Volodymyr Boyko

Bio: Volodymyr Boyko is an academic researcher from Dresden University of Technology. The author has contributed to research in topics: Dynamic light scattering & Methacrylate. The author has an hindex of 18, co-authored 32 publications receiving 1128 citations.

Temperature‐, pH‐, and Magnetic‐Field‐Sensitive Hybrid Microgels

Abstract: We demonstrate a simple route for the preparation of novel hybrid particles with multiple sensitivities. Aqueous polymeric microgels are modified by magnetite nanoparticles in the preparation of temperature- and pH-sensitive hybrids with a high magnetic response. Up to 15 wt % of magnetite nanoparticles are loaded into microgels. The influence of the amount of magnetite in the microgel structure on the morphology and colloidal properties is discussed. The presence of the magnetite nanoparticles in the microgel decreases its degree of swelling and shifts the volume phase-transition temperature to higher values. Nanostructured composite films with controlled morphologies can be prepared by water evaporation and deposition of the hybrid microgels on a solid substrate.

Temperature-Sensitive Hybrid Microgels with Magnetic Properties

Abstract: In the present paper, we report the preparation of hybrid temperature-sensitive microgels which include magnetite nanoparticles in their structure. Polymeric microgels have been prepared by surfactant-free emulsion copolymerization of acetoacetoxyethyl methacrylate (AAEM) and N-vinylcaprolactam (VCL) in water with a water-soluble azo-initiator. The obtained microgels possess a low critical solution temperature (LCST) in water solutions, with a rapid decrease of the particle size being observed at elevated temperatures. Magnetite was deposited directly into microgels, leading to the formation of composite particles which combine both temperature-sensitive and magnetic properties. The influence of magnetite load on microgel size, morphology, swelling-deswelling behavior, and stability is discussed.

Synthesis and Characterization of Poly(vinylcaprolactam)-Based Microgels Exhibiting Temperature and pH-Sensitive Properties

Abstract: Novel temperature- and pH-responsive microgels based on poly(vinylcaprolactam-co-acetoacetoxy methacrylate) (VCL/AAEM) functionalized with vinylimidazole (VIm) has been prepared in aqueous medium using simple batch dispersion polymerization procedure. Obtained microgel particles are characterized by narrow particle size distribution and their hydrodynamic radius can be varied from 200 to 500 nm (pH = 6, T = 20 °C). The T- and pH-sensitivity of obtained particles can be easily tuned by the variation of the Vim content in the copolymer structure. Increase of VIm content in the microgel structure led to increased swelling of the microgels in acidic medium and strong shift of the volume phase transition temperature to higher temperatures. It has been found that sedimentation behavior of obtained microgels is strongly pH-dependent, and this effect can be used for controlled particle separation.

Hybrid Microgels with ZnS Inclusions

Abstract: We report on a preparation of hybrid microgels filled with ZnS inclusions. Temperature-sensitive poly(N-vinylcaprolactam-co-acetoacetoxyethyl methacrylate) (VCL/AAEM) microgels have been used as containers for deposition of ZnS by reaction of zinc acetate and thioacetamide under ultrasonic agitation. ZnS was deposited directly into microgels, leading to formation of composite particles which exhibit temperature-sensitive properties, high ZnS contents, and excellent colloidal stability. The influence of ZnS load on microgel size, morphology, swelling−deswelling behavior, and stability is discussed. Hybrid particles contain up to 20 wt % of ZnS, and particle stability decreases with increase of inorganic filler content. Detailed microscopy investigations confirm incorporation of ZnS nanoparticles into microgel network. The possibility of self-assembly of hybrid particles on different surfaces was studied. It has been found that microgels filled with ZnS can form organized particle arrays after water evapora...

Magnetism and microfluidics

Abstract: Magnetic forces are now being utilised in an amazing variety of microfluidic applications. Magnetohydrodynamic flow has been applied to the pumping of fluids through microchannels. Magnetic materials such as ferrofluids or magnetically doped PDMS have been used as valves. Magnetic microparticles have been employed for mixing of fluid streams. Magnetic particles have also been used as solid supports for bioreactions in microchannels. Trapping and transport of single cells are being investigated and recently, advances have been made towards the detection of magnetic material on-chip. The aim of this review is to introduce and discuss the various developments within the field of magnetism and microfluidics.

