in a swelling-shrinking polymer brush shell and, thus, in the tuning distance between noble nanoparticles. A change in the interparticle distance is accompanied by a very pronounced shift in the maximum wavelength of the surface plasmon absorption peak. The dispersion of the resulting composite nanoparticles reversibly changed color from red to purple-blue as the pH changed from 2.5 to 6. Such hierarchically assembled nanostructures can be used as free-standing single-particle sensors in various miniaturized analytical systems.

Cotton Fibers Encapsulated with Homo- and Block Copolymers: Synthesis by the Atom Transfer Radical Polymerization Grafting-From Technique and Solid-State NMR Dynamic Investigations

Cotton fibers were modified by surface-initiated atom transfer radical polymerization of ethyl acrylate (EA) followed by copolymerization with styrene. Either ethyl 2-bromopropionate as a sacrificial free initiator or Cu(II) as a deactivator was used to optimize the EA grafting yield and to preserve the livingness of the chain ends for the subsequent growth of a poly(styrene) (PSty) block from the poly(ethyl acrylate) (PEA) grafts. The polymer-encapsulated cotton fibers were analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry (DSC), thermogravimetric analysis, and solid-state NMR (high-resolution 13C cross-polarization magic angle spinning, 1H spin-lattice relaxation times, and 1H free induction decay analysis NMR). The latter allowed the detection of the dynamic modifications associated with the presence of homo- and block copolymer grafts. In particular, the results of the DSC and NMR investigations suggest a heterogeneous morphology of the g-PEA-b-PSty grafted skin, which could be described as an inner layer of g-PEA sandwiched between the semicrystalline cellulose of the core fiber and the high glass transition temperature PSty of the covalently linked outer layer. Such morphology results in a reduced molecular mobility of the PEA chains.