Authors:Isabelle Kraus, Shuning Li, Andrea Knauer, Marc Schmutz, Jacques Faerber, Christophe A. Serra and Michael Köhler
This paper presents a new route to the synthesis of uniform and size-controlled inorganic/organic composite microparticles by means of microreaction technology. Au-nanoparticles in the range of 3 to 14 nm are synthesized by reduction of tetrachloroauric acid, while ZnO-nanoparticles (200–2000 nm) are synthesized in a continuous-flow two-step process using microtube arrangements for microsegmented flow. Both inorganic nanoparticles have a well-controlled size and narrow size distribution. Upon surface modification, the nanoparticles are then mixed on one hand with an acrylate-based monomer and, on the other hand, with an aqueous solution of acrylamide. Both solutions were then emulsified into uniform core-shell droplets by means of a capillary-based microfluidic device. Droplet's shell was hardened through UV-induced polymerization, whereas the core led to a hydrogel upon thermal-induced polymerization. Core-shell polymer microparticles (200–300 µm) with inorganic nanoparticles selectively incorporated into the core and the shell are thus obtained as proven by extensive morphological characterizations using electronic and optical microscopies.
Authors:Dambarudhar Parida, Christophe A. Serra, Rigoberto Ibarra Gómez, Dhiraj K. Garg, Yannick Hoarau, Michel Bouquey and René Muller
We report on the synthesis of 2-(dimethylamino)ethyl methacrylate by atom transfer radical polymerization (ATRP) in tubular microreactors. Different process parameters, temperature, pressure, and shear rate, were considered to accelerate the reaction. Increase in temperature induced a faster reaction, but controlled nature of ATRP decreased past a threshold value that can be increased up to 95 °C by reducing the residence time. Positive effect of pressure was observed since significant increases in monomer conversion (+12.5 %) and molecular weight (+5,000 g/mol) were obtained. Moreover, polydispersity index was found to decrease from 1.52 at normal pressure to 1.44 at 100 bars. Benefit of pressure was more visible in smaller reaction space (smaller tube diameter). Finally, shear rate has quite an influence on the early stage of the polymerization and is expressed by an increase in the reaction rate. However, the effect was dimed for long residence times.
Authors:Christophe A. Serra, Ikram U. Khan, ZhenQi Chang, Michel Bouquey, René Muller, Isabelle Kraus, Marc Schmutz, Thierry Vandamme, Nicolas Anton, Christian Ohm, Rudolf Zentel, Andrea Knauer and Michael Köhler
Capillary-based flow-focusing and co-flow microsystems were developed to produce sphere-like polymer microparticles of adjustable sizes in the range of 50 to 600 μm with a narrow size distribution (CV < 5%) and different morphologies (core-shell, janus, and capsules). Rod-like particles whose length was conveniently adjusted between 400 μm and few millimeters were also produced using the same microsystems. Influence of operating conditions (flow rate of the different fluid, microsystem characteristic dimensions, and design) as well as material parameters (viscosity of the different fluids and surface tension) was investigated. Empirical relationships were thus derived from experimental data to predict the microparticle's overall size, shell thickness, or rods length. Besides morphology, microparticles with various compositions were synthesized and their potential applications highlighted: drug-loaded microparticles for new drug delivery strategies, composed inorganic-organic multiscale microparticles for sensorics, and liquid crystalline elastomer microparticles showing an anisotropic reversible shape change upon temperature for thermal actuators or artificial muscles.