Photonic Crystal Films Based on Polymer Particles with a Core/Shell Structure Responding to Ethanol.

Responsive photonic crystals assembled from colloidal particles have been increasingly utilized in detection and sensing devices owing to their attractive ability to change color in response to external conditions. Methods of semi-batch emulsifier-free emulsion and seed copolymerization are successfully applied for the synthesis of monodisperse submicron particles with a core/shell structure, a core being formed by polystyrene or poly(styrene-co-methyl methacrylate) and a shell being formed by poly(methyl methacrylate-co-butyl acrylate). The particle shape and diameter are analyzed by the dynamic light scattering method and scanning electron microscopy, and the composition is investigated by ATR-FTIR spectroscopy. As shown by scanning electron microscopy and optical spectroscopy, the thin-film 3D-ordered structures based on poly(styrene-co-methyl methacrylate)@poly(methyl methacrylate-co-butyl acrylate) particles exhibited the properties of photonic crystals with minimum number of defects. For polymeric photonic crystal structures based on core/shell particles, a pronounced solvatochromism with respect to ethanol vapor (less than 10 vol %) is observed. Moreover, the nature of the crosslinking agent has a significant effect on the solvatochromic properties of 3D-ordered films.

Hydrophilic polyelectrolyte microspheres as a template for poly(3,4-ethylenedioxythiophene) synthesis.

Conducting polymer polyelectrolyte microspheres are typically composed of a cationic conducting polymer and an anionic polymer. The polymer chains inside these microspheres are physically or chemically cross-linked, creating a network that enables high water retention. Poly(3,4-ethylenedioxythiophene) (PEDOT) being an electrically conductive polymer exhibits a high conductivity and has great biotechnological applications. The unique combination of properties of PEDOT containing polyelectrolyte microspheres makes them widely investigated materials for electroresponsive cells, tissue engineering, and bio-sensors. The demand to produce PEDOT with varied properties depending the specific application requires the understanding of the basic principles of template formation. In the present work, we studied the inverse suspension polymerization of p-styrenesulfonic acid in the presence of a cross-linking agent as a synthetic way for the formation of porous polyelectrolyte microspheres. We traced how the nature of the emulsifier affected both the structure of the surface layer of the microspheres and the degree of their cross-linking. The porous structure of polyelectrolyte microspheres obtained is found to promote the polymerization of EDOT in their presence throughout the entire microsphere volume. The structural characteristics of the polyelectrolyte/PEDOT complexes in relation to their electrochemical properties have been studied.

Sulfonic Cryogels as Innovative Materials for Biotechnological Applications: Synthesis, Modification, and Biological Activity.

Polymeric hydrogels based on sulfo-containing comonomers are promising materials for biotechnological application, namely, for use as a system for delivering water and minerals during seed germination in conditions of an unstable moisture zone. In this work, cryogels based on 3-sulfopropyl methacrylate and 2-hydroxyethyl methacrylate copolymers were obtained by the cryotropic gelation method. The morphology, specific surface area, and swelling behaviors of cryogels are found to depend on the total concentration of monomers in the reaction system and the content of the gel fraction in cryogels. Cryogels formed in the presence of nanodiamonds are shown to exhibit high biological activity during the germination of Lepidium sativum L. variety Ajur seeds, which manifests itself by stimulating seed germination and a significant increase in the raw weight of sprouts. These results indicate that sulfonic cryogels have a high potential to improve seed germination and plant growth, proving that such cryogels can be used as environmentally friendly materials for agricultural applications.

Influence of the Nature and Structure of Polyelectrolyte Cryogels on the Polymerization of (3,4-Ethylenedioxythiophene) and Spectroscopic Characterization of the Composites.

Conductive hydrogels are polymeric materials that are promising for bioelectronic applications. In the present study, a complex based on sulfonic cryogels and poly(3,4-ethylenedioxythiophene) (PEDOT) was investigated as an example of a conductive hydrogel. Preparation of polyacrylate cryogels of various morphologies was carried out by cryotropic gelation of 3-sulfopropyl methacrylate and sulfobetaine methacrylate in the presence of functional comonomers (2-hydroxyethyl methacrylate and vinyl acetate). Polymerization of 3,4-ethylenedioxythiophene in the presence of several of the above cryogels occurred throughout the entire volume of each polyelectrolyte cryogel because of its porous structure. Structural features of cryogel@PEDOT complexes in relation to their electrochemical properties were investigated. It was shown that poly(3,4-ethylenedioxythiophene) of a linear conformation was formed in the presence of a cryogel based on sulfobetaine methacrylate, while minimum values of charge-transfer resistance were observed in those complexes, and electrochemical properties of the complexes did not depend on diffusion processes.

A common optical approach to thickness optimization in polymer and perovskite solar cells.

The structure of experimentally designed solar cells was optimized in terms of the photoactive layer thickness for both organic bulk heterojunction and hybrid perovskite solar cells. The photoactive layer thickness had a totally different behavior on the performance of the organic and hybrid solar cells. Analysis of the optical parameters using transfer matrix modeling within the Maxwell-Garnett effective refractive index model shows that light absorbance and exciton generation rate in the photoactive layer can be used to optimize the thickness range of the photoactive layer. Complete agreement between experimental and simulated data for solar cells with photoactive materials that have very different natures proves the validity of the proposed modeling method. The proposed simple method which is not time-consuming to implement permits to obtain a preliminary assessment of the reasonable range of layer thickness that will be needed for designing experimental samples.

Cross-linked polyelectrolyte microspheres: preparation and new insights into electro-surface properties.

Polyelectrolyte microspheres find applications in many fields such as ion exchange columns, fuel cell membranes, and catalysis, to name a few. Synthesis of these microspheres by inverse emulsion polymerization offers various advantages due to the increased specific surface area and high surface charge density. The surface charge density of the obtained polyelectrolyte microspheres is a hundred times higher than that of either particles obtained by dispersion copolymerization of styrene and styrenesulfonic acid or sulfonated microspheres. The morphology, chemical structure, and electro-surface properties of the synthesized microspheres were studied by transmission and scanning electron microscopy, FTIR-spectroscopy, and conductometric and potentiometric titrations, respectively. Using the potentiometric titration it is possible to characterize the structure of the surface layer of polyelectrolyte microspheres as entirely as possible. The study of the ion-exchange capacity of polyelectrolyte microspheres shows that ion-exchange capacity is 2.1 meq g-1 in this case, which is more than 2 times higher than that of sulfonated microspheres, and 20 times higher than that of particles obtained by dispersion copolymerization.

Microfluidic synthesis of monodisperse porous polystyrene microspheres for sorption of bovine serum albumin.

Droplet microfluidics offers exquisite control over the flows of multiple fluids in micro-scale, enabling fabrication of advanced microspheres with precisely tuneable structures. The main goal of this work was to design monodispersed carboxylated polystyrene microspheres with a developed pore structure (a specific surface area more than 200 m2/g) using microfluidic technology. We investigated the influence of the composition of monomer phase for the stable formation of droplets. Under the stable region, the resulting microspheres (with diameter 50 µm) showed narrow size distribution having a coefficient of variation of below 2%. The obtained microspheres are characterised by morphology and surface structure by means of electron microscopy. The structure of cross-linked microspheres is investigated by solid-state 1H NMR spectroscopy. Finally, these microspheres have great potential for the effective sorption of biologically active substances (bovine serum albumin).