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The purpose is to present the application of the acoustic levitation as a model system for a coating process with non-spherical and light particles in the fluidized bed reactor. An acoustic levitator has been used to track a pellet in a contactless position by Raman spectroscopy, while it was coated with polyvinylpyrrolidone by an ultrasonic nozzle. The Raman data were evaluated by a principal component analysis and a multivariate curve resolution. The pellets had a maximum size of 1.0 mm. To develop an optimization model, a design of experiments was performed in the acoustic levitator. The obtained optimization model demonstrated that the mass fraction of polyvinylpyrrolidone in the coating solution, the temperature and the optional air stream affected the coating thickness. To validate the optimization model, the pellets were coated in the acoustic levitator and in a fluidized bed reactor under the same conditions. The coated pellets had similar morphologies.

The aim of the current study is to optimize the bed fluidized coating process of mini tablets by means of an acoustic levitator. The optimized coating parameters, which have to be set in a fluidized bed reactor, can be determined by means of contactless levitation of a single mini tablet in an acoustic levitator equipped with an ultrasonic atomizer. Mini tablets were positioned in a contactless way in the levitator and coated with polyvinylpyrrolidone (PVP) solution. The influences of process parameters on the coating, such as temperature, mass fraction, volumetric flow rate and spray time, are analyzed in an acoustic levitator in a cost- and time-saving manner. The results from the acoustic levitator were comparable to those performed in a fluidized bed reactor. A design of experiments was performed to analyze the effects of those parameters on the mass of coating thickness. The surfaces of the samples coated in the acoustic levitator at 40 °C were comparable to samples coated in a fluidized bed reactor at 40 °C by using scanning electron microscopy (SEM).

The introduction of functional groups into microparticles is commonly accomplished through, at times, low-yielding post-synthesis modification. In this detailed study, the introduction of azide functionality into uniform, crosslinked, macroporous microparticles through direct copolymerization of styrene, divinylbenzene (DVB), and 4-vinylbenzyl azide (VBA) in varying ratios inside swollen polystyrene seed (template) particles is investigated. Formulations contained up to 40 wt% of VBA in the monomer mixture. Resulting microspheres were characterised by SEM, porosimetry, FT-IR spectroscopy, and CHN elemental analysis. Uniform spherical particles with diameters ranging from 7.3 to 10.8 μm with diameter dispersities typically below 1.01 and with tuneable azide loadings from 0.11 to 1.17 mmol g−1 were obtained. Interestingly, severe effects of VBA addition on porosity, surface smoothness, and particle shape were observed. Specific surface areas and cumulative pore volumes increased with the amount of DVB in feed, decreased with increasing VBA feed ratio, and increased drastically for the use of azide-functional template particles with measured cumulative pore volumes reaching up to 0.60 cm3 g−1. With increasing VBA feed, formation of smaller, secondary particles was observed and attributed to an incomplete swelling of VBA into seed particles, which is discussed as a main reason for lower-than-expected azide contents in product particles. For high VBA feed ratios (>25 wt%), dented, hollow, or hollow collapsed azide-functional particles were found, presumably due to immiscibility of the growing azide-functional copolymer with the polystyrene seeds. Finally, successful click-modification is demonstrated with phenylacetylene and an alkyne-functional Rhodamine B dye allowing for mapping of functionalization density through confocal fluorescence microscopy.

Electrospun polybutadiene (BR) was crosslinked in situ during the spinning process to obtain stable fibers. Crosslinking was induced by addition of photoinitiator to the electrospun BR solution. Due to the very low glass transition temperature (Tg) of BR (below −80 °C) it is necessary to crosslink the fibers thereby improving the mechanical properties and creating stable fibers by preventing fibers from melting together. In order to prevent the polymer fibers from melting onto the grounded collector, a solution of sodium chloride in methanol was used to collect the fibers thereby letting the fibers float and increase the irradiation time of the UV curing during the electrospinning process. Subsequent surface modification via thiol-ene click chemistry on remaining C C bonds was successfully employed with mercaptoethanol or thioglycolic acid, leading to superhydrophilic fiber mats.