Thermoresponsive Polymers for Biomedical Applications

Abstract: Thermoresponsive polymers are a class of “smart” materials that have the ability to respond to a change in temperature; a property that makes them useful materials in a wide range of applications and consequently attracts much scientific interest. This review focuses mainly on the studies published over the last 10 years on the synthesis and use of thermoresponsive polymers for biomedical applications including drug delivery, tissue engineering and gene delivery. A summary of the main applications is given following the different studies on thermoresponsive polymers which are categorized based on their 3-dimensional structure; hydrogels, interpenetrating networks, micelles, crosslinked micelles, polymersomes, films and particles.

Thermosensitive core--shell particles as carriers for Ag nanoparticles : modulating the catalytic activity by a phase transition in networks

Abstract: Metal nanoparticles have properties that are significantly different from the bulk properties of the metals. Moreover, their high surface-to-volume ratio renders them ideal candidates for application as catalysts. However, the pronounced tendency of nanoparticles to aggregate must be overcome by using suitable carrier systems. Recently, a number of systems have been discussed that are suitable for applications in aqueous environments. These include polymers, dendrimers, microgels, 18] and other colloidal systems. 20] In all the cases studied so far, these carrier systems only provide a suitable support for the nanoparticles and prevent them from aggregating. In this way the carrier system of, for example, dendrimers or microgels acts much in the same way as a “nanoreactor” that immobilizes the particles and leads to their more convenient handling. Here we report on the first system that allows us to modulate the activity of nanoparticles through a thermodynamic transition that takes place within the carrier system. Figure 1 displays the principle. Metallic nanoparticles are embedded in a polymeric network attached to a colloidal core particle. In all the cases discussed here the core consists of poly(styrene) (PS) while the network consists of poly(Nisopropylacrylamide) (PNIPA) cross-linked with N,N’-methylenebisacrylamide (BIS). The particles are suspended in water, which swells the PNIPA at room temperature. The PNIPA network, however, undergoes a phase transition around 30 8C, during which most of the water is expelled. Previous experiments have demonstrated that this transition is perfectly reversible and the process of shrinking and reswelling can be repeated without degradation or coagulation of the particles. Metallic nanoparticles embedded in such a network are fully accessible to reactants at low temperature. Above the phase transition, however, the marked shrinkage of the network should be followed by a concomitant slowing down of the diffusion of the reactants within the network. The rate of reactions catalyzed by the nanoparticles should thus be slowed down considerably. In this way, the network could act as a “nanoreactor” that can be opened or closed to a certain extent. Herein we demonstrate that thermosensitive core–shell networks may indeed be used as such a nanoreactor. The activity of the catalyst can be modulated by temperature over a wide range. As the model reaction we chose the reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride. The reaction was repeatedly performed to check the catalytic activity of the metal nanoparticles, and the results obtained in the present study can be directly compared to literature data. The carrier particles having a PS core and a PNIPA shell were prepared as described recently. 24] Figure 2 shows a schematic representation of the silver nanoparticles being

Review on Hydrogel-based pH Sensors and Microsensors.

Abstract: Stimuli-responsive hydrogels are materials with great potential for development of active functionalities in fluidics and micro-fluidics. Based on the current state of research on pH sensors, hydrogel sensors are described qualitatively and quantitatively for the first time. The review introduces the physical background of the special properties of stimuli-responsive hydrogels. Following, transducers are described which are able to convert the non-electrical changes of the physical properties of stimuli-responsive hydrogels into an electrical signal. Finally, the specific sensor properties, design rules and general conditions for sensor applications are discussed.

Stimuli-responsive polymer gels

Abstract: Stimuli-responsive polymer gels have received considerable attention due to their singular mechanical properties, which make them materials of choice for niche applications. Polymer gels comprising either physical or chemical cross-links can undergo controlled and reversible shape changes in response to an applied field. The stimulus or external field applied may include thermal, electrical, magnetic, pH, UV/visible light, ionic or metallic interactions or combinations thereof. The shape change can manifest itself in two-dimensional actuation, bending motion, or three-dimensional actuation, volume change. This reversible contraction and expansion of polymer gels as well as their mechanical properties are similar to that of biological muscles. This review will describe and critique some of the recent advances in the field of stimuli-responsive polymer gels including the design of new classes of polymeric gels, controlled actuation in response to external stimuli, and ability to tailor material properties for different applications.